TM 11-5826-225-35

DEPARTMENT OF THE ARMY TECHNICAL MANUAL

DS, GS, AND DEPOT

MAINTENANCE MANUAL

DIRECTION FINDER SET AN/ARN-83

This copy is a reprint which include s

pages from changes 1 thru 5 .

HEADQUARTERS , DEPARTMENT OF THE ARM Y
CAUTION

This equipment is transistorized. Before making resistance measurements on the circuits,

read the instructions in Paragraphs 2-2 and 2-8.
TM 11-5826-225-35

C 5 Change

No 5 HEADQUARTERS

DEPARTMENT OF THE ARMY

Washington, DC, 3 July 1980

Direct Support, General Support

and Depot Maintenance Manual

DIRECTION FINDER SET AN/ARN-83

(NSN 5826-00-912-4415)

TM 11-5826-225-35, 17 March 1966, is changed as follows:

1. Remove and insert pages as indicated in the page list below.

Remove Insert

i. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i

1-1 and 1-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-1 and 1-2

1-5 and 1-6 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-5 and 1-6

l-13t hrough l-16 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l-l3through l-l6

l-19 and l-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1-19 and l-20

l-22.1 and l-22.2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l-22.1 and 1-22.2

l-27 through l-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . l-27 through 1-30

2-7 through 2-10 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-7 through 2-10

2-29 through 2-34 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2-29 through 2-34

2-39 through 2-42 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2- 39 through 2-42

3-19 and 3-20 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3-l9 and 3-20

3-23 through 3-28 ... . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . . ..3-23 through 3-3l

4-13 through 4-14.4 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4-13 through 4-14.l

4-25 and 4-26 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-25 and 4-26

4-29 and 4-30 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..4-29 and 4-30

5-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-1

5-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ... . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-5

5-12.7 . . . . . . . . . . . . . . . . . . . . . . ...... . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-12.7

5-12.9 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-12.9

5-12.11 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-12.11

5-12.13 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-12.13

5-12.15 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-12.15

5-12.17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . , . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..5-12.17 

5-12.19

5-12.21

5-12.23

5-12.25

5-12.27

5-12.29

5-14 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-14

5-17 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ...5-17

I-l ard I-2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .. I-l and I-2

2. File this change sheet in front of the manual for reference purposes.
By Order of the Secretary of the Amry:

Official:

J. C. PENNINGTON

E. C. MEYER

General, United States Army

Chief of Staff

Major General, United States Army

The Ajudant General ‘

Distribution:

To be distributed in accordance with DA Form 12-36, Direct and General Support maintenance requirements for AN/ARN-83
TM 11-5826-225-35

C4

C HANG E

No. 4

}

HEADQUARTERS

DEPARTMENT OF THE ARMY

WASHINGTON, DC 20 September 1978

Direct Support, General Support

and Depot Maintenance Manual

DIRECTION FINDER SET AN/ARN-83

(NSN 5826-00-912-44151

This Change current as of 23 May 1978

TM 11-5826-225-35, 17 March 1966, is changed as follows:

1, Title of the manual is changed as shown above.

2. New or changed material is indicated by a vertical bar in the margin.

3. Remove and insert pages as indicated in the page list below.

Remove Insert

1-1 and 1-2 1-1 and 1-2

1-7 and 1-8 1-7 and 1-8

2-1 through 2-4 2-1 through 2-4

2-35 and 2-3 6 .2-35 and 2-36

3-27 and 3-28

3-27 and 3-28

4-5 through 4-6.1I 4-5 through 4-6.1

4-1 1 .4-11

4-15 and 4-16 . 4-15 and 4-16

4-23 through 4-28 .4-23 through 4-28

4. File this change sheet in front of the manual for reference p urposes.

By Order of the Secretary of the Army:

BERNARD W. ROGERS

General,United States Army

Official: Chief of Staff

J. C. PENNINGTON

Brigadier General, United States Army

The Adjudant General

Distribution:

To be distributed in accordance with DA Form 12-36, organizational maintenance requirements for

AN/ARN-83.

TM 11-5826-225-35

Technical Manual HEADQUARTERS

DEPARTMENT OF THE ARMY

No. 11-5826-225-35 Washington, D.C., 17 March 1966

Direct Support, General Support, and Depot Maintenance Manual

DIRECTION FINDER SET AN/ARN-8 3

page

Chapter 1

Section I.

II

III.

IV.

Chapter 2.

Section I

II.

III.

IV.

V.

Chapter 3

Section I.

II.

Chapter 4

Section I

II.

Chapter 5.

Index

FUNCTIONING

General functioning of Direction Finder Set AN/ARN-83

Detailed functioning of Radio Receiver R-1391/ARN-83

Detailed functioning of additional equipments

Interunit circuit functioning

TROUBLE SHOOTING

General troubleshooting techniques

Troubleshooting Radio Receiver R-1391/ARN-83

Troubleshooting Direction Finder Control C-6899/ARN-83

Troubleshooting Mounting MT-3605/ARN-83 and Inverter, Power, Static

CV-2128

Troubleshooting Antenna AS-1863/ARN-83

REPAIR AND ALIGNMENT

Repairs

Alignment

GENERAL SUPPORT AND DEPOT INSPECTION PROCEDURES

General support

Depot Inspection standards

ILLUSTRATIONS

Paragraph

1-1 –1-3

1-4 –1-21

1-22– 1-25,

1-26– 1-32

2-1 –2-3

2-4 -2-9

2-10 -2-12

2-13 -2-15

2-16

3-1 -3-7

3-8 -3-22

4-1- 4-19

4-20- 4-21

1-1

1-5

1-22

I-25

2-1

2-3

2-35

2-40

2-43

3-1

3-19

4-1

4-29

5-1

1-1

Change 5 i

TM 11-5826-225-35

CHAPTER 1

FUNCTIONING

Section 1. GENERAL FUNCTIONING OF DIRECTION FINDER SET AN/ARN-83

1-1. Scope

This manual contains direct support, general support

and depot maintenance instructions for Direction

Finder Set AN/ARN-83, It includes instructions appropriate to these levels of maintenance for

troubleshooting, testing, aligning, and repairing the

equipment. The manual also lists tools, materials, and

test equipment for maintenance. Detailed functions of

the equipment are also covered.

 1-1.1. Reporting Equipment lmprovement Recommendations (EIR)

EIR’s wll be prepared using DA Form 2407, Maintenance Request. Instructions for preparing EIR’s are

provided in TM 38-750, The Army Maintenance

Management ( System. EIR’s should be mailed direct to

Commander, US Army Communications and

Electronics Materiel Readiness Command, ATTN:

DRSEL-MA-Q, Fort Monmouth, N.J. 07703. A reply

will be sent direct to you.

NOTE

For other applicable forms and records, see

paragraphs 1-2 and 1-3 in TM

11-5826-225-12.

1-2. General System Block Diagram

Functioning

U. Direction Finder Set AN/ARN-83 includes the

components shown in figure 1-1. The general direction

of ac power, dc power, and signal flow is also shown.

Antenna AS- 1863/ARN-83 (fixed loop antenna) contains two pairs of loop antennas displaced 90 degrees.

One pair of loops is sensitive to radio signals parallel to

the aircraft longitudinal axis, and the other pair of loops

is sensitive to signals parallel to the aircraft lateral axis.

The two-loop output signals are applied to Radio

Receiver R- 1391/ARN-83 through an RF inductance

compensator (not supplied as part of direction finder

set) which corrects for any electromagnetic field distortion induced into the antenna by metal parts of the

Aircraft.

b. Radio Receiver R-1391/ARN-83 (CPN 522-

2587-000, -0150 ) receives directional radio signals

from Antenna .AS-l863/ARN-83 and nondirectional radio signals from a sense antenna (not

c. Direction Finder Control C-6899 /ARN-83 contains all the necessary controls for remotely selecting

the receiver frequency ranges (190-400 kc, 400-850

kc, 850-1750 kc) and operating modes (adf, antenna,

or loop), tuning the receiver, adjusting gain, and controlling power bfo operation.

d. Mounting MT-3605/ARN-83, serves as the

receiver shockmount and distribution center for ac and

dc power, control signals, audio signal, and bearing

data, between the receiver and control unit and the

aircraft. Inverter, power, static CV-2128/ARN-83, a

dc-to-ac inverter in the receiver shockrnount, changes

27.5-volts dc primary power into 26-volts, 400-cps

power for synchro excitation.

1-3. Overall Functional Block Diagram

Analysis

The following is based upon the overall

Change 5 1-1
TM 11-5826-225-35

Figure 1-1. Direction Finder Set A N/A R N-83 ,

system block diagram.

functional block diagram in figure 5–2. This

diagram shows the equipment signal paths and

methods of remote tuning, frequency range

selection, and operating mode (function) selection from the control unit.

a. Operating Mode Control Signal Paths. The

receiver frequency ranges ( 190-400 kc, 400–

850 kc, 850–1750 kc) and operating modes ( adf,

antenna, loop), are selected by motor B2 which

rotates frequency range and function switch

S1 through an Autopositioner circuit. Rotary

switch S1, containing a number of sections,

combines both range and function selection into

one switch. Electrical circuits are completed

between motor B2 and switches S302 and S304.

For each of the three operating positions (adf,

antenna, or loop) of function switch S302,

switch S1 will rotate and stop on nine possible

1-2

positions depending on where range switch

S304 is positioned. Since switches S302 and

S304 may each be set to three different positions, it requires nine positions of switch S1

(three positions for each operating mode) to

cover all frequency ranges and Operating

modes.

Paths (fig, 5-2),

(1) Radio signals induced in Antenna AS1863 ARN–83, are impressed on the

stator windings of resolver B3. The

direction finder set uses a resolver

operating as a goniometer rather than

using a rotating loop antenna. Rotating the resolver rotor produces a rotating figure-eight RF pattern the

same as rotating a loop antenna. The
TM 11-5826-225-35

angular position of the resolver rotor

with respect to its stator windings and

relative bearing of the radio station,

determines the phase and amplitude

of RF signal applied to first RF

amplifier Q1. Resolver 133 driving

bearing synchro transmitter B4 is

part of a closed-loop servo system.

During adf operation, servo motor B5

runs B3 in one direction or the other

until the servo loop error voltage

drops to a minimum. At this point

resolver B3 will stop on a null.

(2) Before reaching second RF amplifier

Q3, the RF signal output of Q1 passes

through a 90-degree phase shift network which insures that the loop antenna and sense antenna RF signals

will be in phase or 180 degrees out of

phase. The RF output of amplifier Q3

is coupled to balanced modulator CR15

and CR16. Modulation is supplied by

two phases of 110-cps signals derived

from 110-cps oscillator Q22. The balanced modulator output signal, applied

to a sense antenna signal mixing network in push-pull RF amplifier Q2

and Q4, is a double-sideband signal

containing upper and lower 110-cps

sidebands with the RF carrier absent.

After adding the sense antenna RF

1-3
TM 11–5826-225–35

c. Loop Operating Mode Signal Paths (fig.

5-2)

1-4

(fig. 5-2)

 (fig.

5-2)
TM 11-5826-225-35

Section Il. DETAILED FUNCTIONING OF RADIO RECEIVER R–1391/ARN-83

1-4. General

Radio Receiver R–1391/ARN–83, is the main

operational unit of Direction Finder Set (AN/

ARN-83. The receiver is a single-conversion

superheterodyne low frequency receiver, tunable from 190 kc to 1750 kc in three ranges. In

automatic direction finding ( adf ) mode, it processes RF input signals from a directional loop

antenna (fixed ) and a nondirectional sense antenna to determine the hearing of radio stations. The loop antenna RF output is impressed

on the stator windings of a resolver ( goniometer) driven by a closed loop servo mechanism.

A phase comparison between RF signals, from

the resolver rotor winding and the sense antenna signals, determines whether the resolver

rotor electrical zero or null position is either to

the right or left of the direction of radio station signals. After this is determined, the servo

mechanism rotates the resolver in the direction

required to reach a null, which is the direction

of the radio station. A synchro transmitter,

geared to the resolver, transfers bearing data to

the aircraft bearing indicator. The Mock diagram illustrated in figure 5-2, shows the relationship of all functional circuits in the receiver. The following paragraphs contain detailed

circuit functions in the same order as the direction of signal flow depicted in figure 5-2. A

complete Schematic of the receiver is shown in

figures 5-10.1,5-10.2, 5-10.3, and 5-10.4.

1-5. Receiver Loop Antenna and

Goniorneter Circuit Functioning

(fig. 5-3)

a. Antenna AS-1863/ARN-83, comprises two

fixed loop antennas mounted at right angles to

each other with loop 2 sensitive to radio signals

along the aircraft longitudinal axis and loop 1

sensitive to radio signals along the aircraft lateral axis. Each loop antenna is terminated in a

stator winding of resolver B3. The rotor (L3)

of B3 is mechanically coupled to a servo mechanism capable of rotating it through 360 de

grees with its coupling to L1 and L2 varied accordingly. The combination of Ll, and, and L3,

is called goniometer. Assume that loop 1 is

along a line directly north and south, and loop

2 is along the east-west line. If a radio station

RF source is north of loop 2, maximum signal

will be induced in loop 2 and minimum signal in

loop 1 (fig. 1–2). A current will flow in winding

L2 of resolver B3 and none will flow in L1. If

the rotor (L3) of B3 is rotated so that maximum coupling to L1 occurs, no signal will be

induced in L3 and if a pointer was attached to

the rotor of B3 (assuming proper orientation),

one end of the pointer would indicate O degrees

(north) on a 360-degree dial and the other end,

would point 180 degrees or south. If the direction of a radio station is at a bearing of 135

degrees (fig. 1–2), the bearing is not perpendicular to the plane of either loop 1 or loop 2. This

will induce a signal voltage in each loop with a

phase difference of 180 degrees and equal signal

amplitudes. Maximum signal will be induced in

the rotor winding of B3 when it is coupled to

either L1 or L2 and minimum signal output will

result when the rotor apparent null is positioned for minimum coupling to both L1 and

L2. The resolver functions as a miniature rotating figure-eight loop antenna pattern and the

Change 5 1-5
TM 11-5826-225-35

l-6

TM 5826-22S-35-4

Figure 1-2
TM 11-5826-225-35

phase of RF output shifts 180° as the null

points are crossed, accomplishing identical results as a rotating loop antenna. Figure 1–2

shows the relative phase and magnitude of

loop antenna signals for different radio station

bearings.

b. The rotor winding output signal of resolver B3 is connected in push-pull to the

grounded center tap primary of RF transformer Tl, T2, or T3, depending on the position

of frequency range and function switch wafer

S1–F. Switch S1 is motor-driven through an

autopositioner system (para 1–24). Rear switch

wafer S1–G, switches the proper center-tapped

secondary windings of Tl, T2, or T3 to variable

tuning capacitor Cl–B and the base of Q1.

Front switch wafer S–lG, connects unused

transformer secondary windings to B+. Trimmer capacitors C2, C3, and C4 adjust frequency ranges at the high end of the range

and slug adjustments in RF transformer secondaries set the low end of ranges. Resistors

R1 and R2 supply bias to Q1 through the transformer secondaries and rear switch wafer SlG. The resolver RF output signal of Q1 is applied to second RF amplifier stage Q3 through

a phase shift network.

1–6. Phase Shift Network and Second RF

Amplifier

(fig. 5-4)

(para 1-7).

1 –7. Balanced Modulator

(fig. 5-4 )

b. In figure 5–4, the amplifier resolver RF

Change 4 1–7
TM 11-5826-225-35

TM5826-225-35- 6

Figure 1-3. Balanced modulator waveforms.

1-8 Change 1
fig. 1-3

figure 1-3

TM 11–5826-225-35

d. The waveforms in figure 1–3 shows sigin figure 1–3. It will be observed that for a radio

of diode CR15 (fig. 5–4) into the secondary of

modulation envelope as shown in figure 1–3. The

out the 90° phase shift network (fig. 5–4) and

1–8. Sense Antenna Input Network

(fig. 1-4)

Change 1 1–9
TM 11-5826-225-35

Figure 1-4. Sense antenna and balanced modulator signal mixing network, schematic diagram.

wafer S1-R substitutes C138 in place of the J1 is used. The sense antenna signal is then

antenna to prevent any detuning effects. impressed on terminal 8 (a higher impedance

b. If the sense antenna and cabling has a tap from ground) of an RF transformer

capacity of 150 micromicrofarads, pin E of through switch wafers S1-R (front) and S1-

1-10 Change 1
TM 11–5826-225-35

c. In antenna operating mode, only the sense

antenna is used and no signal appears on the

RF transformers primaries. In loop operating

mode, switch wafer S1–N grounds the sense

antenna inputs and the resolver RF output

signal, shunted on one side of the balanced

modulator (fig. 5-4), appears as a singleegded signal on segment Z of rear switch

wafer S1–0. This RF signal is applied to terminal 4 of a switched transformer primary.

1-9. Push-Pull RF Amplifier

(fig. 5-5)

dc bias is fixed and RF gain cannot be manually controlled. In all operating modes, base

and emitter voltages are controlled by an age

voltage applied through R14 and R135. Balance adjustment R136 balances emitter currents of Q2 and Q4. The push-pull RF output

signals of Q2 and Q 4 are applied to the centertapped primary of T107, T108, or T109.

1-10. Mixer Input Tuned Circuits

(fig. 5-6)

Change 1 1–11
TM 11-5826-225-35

1–11. Local Oscillator

(fig. 5-7)

1–12. Mixer

(fig. 5-7)

1-12 Change 1

1–13. IF Amplifiers

a. First and Second IF Amplifiers (fig. 1–5).

b. Third, Fourth, and Fifth IF Amplifiers

(fig. 5-8). The circuitry of IF amplifiers Q9,

Q10, and Qll is similar to the first and second

IF amplifiers, with the exception that amplifier

gain is fixed with emitter and base bias voltages and cannot be controlled automatically

or manually. After the 142.5-kc signal has been

amplified in the second IF amplifier, it is

further amplified by Q9, Q10, and Qll, and
TM 11-5826-225-35

Figure 1-5.

applied to the audio detector (para 1-14). A t

the output of IF transformer T17, a 142.5-kc

signal is rectified by meter rectifier CR10 and

applied through resistor R40 to tuning meter

M301 in the control unit for signal level indication. A second 142.5-kc signal, taken from

T17, is used for developing age voltage (para

1-16).

1–14. Bfo, Detecter, and Limited,

(fig. 1-6)

Change 5 1-13
TM 11-5826-225-3 5

Figure 1-6. Adio detector, limiter, and bfo, schematic diagram.

1-15. Audio Amplifiers

(fig 1–7)

1–16. Automatic Gain and

Receiver Muting

(fig. 1-8)

1–14 Change 1
TM 11-5826-225-35

Figure 1–7. Audio amp[ifier, Schematic diagram,

chronous filter (para 1–17).

Change 5 1-15
TM 11-5826-225-35

1-17. 110-Cps Variable Phase Signal and

Synchronous Filter

(fig. 1-9)

a. The 110-cps variable phase signal and

other audio frequencies modulating the 142.5-kc

IF amplifier frequency, are detected by age rectifier CR3 and applied to the base of first age

amplifier Q16. In addition to serving as an age

rectifier for audio frequencies (para 1-16),

diode CR3 also detects the 110-CPS variable

phase modulation envelope originally developed

in the balanced modulator (para 1–7). The 110-

cps signal output of CR3 appearing in the same

phase on the emitter of Q16, is applied through

R145, C75, R66, and C125 to the servoamplifier

furnishing power for the servo motor geared to

a resolver. Since undesirable audio frequencies

other than 110 cps may be present, a 110-cps

synchronous filter is used to remove these frequencies.

b. Transistors Q19 and Q20 operate as an

electronic switch gated and synchronized by two

opposite phases of 110-CPS sine wave signals derived from a 11O-CPS oscillator. The synchronous filter causes the junction connection of capacitors C76 and C77 to assume the characteristics of an LC filter tuned to a center frequency

of 110 cps. There is maximum signal transfer

at 110 cps with response falling off at frequencies above or below this frequency.

c. The phase of the 110-CIM signal applied

through capacitors C76 and C77 to the collectors

of Q19 and Q20 may be in-phase, or out-ofphase, with either one of the 110-cps signals

applied to the bases of Q19 and Q20, Assume

that phase 1 on the base of Q20 is positivegoing, and phase 2 on Q19 is negative-going.

Every half cycle, these phases will change while

the 110-cps variable phase signal may or may

not change phase at the same time. If the 110-

cps variable phase signal on capacitor C77 is

positive-going and in phase with phase 1 of the

110-cps signal on the base of Q20, transistor

Q20 will conduct current from emitter to collector and charge capacitor C77 until either

phase 1 of the 110-CPS signal reverses or the

110-cps variable phase signal changes phase.

During the charging cycle, the emitter-to-collector resistance of Q20 is low, and the current

flowing from negative (ground) to positive

Figure 1-8. Receiver agc and muting circuit,

schematic diagram.

1-16 Change 5
TM 11-5826-225-35

Change 1 1-1 7
(para 1-7)

(fig. 5-9)

figure 5-9,

1-18.

TM 11-5826-225-35

Figure 1-9,

1–18 Change 1
1-19. 110-cps Oscillatcor and Amplifier

(fig. 1-10)

U. The 110-CPS oscillator Q22 supplies two

separate phases of 110-cps signals for the

110-cps synchronous filter ( para 1–17) and

for using the control unit loop switch to manually rotate the receiver in loop mode (para

1-18). The 110-CPS amplifier Q23 provides

single-phase, 110-CPS voltage for energizing

the reference phase winding of resolver servo

motor B5 (fig. 5-9).

b. Transistor oscillator Q22 is a modified

Hartley oscillator. The feedback necessary to

sustain oscillation is established from collector

to base through impedance network L32, C151,

and C153. The grounded center-tapped inductor L32 provides a 180-degree phase shift

in collector output signal at the 110-CPS

resonant frequency established by the parallel

resonant tuned circuit of L32, C151, and C153.

The 110-cps signal fed back to the base of

Q22 through C9 and L24 is of the proper phase

to cause oscillation. The 110-CPS oscillator operates in adf and loops modes only, In antenna

mode, rear switch wafer S1-K removes emitter

and base bias voltages. The 110-cps collector

output signal of Q22 is amplified by 110-cps

amplifier Q23 to supply sufficient current for

Change 5 1-19
TM 11-5826-225-35

Figure 1-10.

1-20. Tuning Servoamplifiers

(fig. 1-11)

1-20 Change 1
TM 11–5826-225-35

1-21. Voltage Regulator

(fig. 1-12)

Change 1 1-21
TM 11–5826-225-35

Figure 1–11.

1-22 Change 1
TM 11-5826-225-35

TM5826-225-35-CI-2 0

Figure 1-12. Regulated dc power supply,

schematic diagram.

Section Ill. DETAILED FUNCTIONING OF ADDITIONAL EQUIPMENTS

1-22. General

1-23. Inverter, Power, Static CV-2128/

ARN-83

(fig. 1-13)

The inverter circuit changes 27.5 volts dc to

26 volts, 400 cps ac for motor generator MG1

and synchro B4 in the receiver and B301 in the

control unit. The inverter comprises 400-cps

oscillator Q1 coupled to a push-pull amplifier

Change 1 1-22.1
Figure 1-13.

TM 11-5826-22-35

1-22.2 Change 5
Figure 1-14.

Figure 1-15.

TM 11-5826-225-35

1-23
Figure 1-16.

TM 11-5826-225-35

1-24
TM 11-5826-225-35

1 –24, Antenna AS-1863/ARN–83

(fig. 1-14)

Antenna AS–1863/ARN–83 consists basically

of four ferrite-cored coils, two of which are

parallel to the longitudinal axis of the aircraft and two are perpendicular to this line.

Each set of physically parallel coils is connected in parallel to provide maximum gain. The

antenna provides the basic information necessary to determine the direction of the received

signals. Refer to paragraph 1–5 for a discussion on how this is accomplished. An RF inductance compensator is required between the

loop antenna and the receiver to compensate

for the deflection of arriving radio signals by

the fuselage of the aircraft. For this reason the

RF inductance compensator is selected during

installation. Figure 1–15 is a schematic diagram for a typical RF inductance compensator.

1-25. Direction Finder Control

C-6899/ARN-83

Detailed functioning of the control unit is

contained in section IV of this chapter. Section

IV describes interunit circuit functioning. Figure 5–11 is the schematic diagram for the

control unit.

Section IV. INTERUNIT CIRCUIT FUNCTIONING

1–26. General

Interunit functions are included in this section to provide an understanding of certain

interrelations between the control unit and receiver in various types of operation. Such

knowledge will enable maintenance personnel,

when troubleshooting, to sectionalize troubles

to a defective unit and, in some cases, to localize trouble to a defective part within a unit.

Circuit functioning of components in the control unit and receiver is discussed only where

individual circuits are interconnected in a common circuit,

1-27. Function and Frequency Range

Selection

(fig. 5-12)

selection in the receiver is accomplished

through the interunit autopositioner circuit

illustrated in figure 5–12. The function and

range-switching mechanism in the receiver

consists of a motor-driven, multisection switch

combining both function and range selection

into one ganged switch. Since the control unit

function switch has three operating mode positions (ADF, ANT, and LOOP) requiring three

frequency range positions of range switch

S304 for each operating mode, it requires nine

positions of the receiver motor-driven stwitch

to select all operating modes and frequency

ranges. In the receiver, switch wafers S1-M

through S1–R are 12-position switches having

nine effective switch positions over three sectors or quadrants of the switches (leaving

three blank positions). Each switch wafer is

divided into three equal areas or sectors with

Change 1 1-25
fig. 5-12)

TM 11-5826-225-35

1–28. Receiver Tuning

(fig. 5-13)

1-26 Change 1
excitation and MC1, is derived from a dc-to-ac

voltage inverter located in the receiver mount.

All electrical connections between the control

unit and receiver are made through the receiver mount and airframe cabling.

1-29. Manual Loop Control

(fig. 5-14)

a. The direction finder set uses a servo-driven

resolver functioning as a goniometer instead of

the conventional rotating loop antenna used

in some adf systems. A goniometer generates a

rotating figure-eight loop antenna pattern

identical to that produced by a rotating loop

antenna. The aircraft bearing indicator follows

the goniometer rotor position and indicates the

azimuth or direction in which a loop antenna

would point to if it could rotate. A loop switch

on the control unit enables the operator to position the goniometer and bearing indicator

manually for either manual direction finding or

to check the precision of bearing indication in

adf operating mode. This is accomplished by

observing the precision in which the bearing

indicator pointer returns to its original bearing

indication after the goniometer rotates past a

null position. When manual direction finding

mode is desired, the operator sets the control

unit function switch to LOOP position.

b. In figure 5–14, two phases of 110-CPS signals derived from the receiver 110-CPS oscillator Q22 are applied to LOOP switch S303.

Switch S303 has two positions right or left,

with spring return to its center or grounded

position, In the first position left or right, the

magnitude of the 110-CPS signals are attenuated

by resistors R306 and R307. These two switch

positions are slow speed positions, providing a

slower speed of goniometer rotation than the

second switch position left or right. When

switch S303 is in its center position, the servoarnplifier manual loop control signal path is

grounded, preventing spurious signals from

affecting adf operation. Positioning switch

S303 either right or left applies either phase

1 or phase 2 (180° out-of-phase with phase 1)

to servoamplifier input transformer T18, When

the control unit function switch is set to LOOP

position, switch S1-L grounds terminal 1 of

TM 11-5826-225-35

transformer T18 and the collector of second

resolver servoamplifier Q18. Terminal 2 of

T18 is then used as the servoamplifier input

Phase 1 of the 110-cps signal applied to pushpull resolver servoamplifier Q24 and Q25

causes clockwise rotation (to right) of resolver

B3 functioning as a goniometer, and phase 2

of the 110-CPS signal causes a counterclockwise

rotation (to left). Synchro transmitter B4 and

the aircraft bearing indicator follows resolver

B3.

c. When manual goniometer rotation is desired while operating in adf mode, the control

unit function switch is set to ADF position.

Switch S1–L, operating through the control

unit and receiver autopositioner circuit (para

1–27), removes the ground from the collector

of Q18 (fig. 5–14). Normally in adf operation,

the collector voltage and current path of Q18

is through grounded LOOP switch S303 and

the primary winding of T18. Positioning LOOP

switch S303 either right or left opens the collector circuit and thus disables adf operation.

The resistance of R133 is sufficient to prevent

Q18 from receiving collector voltage while providing a ground return for T18. These circumstances permit manual goniometer rotation in

adf operating mode. All electrical connections

between the control unit and receiver are made

through the receiver mount and airframe

cabling. For resolver servo amplifier circuit

details refer to paragraph 1–18.

1–30. Manual Audio and RF Gain Control

When the direction finder set is operated as

an automatic direction finder (adf), audio gain

is controlled by dual gain potentiometers in the

control unit. The RF gain cannot be varied

manually. In antenna and manual direction

finding modes, RF gain is controlled by a potentiometer ganged to the audio gain potentiometers. Audio gain cannot be varied.

a. Manual Audio Gain Circuit (fig. 5-15).

The receiver audio output from transformer

T20 is applied through connections in the receiver mount and airframe cabling to control

unit function switch S302, which is shown in

ADF position. Variable

R301–B, in conjunction

resistors R301–A and

with resistors R304

Change 1 1-27
TM 11-5826225-35

Figure 1-17.

1-28 Change 5
and R305, forms a bridged-T attenuator which

presents a constant 600-ohm output impedance

to the aircraft interphone system. This impedance value matches the aircraft voice range

filter network. impedance. When function

switch S302 is set to either ANT or LOOP,

the variable resistors are shorted out by contacts 4 on the front and rear wafers of S302-A.

In LOOP operating mode, switch wafer S1-L,

connects capacitor Cl 11 in parallel with terminals 3 and 4 of output transformer T20. This

reduces the audio output level so that sharper

aural nulls may be obtained during manual

direction finding. It should be noted that turning the GAIN control clockwise rotates R301

counterclockwise.

b. Manual RF Gain Control Circuit (fig. 1-

17). In antenna and manual direction finding

mode, only RF gain can be varied manually.

This is accomplished by varying the bias on

two IF amplifier stages and on the push-pull

RF amplifier. An increase in positive bias

voltage decreases gain. When function switch

TM 11-5826-225-25

S302 is set to either ANT or LOOP, +15

volts dc is attenuated by variable resistor

R301-C and applied as bias voltage to transistors Q2, Q4, Q7, and Q8. The network comprising thermistor RT1 and resistor R118

stabilizes bias voltages by temperature compensation. In the LOOP position of switch

S302, resistor R303 decreases RF gain to compensate for the increase in gain caused by

switching out certain signal attenuating networks in the receiver RF stages during loop

operation, thus, RF gain is practically the

same in either antenna or loop operating

modes for the same RF gain control setting.

In adf mode, variable resistor R301-C is bypassed through switch S302 applying + 15-volt

bias \vithout attenuation. It should be noted

that turning the GAIN control clockwise, rotates R301 counterclockwise.

1-31. Receiver Bfo Switching

(fig. 1-18)

The control unit BFO–OFF switch controls

Figure 1-18. Bfo control circuit, schematic diagram.

Change 5 1-29
TM 11-5826-225-25

operation of bfo Q21 by supplying or removing

emitter and base bias voltages. A regulated

source of + 15 volts dc is connected to one side

of BFO–OFF switch S301. Setting the switch

of BFO, applies proper bias voltages to Q21

causing it to oscillate. When the BFO–OFF

switch is set to OFF, bias voltage is removed

and transistor Q21 cannot oscillate. The bfo

is used for tuning to zero beat when receiving

continuous wave (C W) signals. For bfo circuit

functioning, refer to paragraph 1-14.

1-32. Receiver Tuning Meter

(fig. 1-19)

Tuning meter M301 mounted on the control

unit front panel is a dc microammeter requiring 100 microampere of current for full-scale

deflection. The negative side of M301 is

grounded and the positive side is connected to

the cathode of meter rectifier CR10 through a

low-pass filter comprising R40, L15, C117, and

C114. The current flowing through M301 is the

half wave, rectified, positive cycles of signal

present at the output of IF transformer T17.

This current is proportional to the amplitude

of IF amplifier signal and reaches maximum

amplitude when the receiver is tuned to the

RF carrier of a radio station. The receiver is

tuned for maximum tuning meter indication.

Figure 1-19. Remover tuning meter, schematic diagram.

1-30 Change 5
TM 11-5826-225-35

CHAPTER 2

TROUBLESHOOTING

Section 1. GENERAL TROUBLESHOOTING TECHNIQUES

2-1. General

The dirtect support, general support, and

depot maintenance procedures in this manual

supplement the procedures outlined in the

operator’s and organizational maintenance

manual. The systematic troubleshooting procedure, which begins with the operational and

sectionalization checks that can be performed

at an organizational level, is carried to a higher

level in this manual. Sectionalizing, localizing,

and isolating techniques used in the troubleshooting procedures are more advanced.

2-2. Organization of Troubleshooting

a. General. The first step in servicing a malfunctioning direction finder set is to sectionalize

the fault. Sectionalization means tracing the

fault to a unit or circuit. The second step is to

localize the fault. Localization means tracing

the fault to a defective part responsible for the

abnormal condition. Some faults, such as

burned-out resistors, and arcing and shorted

transformers or motors, can often be located

by sight, smell, and hearing. The majority of

fault, however, must be isolated by checking

voltages and resistances.

b, Sectionalization. Listed below is a group

of test arranged to reduce unnecessary work,

and to aid in tracing trouble in a malfunctioning direction finder set, Direction Finder Set

AN/ARN-88 consists of five units; the control

unit the receiver, the mounting, the inverter,

and the loop antenna. The first step is to locate

the unit or units at fault by the following

methods:

(1)

(2)

Visual inspection. The purpose of

visual inspection is to locate faults

without testing or measuring circuit.

Indications on the aircraft healing

indicator and on the control unit

tuning meter or other visual signs

should be observed during all operating modes, and an attempt should

be made to sectionalize the fault to a

particular unit.

0perational tests. Operational tests

frequently indicate the general location of trouble. In many instances, the

tests will help in determining the exact

nature of the fault. The intermediate

preventive maintenance checks and

services chart (TM 11-5826-225-12)

contains a list of operational checks

which helps to sectionalize troubles to

a unit.

c. Localization. After the trouble has been

sectionalized ( b above), the methods listed in

(1) through (3) below will aid in localizing the

trouble to a circuit, stage, or mechanical system in the suspected unit.

(1) Troubleshooting chart. Tuning meter

and bearing indicator indications or

lack of indications and operational

checks provide a systematic method of

localizing trouble to a circuit, stage, or

mechanical system. The trouble symptoms listed in the troubleshooting

charts ( paras 2-5d and 2-9b ) will provide additional information for localizing trouble.

2-1
TM 11-5826-225-35

(2)

(3)

Signal substitution. Signal substitution procedures for the receiver (para

2-6) enable the repairman to localize

a trouble quickly to a receiver circuit

or stage. An RF signal generator,

audio oscillator, and oscilloscope are

units of test equipment (para 2–3e)

that may be used in signal substitution procedures. Observe the caution

notice in paragraph 2–6a arid follow

the signal substitution procedures

(para 2–6) closely so that damage to

transistors may be avoided.

Stage-gain charts, The receiver stagegain charts (para 2–7) will help locate difficult troubles that produce

weak signals and should be used when

performing the signal substitution

procedures.

d. Isolation. After the trouble has been localized (c above), the methods in (1) through

(5) below will help in isolating the trouble

to a defective circuit element.

(1)

(2)

(3)

2-2

Waveform analysis. Voltage readings

taken in some cases are difficult if

not impossible to analyze because

these voltages vary with circuit conditions (equipment operation). For

these circuits, waveforms must be

taken and compared with the waveforms provided.

Voltage measurements. This equipment is transistorized. When measurin voltages, use tape or sleeving (spaghetti) to insulate the entire test

prod, except for the extreme tip. A

momentary short circuit can ruin the

transistor. For these voltage measurements, use Multitester ME-26/U

(vtvm) or the equivalent.

Resistance measurements. TO avoid

transistor damage, make resistance

measurements in this equipment only

as necessary.

Caution: Before using an ohmmeter

to test in transistor circuits, check the

open circuit voltage across the ohmmeter test leads. Do not use the ohmmeter if the open circuit voltage exChange 4

TP1 ,

(4)

ceeds 1.5 volt. Since the Rx1 range

normally connects the ohmmeter internal battery directly across the test

leads, the excessively high current (50

ma or more) may ruin some transistors in the circuit. For a safe current that will not damage transistors,

use the Rx100 range of Multi meter

TS-352/U.

Test points. All wiring in this equipment iS from point-to-point. The wiring and component junction connections are supported by insulated

standoff terminal studs. Any of these

terminals may be used as a test point

as required. No test jacks are provided. The terminal studs used for

testing and troubleshooting in the receiver are shown on the main schematic diagram (fig. 5–10 or 5-10.1) as

TP2, ect .

(5)

(6)

Intermittent troubles. In all of these

tests, the possibility of intermittent

troubles should not be overlooked. If

present, this type of trouble may

often be made to appear by tapping

or jarring the equipment. Make a

visual inspection of the wiring and

connections.

Resistor and capacitor color code diagrams. Resistor and capacitor color

code diagrams (figs. 4-11 and 5-1)

are provided to aid maintenance personnel in determining the value, voltage rating, and tolerance of capacitors

and resistors.

2–3. Test Equipment Required

The following chart lists test equipment required for troubleshooting Direction Finder

Sot AN/ARN-83 and the associated technical

manuals.

Caution: The receiver and inverter circuits

are transistorized. Use all precautions to avoid

transistor damage.

a. Never connect test equipment (other than

multimeter and vtvm’s) outputs directly to a

transistor circuit; use a coupling capacitor.
TM 11-5826-225-35

because the output voltage of a supply having

poor regulation, may exceed the maximum

voltage rating of the transistors in the equip

ment being tested. A battery eliminator with

poor ac filtering will create a false indication

of poor filtering in the equipment being tested.

d. The direction tinder set must be turned

off before switching the battery eliminator on

or off, The transient voltages developed by

switching the battery eliminator on and off,

may exceed the “punch-through” rating of

transistor. Also, make certain that either a

600-ohm dummy load or a normal load (such

as a headset) is connected to the direction

finder set audio output before applying power.

Section Il. TROUBLESHOOTING RADIO RECEIVER R–1391/ARN–83

2-4. Test Setup (2)

All bench tests of the receiver, require connections to a 27.5-volt dc power source; Test

Set, Direction Finder Set AN/ARM-93; and (3)

various other types of test equipment depending on the particular test. To prepare the receiver for tests, loosen the dust cover retaining screws (fig. 2–1) and slide the receiver

out of its dust cover. Remove the gear train

cover and the RF shield. Make the test setup (4)

as described below.

a. Confections. (5)

(1) Connect the receiver and test set as

shown in figure 2-2, Use the pendant

cable, the sense antenna adapter cable,

and cable W3 from the test set.

Connect the output meter to the

AUDIO OUT terminals on the test

set.

Connect the R.F. OUTPUT X-MULT

output connector of the signal generator to the SIGNAL GENERATOR

connector on the test set. Use cable

W2 of the AN/ARM-93.

Set the switch on the sense antenna

adapter to 150PF.

After making certain the test set DC

POWER switch is off, connect the

dc power source to the test set. If

the aircraft dc source is not available, use a battery eliminator capable

Change 4 2-3
TM 11-5826-225-35

Figure 2-1. Receiver, dust cover retaining screws locotion,

of supplying 27.5 volts dc at 3 amperes.

b. Test Equipment. The test set has circuitry for

simulating the loop and sense antennas and provisions

for rotating the apparent loop antenna magnetic field

360° in either direction. A bearing indicator and phone

jack are also provided. The test setup shown in figure

2-2 is a preliminary troubleshooting test setup. Test

connections will vary from test to test.

2-5. Localizing Troubles

a. General. The troubleshooting chart (d below)

contains procedures for localizing troubles to the af, IF,

and RF sections of the receiver, and for localizing troubles to a stage within the various

section. Parts location is indicated in figures

2-3 through 2-16.1. Depending on the nature of

the operational trouble symptom, one or more

o f the localizin g procedure s will

be necessary. When use of the proce -

dures results in localization of trouble to a

2-4 Change 3
TM 11-5826-225-35

Figure 2–2. Receiver test setup.

particular stage, use the techniques outlined

in paragraphs 2–6 through 2–8 to isolate the

trouble to a particular part.

b. Use of Chart. The troubleshooting chart

in this manual supplements the operational

checks and troubleshooting instructions in- (2)

eluded in TM 11–5826-225-12. If operational

checks in TM 11–5826-225–12 have resulted in

reference to a particular item of the chart,

start with this referenced item.

c. Conditions for Tests. All checks outlined

in the chart are to be conducted with the receiver connected to Test Set, Direction Finder

Set AN/ARM–93 as indicated in figure 2–2.

Unless otherwise indicated in the chart, set

the control unit, test set, and signal generator (3)

controls as follows:

(1) Test set. Set the test set controls as

follows:

Contion Position

RECEIVER–

CONTROL ________ RECEIVER

GONIO DRIVE . ..__. OFF

DC POWER -------- ON

Control unit. Set the control unit controls as follows:

Control Position

BFO–OFF _ . . . . . . . . . . OFF

Function switch . . . . ANT

Range switch -------- 190-400

TUNE ------------ 200 kc

GAIN . . . . . . . . . . . . ..- Maximum

clockwise

position

Signal generator. Tune the signal generator to 200 kc and set the controls

for an RF output signal of 50 microvolt, modulated 30 percent at 400 cps.

2–5
TM 11-5826-225-35

Figure 2-3.

2-6
TM 11-5826-225-35

Figure 2-4. Audio frequency amplifier assembly.

Change 5 2-7
TM 11-5826-225-35

Figure 2-5. Bfo subassembly.

2-8
TM 11-5826-225-35

Figure 2-6. Power supply and servo compartment, right side view.

Change 5 2-9
TM 11-S826-225-35

Figure 2-7. Power supply and servo

2-10 Change 1
TM 11-5826-225-35

Figure 2-8. Receiver, left side view with gear train

cover and RF shield removed.

2-11
TM 11-5826-225-35

Figure 2-9. First RF amplifier subassembly.

2-12
TM 11-5826-225-35

Figure 2-9.1 First RF amplifier subassembly,

front view (MCN 1084 and above).

Change 1 2-12.1

TM 11-5826-225-35

Figure 2-10. Second RF amplifier and balanced

modulator subassembly.

Change 1 2-13
TM 11-5826-225-35

Figure 2–10.1 Second RF amplifier and balanced

modulator subassembly (MCN 1084 and above).

2-14 Change 1
TM 11-5826-225-35

Figure 2-11. Push-pull RF amplifier

subassembly, front view.

Change 1 2-14.1
TM 11-5826-225-35

Figure 2-11.1 Push-pull RF amplifier

subassembly, front view (MCN 1084 and above).

2-14.2 Change 1
TM 11-5826-225-35

Figure 2-12. Push-pull RF amplifier

subassembly, side view.

Change 1 2-15
TM 11-5826-225-35

Figure 2-12.1 Push-pull RF amplifier subassembly,

side view (MCN 1084 and above).

2-16 Change 1
TM 11-5826-225-35

Figure 2-18. Mixer assembly.

Change 1 2-16-1
TM 11-5826-225-35

Figure 2-13.1 Mixer assembly, front view

(MCN 1084 and above).

2-16.2 Change 1
TM 11-5826-225-35

Figure 2-14. IF amplifier subassembly

front view.

Change 1 2-17
Figure 2-14.1

2-18 Change 1
TM 11-5826-225-35

Figure 2-15. IF amplifier subassembly,

rear view.

Figure 2-15.1 IF amplifier subassembly,

rear view (MCN 1084 and above).

Change 1 2-18.1
TM 11-5826-225-35

Figure 2-16. Local oscillator subassembly.

2-18.2 Change 1
TM 11-5826-225-35

Figure 2-16.1 Local oscillator asssmbly, rear view

(MCN 1084 and above).

Change 1 2-18.3


TM 11-5826-225-35

d. Receiver Troubleshooting Chart.

1

2

3

4

5

6

7

R

Indication

No audio output but control unit tuning meter

indicates signal

strength.

With control unit BFOOFF switch to BFO, no

beat notes can be heard

in headset connected to

PHONE jack on test

set.

Audio output is normal

but control unit tuning

meter is inoperative.

No audio output or tuning

meter indication.

Audio output missing on

one or more frequent:

ranges,

Signal output varies

First IF amplifier Q7

Weak audio output on on

or more frequency

ranges.

Probable trouble

Defective audio output stage

First or second audio amplifier stage defective.

Audio detector defective ----

Network Z1 defective _____

Fifth IF amplifier defective.

Bfo defective ---. -.. __..._

Meter rectifier defective ___

Regulated power supply defective.

First, second, third, or

fourth IF amplifier stage

defective.

Mixer stage _______________

Local oscillator stage defective.

Switch wafer S1-J dirty---

Oscillator out of alignment .

Automatic gain control circuit defective.

Sense antenna input circuit

or push-pull RF amplifier.

Procedure

Remove power and check transistor Q14 (fig.

2-3) with Transistor Tester TS–1836/U.

Make voltage measurements on audio output

stage (fig. 2–17 ).

Make continuity tests on audio output transformer T20 (para 2-9a).

Remove power and check transistors Q12 and

Q13 (fig. 2-4).

Make voltage measurements on first and second audio amplifier stages (fig. 2-17).

Using vtvm, check voltage output from cathode of audio detector CR1 (fig. 2-14 or 2-14.1)

Check continuity of Z1.

Check transistor Qll (fig. 2-8),

Make voltage measurements (fig. 2-17).

Check transistor Q21 (fig. 2-3).

Make voltage measurements (fig. 2-17 ).

Using vtvm, check dc output voltage of diode CR1O (fig. 2-14 or 2-14.1) ,

See item 9

Check transistors Q7, Q8, Q9, and Q1O (fig.

2-8).

Make voltage measurements (fig. 2-17).

Make continuity checks on IF transformers

T14, T15, T16, and T17 (para 2-9a).

Perform signal substitution tests (para 2-6).

Make stage gain measurements (para 2-7).

Check mixer Q5 (fig. 2-8).

Make voltage measurements (fig. 2-17).

Check continuity of T13 (para 2-9a).

Check oscillator Q6 (fig, 2-8).

Make voltage measurements (fig. 2-17).

Make continuity checks on oscillator coils

(para 2-9a).

Clean switch contacts (fig. 2-8).

Align oscillator (para 3-13).

Using transistor tester, check agc amplifiers Q15 and Q16 (fig. 2-3).

Using vtvm, check dc output voltage of agc

rectifier CR3 (fig. 2-14 or 2-14.1 )

Make voltage measurements on agc amplifiers Q15 and Q16 (fig. 2-3).

Check transistors Q2 and Q4 (fig. 2-8).

Make voltage measurements (fig. 2-17).

Change 1 2-19
TM 11-5826-225-35

Item

9

10

11

12

13

14

15

2-20

indication

Regulated power supply

defective.

Noise heard in headset

connected in PHONE

jack on test set when

receiver switches frequency. ranges.

Receiver does not switch

frequency ranges o r

functions.

Receiver does not tune to

to a radio station.

Tuning servo does not

hold station frequency,

Tuning servo hunts

When test set LOOP SIM

for 90-degree indication

from indicated bearing

BEARING INDICATOR rotates hut does

not reach a null.

Push-pull RF amplifier and

mixer coupling network

out of alignment.

Sense antenna input network out of alignment.

Switch wafers not making

contact.

Receiver muting circuit

switch wafer S1-M no t

closing dc voltage circuit

to motor B2.

Servo amplifier Q26, Q27,

Q28, or Q29 defective.

Capacitor C74 coupled to

control winding of tuning

servo motor.

Tachometer feedback variable resistor R111 out of

adjustment.

Loss of 110-cps reference

phase voltage on reference winding o f servo

motor B5 because of defective 110-cps amplifier

stage.

Procedure

Align network (para 3-14).

Align network (para 3-14),

Check continuity through contacts of switch

wafers S1-C, S1–0, S1–N, and S1–R (fig.

2-8)

Check transistors Q30 and Q3l (fig. 2-6).

Make voltage measurements (fig. 2-17).

While receiver switches frequency ranges,

check positive dc voltage, on base of agc

amplifier Q16 (fig. 2-3). Base voltage

should rise sharply. If not, replace diode

CR5.

While receiver switches frequency ranges,

check for presence of +27.5 volts on contacts of rear switch wafer S1–M (fig. 2-8),

Clean switch if necessary.

Check transistors (fig. 2-6).

Make voltage measurements ( fig. 2-17).

Check capacitor (fig. 2-6)

Adjust Rlll (para 3-10).

Note. Unless otherwise indicated for items 15 through,

18, set control unit and test equipment controls a s

follows :

(1) On tbe, test set, place DC POWER to ON, GONIO

DRIVE to ON. and loop simulator control for an

indication on LOOP SIMULATOR 90 degrees more.

than indicated on HEARING INDICATOR.

(2) Tune signal generator to 200 kc with an RF

Output of 50 microvolts unmodulated.

(.3) On the control unit, set function switch to ANT,

range switch to 190-400, GAIN to maximum clockwise position, BFO-OFF to BFO, and TUNE for

zero-beat on 200 kc. After zero-beat, set BOF-OFF

to OFF and function switch to ADF.

Using oscilloscope, check for waveforms on

base and collector of Q23 (fig. 2-7). If

present, compare waveforms taken with

those shown in figure 2-18.

Make voltage measurements on stage of Q23

(fig. 2-17).

Using transistor tester, check Q23.
TM 11-5826-225-35

Item

16

17

Indication Probable trouble

Erratic operation of bear.

ing indicator.

I

110-CPS oscillator stage defective.

Push-pull resolver servo amplifier stage.

Balanced modulator balance

adjustment variable resistor R1O.

Loss of 110 cps on balanced

modulator by reason of

switch wafer S1–D not

making contact.

First or second RF amplifier stage defective.

Power supply variable resistor R131 out of adjustment (provides base and

emitter bias voltages for

first resolver servo amplifier Q17).

110-cps oscillator or 110-CPS

amplifier defective.

Push-pull resolver servo amplifier stage.

First or second resolver

servo amplifier stage defective.

Synchronous filter stage defective.

First agc amplifier defective

(emitter follower function

drives synchronous filter).

Will not reach aural null Voltage regulator filter ca-

(sound will not cut off). pacitor defective.

Voltage regulator zener diode CR4 or CR1l, oscillating.

Procedure

Check continuity of reference winding of B5.

Using transistor tester, check transistor Q22

(fig. 2-6).

With oscilloscope, check waveforms on base

and collector of Q22 (fig. 2–18).

Make voltage measurements (fig. 2-17).

Check continuity of coil L32 (para 2-9a).

Check transistors Q24 and Q25 (fig. 2-6).

Make voltage measurements on Q24 and Q25

(fig. 2-17).

Adjust R10 (para 3-19).

Check continuity through switch contacts of

S1–4 (fig. 2–8). Clean contacts if corroded.

Check transistors Q1 and Q3 (fig. 2-8).

Make voltage measurements (fig. 2-17).

Adjust R131 (fig. 2-8 and para 3-20).

See item 15.

See item 15.

Check transistors Q17 and Q18 (fig. 2-8).

Make voltage measurements (fig. 2-17).

Check transistors Q19 and Q20 (fig. 2-3).

Make voltage measurements (fig. 2-17).

Using oscilloscope, check 110-CPS waveforms

on bases of Q19 and Q20. Compare with

waveforms in figure 2–18.

Check transistor Q16 (fig. 2-3).

Make voltage measurements (fig. 2-17).

Using oscilloscope, check for presence of 110-

cps on base and emitter of Q16.

Note. Before continuing with items 17 and 18, set

control unit function switch to LOOP. Modulate signal

generator output signal with approximately 30 percen t

modulation. Using LOOP switch, rotate bearing indicator to aural null in headset.

Check filter capacitors.

Using oscilloscope or ac range of vtvm, check

for ac ripple on collector of

Q30 and base of Q31 (fig. 2-6).

Change 1 2-21
TM 11-5826-225-35

Item Indication I Probable trouble

Control unit LOOP switch

rotates bearing indicator pointer in one direction only.

Audio amplifier Q12, Q13, or

Q14 defective.

Loss of 110-CPS reference

phase voltage on resolver

servo motor B5.

2-6. Signal Substitution

a. General. Signal substitution procedures

help to localize trouble to a stage in the receiver. An externally generated signal is substituted for the signal normally present in each

stage. The test equipment required for the

tests in b through d below is listed in paragraph 2-3e. In the following tests, ground one

side of the audio oscillator or signal generator

to the receiver chassis and conned the output

lead to the receiver test point indicated. When

performing these tests, use the receiver main

schematic diagram (fig. 5-10 or 5-10.1.) in

conjunction with the parts location

illustrations referenced in the following procedures.

Caution: All circuits in the receiver are

transistorized. To avoid transistor damage, use

tape or sleeving to cover the test leads except

for the extreme end required for testing,

b. Audiofrequency Tests. Start these tests

at the output of the last audio amplifier stage

and work back toward the first stage (figs.

2–3 and 2-4 ). Turn variable resistor R82

fully clockwise.

(1)

(2)

(3)

Connect the receiver to Test Set, Direction Finder Set AN/ARM–93 as

shown in figure 2–2, but do not connect RF Signal Generator AN/URM–

25. Set the test set and control unit

controls as indicated in paragraph

2-5c. The range switch and TUNE

control may be set in any position.

Procedure

Check transistors (fig. 2–3).

See item 15.

(4)

(5)

(6)

(7)

Listen for audio output signal in

headset. If. no signal is heard, check

audio output transformer T20 and

capacitor C78.

Set audio oscillator output signal level

to 850 millivolts and apply signal to

the collector of Q13. Audio output

from the headset should be as loud as

obtained in (4) above. If no sound

is heard or output is low, check transistor Q14 and associated base signal

input circuitry.

Set audio oscillator output signal to

33 millivolts and apply signal to the

base of Q13. Sound output should be

equal to that obtained in (4). If no

sound is heard or sound level is weak,

check transistor Q 13 and associated

circuit components.

Adjust audio oscillator for an output

of 42 millivolts and apply signal to

the base of transistor Q12. Sound output in headset should he equal to that

obtained in (4). If not, check transistor Q12 and associated circuit components.

Note. After making the above tests, adjust

the variable resistor R82 in accordance with

the instructions in paragraph 3-17.

c. Intermediate Frequency Tests. Start the

tests at the output of the last IF amplifier

stage and work back toward the first IF stage

(figs. 2-8 and 2-15 or 2-15.1). Turn variable

Set Audio Oscillator TS-382/U to pro- resistor R90 (fig. 2-8) fully clockwise.

duce an audio output signal of 400 (1) Use the test setup described in paracycles at 5 volts rms. graph 2–6b (1).

Using a 10-microfarad capacitor in (2) Set RF Signal Generator AN/URM--

series with the audio oscillator out- 25 for a 142.5-kc output signal modput lead, connect lead to the collector ulated 30 percent at 400 cps. Adjust

of audio amplifier Q14. output signal level to 50 millivolts.

2-22 Change 1
(3)

(4)

(5)

(6)

(7)

(8)

(9)

Using the 50-ohm probe, apply signal

to test point TP2 (collector of Q11

and network Z1).

Listen for audio output signal in

headset. If no sound is heard, check

network Z1, audio detector CR1, audio

limiter CR2, and associated circuit

components.

Apply signal generator RF signal to

the base of transistor Q11. Audio output signal level should increase. If

no sound is heard or sound is low,

check transistor Q11 and associated

circuit components.

Apply signal to the base of Q10.

Audio output signal should increase.

If not, check transistor Q10, IF transformer T17, coupling capacitor C53,

and associated parts.

Adjust signal generator for an output level of 15 millivolts, Apply signal to the base of Q9. If no sound

is heard or sound output is low, check

transistor Q9, IF transformer T16,

coupling capacitor C108, and associated circuit components.

Using a jumper wire, ground agc test

point TP3. Adjust signal generator

output signal to 250 microvolt and

apply signal to base of Q8. If no

sound is heard in headset or output

is low, check transistor Q8, IF transformer T15, coupling capacitor C51,

and associated circuit components.

Adjust signal generator for an output level of 10 microvolt and apply

signal to base of transistor Q7. If no

sound. is heard or sound is low, check

transistor Q7, IF transformer T14,

coupling capacitor C48, and associated circuit components.

Adjust signal generator output level

to 100 microvolt and apply signal to

the collector of Q5 through the 50-

ohm probe. If audio output signal is

low or absent, check IF transformer

T13, variable resistor R90, coupling

capacitor C110, and associated components.

TM 11-5826-225-35

Note. After making the above tests, adjust

variable resistor R90 in accordance with the

instructions in paragraph 3–17. Remove

ground from agc testpoint TP3.

d. Radio frequency Tests. Start the radiofrequency tests at the mixer stage and work

back toward the antenna inputs.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

Unless otherwise indicated, use the

test setup described in paragraph 2–

6b(l).

Turn variable resistor R90 (fig. 2-7)

fully clockwise. Ground age testpoint

TP3.

Adjust signal generator for a 200-kc

unmodulated output signal at a level

of approximately 5 microvolts. Using

50-ohm probe, apply signal to testpoint TP4 connected to junction of

capacitor C29 and contact number 3

of front switch wafer S1-I (figs. 2–8

and 2–13 or 2-13.1).

Set control unit BFO–OFF switch to

BFO and function switch to ANT.

Adjust TUNE control for zero beat in

headset then turn BFO–OFF switch

to OFF.

Adjust signal generator controls for

an output signal modulated 30 percent at 400 cps. If no sound is heard,

check mixer Q5 and associated circuit

components.

Using 50-ohm probe in series with

signal generator output lead, apply

200-kc RF signal to the base of RF

amplifier 4 (figs. 2-8 and 2-11

or 2-11.1.

If no sound is heard or sound is low,

check transistor Q4 and stage circuit

components. Check condition of

switch contacts on wafers S1–P and

S1–1. Check alignment of RF amplifier and mixer coupling network used

on the 190- to 400-kc range (para

3-14), Check RF transformers T107

and T10.

Apply signal to the base of transistor

Q2. If no sound is hoard in headset,

check transistor Q2 and associated

circuit components. Check condition

of switch contacts on wafer S1–P.

Change 1 2-23
TM 11-5826-225-35

(9) Set control unit and signal generator

controls for using RF test signals on

the 400- to 850-kc and 850- to 1750-kc

ranges. For each test signal, set control unit BFO-OFF switch to BFO

and tune for zero beat. Then set BFO–

OFF switch to OFF. Using the 50-

ohm probe, apply modulated signal

to the base of Q4. If no sound is heard

or sound output is weak on either frequency range, check the alignment of

tuned circuit (para 3–14). Check RF

transformers.

(10) Use the test setup shown in figure

2–2 and described in paragraph 2–

6b(1). Connect RF signal generator

to input of test set. Do not use 50-

ohm probe. Set signal generator for a

200-kc unmodulated output signal at

a level of 50 microvolt.

(11) Set control unit BFO-OFF switch to

BFO and tune unit to 200 kc. Adjust

signal generator for zero beat and

then set BFO–OFF switch to OFF.

Modulate signal generator 30 percent

at 400 cps.

(12) Listen for sound in headset. If sound

is weak or missing, check condition of

switch contacts on wafers S1-R,

S1-N, S1-0, and S1–C. Check RF

transformer T104 and alignment.

(13) Set control unit and signal generator

controls for using test signals on the

400- to 850-kc and 850- to 1750-kc

ranges. For each test signal, set BFO–

OFF to BFO and tune for zero beat.

Then set BFO–OFF to OFF and modulate signal generator output signal.

(14) Listen for sound in headset. If low

or missing on any frequency range,

check alignment (para 3-14) and RF

transformer T105 or T106.

(15) For the following radiofrequency

tests, set control unit function switch

to LOOP, GAIN control fully clockwise, and range switch to 190- to 400-

kc range. Tune to 200 kc.

(16) Using 50-ohm probe, connect signal

generator output to the base of second RF amplifier Q3 (figs. 2-8

and 2-10 or 2-10.1).

. Set signal generator for an unmodulated 200-kc output signal at a

level of 50 microvolt.

(17) Set control unit BFO-OFF switch to

BFO and tune for zero beat. Then set

FIFO-OFF switch to OFF. Modulate

signal generator 30 percent at 400

cps.

(18) Listen for audio in headset. If low or

missing, check transistor Q3 and associated circuit components.

(19) Using 50-ohm probe, apply signal

generator output signal to the base

of first RF amplifier Q1 (figs. 2–8 and 2-9

or 2-9.1)Set signal generator for an output of 100 microvolt.

(20) Listen for audio in headset. If low or

missing, check transistor Q1 and associated circuit components. Check condition of switch contacts on wafers

S1–D and S1–E. Check coils and associated components in 90-degree phaseshift network between switch wafers

S1-D and S1-E.

(21) Setting control unit and signal generator controls accordingly, listen for

audio on the other two frequency

ranges. If weak or missing, check

switches and 90-degree phase-shift

network.

(22) Connect signal generator to input of

test set (fig. 2-2). Do not use 50-ohm

probe. Tune signal generator for a

200-kc unmodulated output signal at

a level of 100 microvolt.

(23) Set test set GONIO DRIVE switch to

OFF. Adjust loop simulator control

for an indication on the LOOP SIMULATOR that is 90 degrees more than

the indication on the test set BEARING INDICATOR.

(24) Set control unit. function switch to

ANT. Set BFO–OFF switch to BFO

and tune signal generator for zero

beat in headset. Set BFO-OFF to

OFF and set function switch to ADF

Modulate signal generator output,

signal 30 percent at 400 cps.

2-24 Change 1
(25)

(26)

(27)

If audio output is low or missing,

check condition of switch contacts on

wafers S1–F and S1–G. Check RF

transformer T1 and associated circuit. Check RF resolver B3.

Setting control unit and signal generator controls accordingly, listen for

audio on the other two frequency

ranges. If weak or missing, check RF

transformer T2 or T3, and resolver

B3.

Remove ground from agc test point

TP3. Adjust variable resistor R90 as

outlined in paragraph 3–17.

2-7. Stage-Gain Measurements

Use the techniques given in a through j below when either the receiver audio is abnormally low, or the bearing indicator has a slow

response.

a General Instructions. Connect the receiver

and control unit to Test Set, Direction Finder

Set AN/ARM-93 as shown in figure 2-2 and

outlined in paragraph 2–6b (1). Unless otherwise instructed, do not connect RF Signal

Generator AN/URM-25 to the test set. In

addition to the test set and RF signal generator, Multitester ME–26/U and Audio Oscillator TS–382/U are also required for these tests.

Verify operation of the test equipment by performing the steps outlined in the operation

and maintenance sections of the technical

manuals covering the test, equipment being

used. Record the output level of the signal generator for each test and determine the gain

of each stage. Stage gain is computed by dividing the input signal voltage applied to the

following stage by the input voltage applied

to the stage under test. Some transistor stages

in various circuits of the receiver contribute

little if any gain and in some instances a loss

in gain. These stage gains or losses are shown

in charts included in the following stage-gain

measurement procedures. Use the main schematic diagram (fig. 5–10 or 5-10.1)

in conjunction with

the parts location illustrations referred to.

b. Audio Amplifier Stages (figs. 2-3 a n d

2-4). Using a 10-microfarad coupling capacitor, connect the audio oscillator output between

TM 11-5826-225-35

chassis ground and points indicated in the Test

connection column of the following chart. Adjust signal output put to 400 cps at a level to obtain the voltage indication specified in the

Input column. Set vtvm for measuring ac voltages in the appropriate voltage range and

Connect ac probe of vtvm between the points

indicated and chassis ground. Compare the

indications obtained on the vtvm with those

listed in the output column, If gain differs

abnormally from that listed in the chart, use

further isolating techniques (para 2–8) to determine the defective component within the

stage.

Note. Turn variable resistor R82 fully clockwise.

After making gain tests, adjust R82 (para 3-17).

Set vtvm for measuring dc voltages from 0 to

5 volts. Connect positive test lead to the cathode

of audio detector CR1 and negative test lead

to the chassis. Turn variable resistor R90 fully

clockwise. Using a jumper wire, ground agc

testpoint TP3. Adjust RF signal generator for

a 142.5-kc output signal, modulated 30 percent

at 400 cps. Set output level to approximately

2.5 volts. Using the 50-ohm probe, connect

output signal to the junction connection of network Z1 and the collector of fifth IF amplifier

Q11 (labeled testpoint TP2 in fig. 5–10 or

5-10.1). Adjust output level of signal generator until vtvm

indicates 5 volts dc. For this reference voltage

level the signal generator RF output should

not exceed 2.1 volts rms. When performing the

stage gain tests in the following chart, start

wit h the last IF amplifier stage and work hack

toward the mixer stage. Connect signal generator 50-ohm probe between chassis ground

and points indicated in the Test connection column. For each stage-gain test, adjust signal

generator output to the voltage specified in the

Change 1 2-25
figs. 2-8

para 3-17

TM 11-5826-225-35

Input column. These voltages in the Input

column are the signal voltage required to obtain an indication of 5 volts dc on the vtvm. If

the voltage differ abnormally, check the IF

transformers and if necessary, use further

isolating techniques (para 2–8) to determine (c)

the defective component.

agc testpoint TP3 and turn variable resistor

R90 fully clockwise. Set vtvm for measuring

dc voltages from O to 5 volts. Connect positive

test lead to cathode of audio detector CR1 (fig. 2-14 o r

2-14.1) and negative test lead to receiver chassis.

Set test set and control unit controls as outlined in paragraph 2–6b(1). Set RF signal

generator output signal to 142.5 kc modulated

30 percent at 400 cps. Adjust output level to 6

or 7 microvolt and apply signal to the base of

first IF amplifier Q7 (fig. 2–8). Then adjust

output signal until vtvm indicates 5 volts dc.

The signal generator output signal required to

produce this de voltage level should be in the

range of 6.5 to 7 microvolt. Record this reference level for use in the following tests. Remove

signal generator and vtvm connections.

(1) Gain of mixer at IF frequency.

(a) With signal generator set as shown

above, use the 50-ohm probe and

apply 142.5-kc RF signal to the

junction of C29 and contact 3 of

front switch wafer S1–1 labeled

TP4 in figure 5-10 or 5-10.1.

(b) Set control unit range switch to the

190- to 400-kc range and tune to

200 kc. Set BFO–OFF switch to

BFO and adjust signal generator

for zero beat. Then set BFO--OFF

switch to OFF

Connect vtvm to cathode of audio

detector CR1. Ground agc testpoint

TP3.

Adjust signal generator output level

to produce an indication of 5 volts

dc on the vtvm. Record the signal

generator output voltage required

to produce the vtvm reading of 5

volts dc .

Determine mixer gain by dividing

the signal generator voltage applied

to the base of Q7, to produce 5 volts

dc on the vtvm as in d above, by the

value obtained in (d) above.

Typical mixer gain values at various

frequencies are listed in the following chart. Repeat the above procedures for the remaining frequencies

listed in the Frequency column. If

mixer gain differs appreciably from

the chart, use further isolating

techniques (para 2–8) to isolate the

defective component. After these

tests, remove the agc ground connection and adjust R90 (para 3–17).

(2) Gain of mixer at RF frequencies.

(a) Turn variable resistor R90 fully

clockwise. Ground test point TP--3.

(b) Set RF signal generator for a 200-

kc output signal at a level of 6 or 7

microvolt. Using 50-ohm probe,

apply signal to the junction of C29

and contact 3 of front switch wafer

S1-I labeled TP-4 in figure 5-10

or 5-10.1 .

2-26 Change 1
(c)

(d)

Repeat paragraph d(l) (b) through

(e) above.

Typical mixer gain values at various radio frequencies are listed in

the following chart. If mixer gain

differs appreciably from the chart,

check the alignment of mixer stage

and if necessary, use further isolating techniques to determine the defective component (para 2-8). After

making these tests, remove agc

ground and adjust R90 (para 3–17 ).

(1)

(2)

(3)

(4)

(5)

Ground IF amplifier agc test point

TP-3.

Set control unit function switch to

LOOP, range switch to 190- to 400-

kc range, BFO-OFF switch to BFO,

and GAIN control fully clockwise.

Tune to 200 kc.

Connect signal generator to input of

test set. Tune to 200 kc and adjust

output to 100 microvolt.

Tune control unit for zero heat and

then set BFO-OFF switch to OFF,

Set vtvm for measuring O to 5 volts

dc and connect vtvm to the cathode of

audio detector CRl (fig. 2-14 or 2-14.1).

(6)

(’i)

(8)

Set test set LOOP SIMULATOR dial

90 degrees from that indicated on

BEARING INDICATOR or for maximum indication on vtvm. Set GONI

DRIVE switch to OFF.

Adjust variable resistor R90 (fig.

2–8) for an indication of 5 volts dc on

vtvm,

Remove signal generator

set and apply signal to the

from test

base of RF

(9)

(11)

(11)

(12)

TM 11-5826-225-35

amplifier Q4 through the 50-ohm

probe (fig. 2–8).

Set control unit function switch to

ANT and BFO–OFF switch to BFO.

Tune for zero beat on 200 kc and then

set BFO–OFF switch to OFF.

Adjust signal generator output signal

to produce an indication of 5 volts dc

on vtvm. Record this value of signal.

Connect signal generator output

through 50-ohm probe to test point

TP-4.

Adjust signal generator output to produce an indication of 5 volts dc on

vtvm. Divide this signal generator

output level by the signal obtained in

step (10). A typical gain at 200 kc is

32. Repeat (2) through (12) above

for each frequency listed in the following chart, If gain differs from that

listed in that chart, check the alignment (para 3-14) and, if necessary,

use further isolating techniques to determine the trouble (para 2-8).

f. Gain of Sense Antenna Input Circiut.

(1)

(2)

(3)

(4)

Repeat e (1) through (7), Then set

control unit function switch to ANT.

Tune signal generator for maximum

indication of vtvm, Note the output

signal required to obtain 5 volts dc on

.

vtvm.

Divide the signal generator output

signal determined in paragraph e (10)

by the value obtained in (2) above, A

typical gain figure at 200 kc is 0.05.

Repeat (1) through (3) above for the

remaining frequencies listed in the

following chart. If gain differs appreChange 1 2-27
TM 11-5826-225-35

ciably from that listed in the chart,

check the alignment of sense antenna

input circuit. After these tests, adjust

R90 (para 3-17).

(1)

(2)

(3)

(4)

( 5 )

2-28

Repeat e (1) through (7).

Listing 50-ohm probe, apply signal

generator output signal to the base of

transistor Q4 (fig. 2–8).

Adjust output of signal generator for

an indication of 5 volts dc on vtvm.

Record the signal generator required

for this dc voltage level.

Using 50-ohm probe, connect signal

generator output to the base of transistor Q3 (fig. 2–8). Adjust output of

signal generator to obtain 5 volts dc

on vtvm.

Divide the signal generator output

signal determined in (3) above by the

value obtained in (4) shove, A typical

gain value for a freqency of 200 k c

is 0.73. Repeat (1) through (4) above

at the frequencies listed in the chart

below. If gain differs appreciably than

listed in the chart, use further isolating techniques (para 2-8) to determine the trouble.

h. Gain of First RF Amplifier and PhaseShift Network.

(1)

(2)

(3)

(`4)

Repeat e (1) through (7).

Using 50-ohm probe, apply signal generator output to the base of Q3 (fig.

2-8). Adjust output signal for a 5-

volt dc indication on the vtvm. Record output signal of signal generator.

Using 50-ohm probe, connect signal

generator to the base of Q1 (fig. 2–8).

Adjust output signal for a reading of

5 volts dc on vtvm.

Divide value recorded in (2) above

by the value obtained in (3) above,

At a frequency of 200 kc, a typical

gain figure is 4.6. Repeat (1) through

(3) above for the remaining frequencies listed in the following chart. If

gain figures differ appreciably, check

transistor Q1 and associated circuit

components. If necessary, use further

isolating techniques to locate the defective component (para 2-8).

(1)
para 2-9a

fig. 2-17

para 2-9a

para 2-6

para 2-7

2-17

(4)

(5)

Adjust signal generator output level

for 5 volts dc on vtvm. Divide signal

level recorded in (2) above by the

present output of signal generator.

The gain at 200 kc should be approximately 0.008.

Repeat (1) through (4) above for the

remaining frequencies listed in the

following chart. If gain differs appreciably, check resolver and loop antenna input circuit.

(1)

(2)

(3)

(4)

(5)

Set control unit function switch to

ANT, BFO–OFF switch to BFO, range

switch to 190- to 400-kc range, and

GAIN control fully clockwise. Tune

to 300 kc.

Adjust signal generator controls for

a 300-kc output signal at a level of

50 microvolt. Connect signal generator output to test set input.

Tune control unit for zero beat in

headset, then set BFO-OFF switch

to OFF. Set function switch to ADF.

Set vtvm to ac measuring range and

connect probe to the emitter of first

agc amplifier Q16 (fig. 2–3).

Set GONIO DRIVE switch to ON.

When the test set BEARING INDICATOR and LOOP SIMULATOR

dials have the same indication,, lock

the shaft of resolver servo motor B5.

Lock the shaft by stretching a rubber

hand around the large gear shown in

figure 2–8 and a corner of the receiver chassis.

(6)

(7)

(8)

TM 11-5826-225-25

Rotate the test set LOOP SIMULATOR dial clockwise as required for

an indication of 20 millivolts ac on

the vtvm. If necessary, increase the

signal generator output signal.

Turn variable resistor R131 (fig. 2-8)

fully clockwise.

Using vtvm, measure the signal voltages at the points indicated in the

following chart. If a voltage is appreciably less than indicated, check

transistors and associated circuit components. After these tests, adjust

variable resistor R131 ( para 3–20).

2-29
TM 11-5826-225-35

Figure 2-17 Receiver transistor voltage

diagram (part 1 of 2).

2-30 Change 5
TM 11-5826-225~35

Figure 2-17 Receiver transistor voltage

diagram (part 2 of 2).

equipment without physically unsoldering the

transistor leads. It requires considerable time

to unsolder and resolder transistor leads. In

addition, transistors can be damaged by heat

or accidental breaking of a lead.

c. Weak Signals. If signals are weak and

all tests fail to indicate a defective part, check

the alignment of the receiver. See chapter 9.

d. In-Circuit Resistance Measurements. If

transistors are the pluck-out type, make resistance measurements in these stages with the

transistors removed from the sockets, When

measuring the resistance of circuit elements

connected across

collector junction

consider polarity

the base-emitter or baseof any wired-in transistor,

of the ohmmeter and try

Change 5 2-31
TM 11-5826-225-35

measurements with the ohmmeter leads connected one way and then reverse the leads.

When in doubt about the value of resistance

measurements, check a receiver known to be

in good operating condition. Since all lowpower transistors of the pluck-out type operate on very low voltages, a capacitor seldom

causes trouble. If an IF transformer is suspected of having an open winding, remove the

associated transistor before making resistance

measurements. For all resistance measurements, use Multimeter TS–352/U. Set multimeter on the RX100 range.

Caution: If the receiver is inoperative in all

operating modes (no sound or bearing indication) and a shorted voltage regulator filter capacitor is suspected, check the resistance of

capacitors C88, C116, and C146 (figs. 2-6 and

2-7) before applying power.

e. Voltage Measurements. Make voltage

measurements in accordance with figure 2–17.

Transistors in the push-pull RF amplifier,

oscillator, bfo, and IF amplifier have collector

load impedances which present the proper load

at the resonant frequency but present such a

low dc resistance that no collector voltage can

be measured. In these transistor stages, a slight

shift in transistor characteristics may change

emitter and base-bias voltages from that indicated in figure 2–17. If this occurs, try another transistor. When making voltage measurements, use Multimeter ME-26/U or a vtvm

with equivalent characteristics,

f. Waveforms. Using Oscilloscope AN/

USM–140, make waveform checks and compare

them with the waveforms given in figure 2-18.

Waveform checks will help to isolate trouble

in the balanced modulator, synchronous filter,

agc circuit, and the servo amplifiers. Do not

connect the oscilloscope directly to the transistor pins or wires. Use a low capacity probe.

g. Illustrations. Use the main schematic diagram (fig. 5-10) in conjunction with the stage

and interunit schematic diagrams to circuit

trace and isolate the faulty part. For parts

location, refer to figures 2-3 through 2-16.

2-32

2-9. Additional Troubleshooting Data

a. Dc Resistances of Transformers and Coils.

The dc resistances of transformers and coils

are given in the chart below.
TM 11-5826-225-35

Transformer or coil Terminals Ohms

L1 -------------------------- 26

L3 ----------------- 1-2 28

2-3 2.1

L4 ----------------- 1-2 19

2-3 1.4

L5 ________________ 1-2 6.4

2-3 Less than 1

L6 --------------- ,,-------- 16

L8 ---------------- --------- Less than 1

L11 _______________ 1-2 54.5

L12 through L15 --------- --------- 46

L16 --------------.,-------- 62

L17 --------------- --------- 10

L18 ______________ ---------- Less than 1

L22 -------------- --------- 16

L24 _______________ ,--------- 26

L25 --------------- _________ 1.8

L26 ------------------------- Less than 1

Item Symptom

1

2

3

4

6

6

7

8

9

1

10

11

12

13

Tuning servo has a S1OW response and will not

reach a null.

On the 190- to 400-kc range, radio station fre

quency does not agree with dial calibrations of

control unit.

Spurious frequencies on all frequency ranges ____

BFO inoperative -----------------------------------

Bearing indicator will not reach null in adf mode

Low sensitivity in adf mode __________________

Loop and adf modes inoperative .-.. ___________

Intermittent operation in loop and adf modes ----

Bearing indicator pointer erratic on tail bearings

In ADF mode bearing indicator either has a slow

response or is inoperative.

Homing function weak and will not reach aural

null in loop mode.

Inoperative in all mode. ______________________

In loop mode:

(a) Bearing indicator rotates too slow when control unit

LOOP switch is in slow slew position.

(b) Bearing indicator rotates too fast when control unit

LOOP switch is in slow slew position, and/or indicator rotates too slow when control unit LOOP

switch is in fast slew position,

No manual control of RF gain ---;-----------

Audio output ● ignal present when control unit

GAIN control la in full counter-clockwise

position.

14

16

16 Little or no audio output ---------------------

Transformer or coil Termlnals Ohms

L27 -------------- ---------- 6.9

L28 -------------- ---------- 3.’7

L29 ______________ ---------- 2.5

L30 -------------- ---------- 1.2

L31 -------------- ---------- 2.6

1 I

b. Typical System Troubles Caused by Defective Receiver. The following chart lists symptoms that indicate improper equipment performance, The chart also lists a probable cause

in the receiver for each of these symptoms.

This chart does not include all probable causes

in the receiver for a given symptom, or probable causes in other components or in the aircraft wiring.

Probable Cause

Capacitor C74 coupled to control winding of tuning

servo motor MGl changes value.

Capacitor C37 in local oscillator circuit defective.

Local oscillator Q6 defective.

Capacitor C99 in bfo circuit defective. RF coil L16 open.

Bypass capacitor C82 (selected) on T18-1 defective.

Push-pull RF amplifiers Q2 and Q4 defective. Resolver

B3 defective.

f

Shorted winding in T18. The 110-cps oscillator Q22 or

lo -cps amplifler Q23 defective. Emitter bias resistor

R122 on Q23 defective by reason of capacitor C67

king shorted.

Bypass capacitor C5 on Tl, T2, and T3, defective.

Emitter bypass capacitor C6 on first RF amplifier

Q1 defective.

Capacitor at junction of emitter bias resistor R31 and

base-bias resistor R30, defective (fourth IF amplifler

Q10).

Resolver servo motor B5 has insufficient torque. Second

RF amplifier Q3 defective. Q17 bias adjust variable

resistor R131 out of adjustment.

Filter capacitor C146 in voltage regulator circuit defective. Second audio amplifier Q13 defective. Audio

coupling capacitor C83 defective.

Emitter bias resistor R107 on second IF amplifier Q8

defective.

(a) Resolver servo-amplifier bias resistor R133 (selected) has

too low a value. Capacitor c82 (selected) defective

(b) Resolver, servo-amplifier bias resistor R133 (selected) has

100 high a value. I

Rf coil L12 Open.

Diode CR1l in voltage regulator circuit oscillating.

Capacitor C78, connected between terminals 3 and 6 of

T20, defective.

Change 5 2-33
TM 11-5826-225-35

2-34 Figure 2-18. Receiver waveforms.
Figure 5-11

figure 2-2.

2-10.

2-11.

figure 2-19.

figures 2-20

TM 11–5826-225-3 5

c. Receiver Waveforms. Typical waveforms

at significant points in the receiver are show n

in figure 2– 18. Use oscilloscope AN/USM-140

when obtaining data for comparison with the

waveforms shown in figure 2–18. The waveforms in figure 2–18 were obtained under the

following conditions:

(3)

(4)

(5)

The 150PF–270PF control on the (6)

sense antenna adapter is set to

150PF.

The oscilloscope horizontal speed is

( 7 )

adjusted to obtain a waveform similar

to that shown in figure 2-18.

Except for bfo Q21, waveform data is

taken with Rf Signal Generator AN

URM-25( ) connected to the test set

as shown in figure 2–2. The AN

URM-25( ) is tuned for 200 kc (set

BFO–OFF switch on the test set to

ON and tune AN/URM-25( ) for a (8)

zero beat in the headset, then se t

BFO-OFF switch to OFF). The AN

URM-25( ) output is then adjusted

for 1,000 microvolts, modulated 30

percent at 400 cps.

For bfo Q21, do not connect RF Signal

Generator AX URM–25( ) and set

the BFO–OFF switch on the test set

to OFF.

Waveform data on Q17, Ql8, Q24,

an Q25 is obtained with servo moto r

B5 locked. After B5 is locked, by

blocking the gear train, adjust the

2–3 5
Figure 2-19.

TM 11-5826-225-35

Figure 2-19. Control unit test setup.

a. Tuning Meter Test. Set test set RECEIVERCONTROL switch to CONTROL and CONTROL

TEST switch to position 1. Set DC POWER switch to

ON. The tuning meter on the control unit under test

should indicate half scale and the panel and dials should

be illuminated. If the tuning meter indicates otherwise

or is inoperative, tuning meter M301 (fig. 2-20) is

defective.

b. Tuning Synchro Test.

(1) Set control unit function switch to the ADF

mode.

(2) Set control unit range switch to the 850-1750

position, Tune control unit to 850 kc. The test set

BEARING INDICATOR pointer should indicate 343

± 1 degree.

(3) Tune control unit until the FREQUENCY

dial hairline bisects the small zero between 1,400 and

1,500 kc, The test set BEARING INDICATOR should

indicate 239 ± 1 degree,

(4) Tune control unit to 1700 kc. The BEARING

INDICATOR should indicate 203 ± 2 degrees.

(5) If the BEARING INDICATOR pointer indication does agree with the normal indications obtained in the above tests, either tuning synchro B301 is

defective or the dial and synchro are out of alignment.

c. Resistance and Continuity Tests.

(1) Set test set DC POWER switch to OFF. Connect test leads of multimeter to the two panel connectors on the test set marked CONTROL TEST and set

multimeter to the RX 1 ohms range.

(2) Set test set CONTROL TEST switch to position 1. The multimeter should indicate zero ohms.

(3) Set multimeter to the RX10 range. Turn control unit LOOP control to the first position left and

right. The multimeter should indicate 4,700 ohms for

both low speed positions of the LOOP control.

(4) If the multimeter indications are not as

specified in (2) and (3) above, LOOP switch S303 is

defective.

(5) Set test set CONTROL TEST switch to position 2, With the BFO-OFF switch in OFF position, the

multimeter should indicate infinity. Set BFO-OFF

switch to BFO. An ohmmeter reading other than zero

indicates that BFO-OFF switch S301 is defective,

(6) Set CONTROL TEST switc h

to position 3. Set control unit function

switch t o ADF . T h e multi meter

2-36 Change 4
TM 11-5826-225-35

Figure 2–20. Control unit, front view.

(7)

should read zero ohms. A reading (8)

other than zero ohms indicates that

function switch wafer S302-A is not

making contact.

Set function switch to ANT and

LOOP positions. The multimeter

should indicate from 5,000 ohms to

zero ohms as the GAIN control is (9)

turned clockwise. A multimeter reading other than the above indicates

either that function switch wafer

S302-A or RF gain variable resistor R301-C is defective. (lo)

Set CONTROL TEST switch to position 4. Turn control unit GAIN

control fully counterclockwise. With

the function switch in either ADF or

ANT position, the multimeter should

read 5,000 ohms which is the resistance of variable resistor R301–C.

Set function switch to LOOP. A multimeter reading much different than

5,470 ohms indicates that resistor

R303 in series with R301–C is defective.

Set CONTROL TEST switch to posi2-37
TM 11-5826-225-35

(11)

(12)

2-28

Figure 2-21. Control unit, top view.

tion 5 and set function switch to

ADF. As the GAIN control is rotated

clockwise, the multimeter should indicate from 600 ohms to zero ohms. A

multimeter reading other than specified indicates trouble in the bridged

T-attenuator comprising R301-A,

R301-B, R304, and R305. (13)

Set function switch to either LOOP

or ANT position. The multimeter

should indicate zero ohms. Any other

reading indicates that function switch

wafer S302-A is not making contact. (14)

Set CONTROL TEST switch to position 6 and function switch to either

ANT or LOOP position. The multimeter should read infinity. With the

function switch set to ADF, the multimeter should read approximately 650

ohms for any GAIN control setting

or R301–A and R301–B.

Set CONTROL TEST switch to position 7 and set function to ADF, ANT,

or LOOP position. The multimeter

should indicate zero ohms. Set function switch to OFF. The multimeter

should read infinity.

Set CONTROL TEST to position 8.

The multimeter should read infinity

with the function switch set to OFF
TM 11-5826-225-35

Figure 2-22. Control unit, left side view.

(15)

(16)

(17)

(18)

and ADF positions and indicate zero

ohms for LOOP and ANT positions.

Set CONTROL TEST switch to position 9. The multimeter should indicate zero ohms with the function

switch set to ADF or LOOP position

and infinity for OFF or ANT position.

Set CONTROL TEST switch to position 10. The multimeter should indicate infinity with the function switch

set to OFF or LOOP position and zero

ohms for ADF or ANT positions.

If the test results are not as specified

in steps (13) through (16), function

switch S302 is defective.

Set CONTROL TEST switch to position 11. The multimeter should indicate 25 ohms with the control unit

range switch set to the 190- to 400-

kc position and zero ohms for the

other two ranges.

(19) Set CONTROL TEST switch to position 12. The multimeter should indicate 25 ohms with the range switch

set to the 400- to 850-kc range and

zero ohms for the other two ranges.

(20) Set CONTROL TEST switch to position 13. The multimeter should indicate 25 ohms with the range switch

set to the 850- to 1750-kc range and

zero ohms for the other two ranges.

(21 ) If the test results are not as specified

in steps (18) through (20), either

range switch S304 or resistor R308

is defective.

2-12. Localizing Troubles

If any local resistance measurements are necessary after using the test set, refer to disassembly and reassembly procedures in chapter

3.

Change 1 2-39
TM 11-5826-225-35

Section IV. TROUBLESHOOTING MOUNTING MT–3605/ARN-83 AND INVERTER,

POWER, STATIC CV-2128/ARN-83

2-13. Test Setup

The only troubles that can occur in the receiver mount are damage to connectors (JI

and J2 of fig. 2–24) and aircraft wiring connections to the receiver mount. Therefore, the

remainder of this section will be devoted to

the inverter. All tests on the inverter require

connections to Test Set, Direction Finder Set

AN/ARM–93 and the source of 27.5-volt dc

power used for testing the receiver and control

unit. After making certain the test set DC

POWER switch is set to OFF, remove the

plate at the top of the test set front panel

marked INVERTER. Loosen the two retaining

screws on the inverter supplied with the test

set and remove the inverter.

a. Remove the inverter mounted in Mounting MT–3605/ARN–83 (fig. 2–24).

b. Connect one end of the test set cable W4

to the test set and the other end to connector

PI on the inverter (fig. 2–25). The length of

the cable will permit bench tests on the inverter. The inverter test setup is illustrated in

figure 2–23.

2-14. Localizing Troubles

a. Set test set DC POWER switch to ON

and allow 5 minutes for inverter warmup. The

other test set controls may be in any position.

b. Set controls on Multimeter ME-26/U

(vtvm) to a range suitable for measuring 26

volts ac. Connect the common test lead of vtvm

to a convenient ground on the test set front

panel. Insert the tip of the vtvm ac test probe

into the center of the test set panel fuse holder

marked 1A. The voltage should be 26 ±2.0 volts ac.

c. Set TIME UNIT switch of Frequency

Meter AN/USM–26 (counter) to lKC, FUNCTION SELECTOR to FREQUENCY, and

STD. GATE TIME SEC. switch to 1 second.

Connect ground lead of counter to a ground

on the test set front panel. Connect SIGNAL

INPUT of counter to the fuse holder specified

in b above. The counter frequency read out

should be 400 ±40 cps.

Figure 2-23. Inverter test setup.

2-40 Change 5
Figure 2-24. Mounting with inverter installed.

2-15. Isolating Trouble

TM 11-5826-225-35

Within Stage

If the trouble has been traced to the inverter 

through the checks made in paragraph 2-14, use

the following techniques to isolate the stage or

part at fault.

a. Test the transistors with Transistor

Tester TS-1836/U (figs. 2-25 and 2-26).

b. Make voltage measurements on the transistors and compare them with those given in

figure 2-27. Refer also to the dc resistance of

transformers and coils (d below).

c. If necessary, adjust R1 for 26 ±2.0 volts ac.

d. Dc resistances of transformers and coils.

Change 5 2-41
TM 11-5826-225-35

Figure 2–25. Inverter, bottom view.

Figure 2–26. Inverter, end view.

2-42
Figure 2-27.

TM 11-5826-225-35

Figure 2-27. Inverter voltage diagram

Section V. TROUBLESHOOTING ANTENNA AS–1863/ARN–83

2–16. Test Setup

Troubleshooting Antenna AS-1863/ARN-83

consists of measuring the Q of the loop coils

using ‘Q Meter TS–617/U and the loop test

fixture supplied with Test Set, Direction Finder

Set AN/ARM-93. The loop antenna test setup

is shown in figure 2–28.

a. Mount Q Meter TS-617/U on the four

large banana plugs (P2 through P5) of the

test set loop test fixture. Connect J1 of the

loop antenna to connector P1 of the loop test

fixture.

b. Set the loop test fixture selector switch to

position 1.

c. Set controls of Q meter for a frequency

of 1.0 megacycle. Adjust capacity control for

maximum Q. The capacity required for maximum Q should be 140 to 280 picofarads.

d. Set test fixture switch to position 2.

e. Using the same frequency as in c above,

adjust Q meter capacity control for maximum

Q. The capacity required for maximum Q

should be 140 to 280 picofarads.

2-43
TM 11-5826-225-35

2-44
TM 11–5826-225–35

CHAPTER 3

REPAIRS AND ALIGNMENT

Section 1.

3–1. General Parts Replacement Techniques

The following general precautions should be

observed when replacing parts in this equipment.

a. When soldering or unsoldering transistor

leads or precision resistors, solder quickly to

allow as little heat conduction as possible.

Whenever wiring permits, use a heat sink

(such as a long nose pliers) between the solder

joint and the part. Use approximately the same

length and dress of leads as used originally.

b. Use a pencil-type iron with a 25-watt

maximum capacity when working on replacement of non pluck-out transistors. If the iron

must be used with ac, use an isolation transformer between the iron and the line. Check

soldering irons for shorts to the iron tip before using. Do not use a soldering gun as damaging voltages can be induced in components.

c. In some cases power transistors ar e

mounted on heat sinks. When replacing power

transistors, always replace the insulating

washer between the transistors and the heat

sink if an insulator is used. Before installing

the mica or fiber washers, treat them with a

film of silicone fluid or equivalent to help in

the transfer of heat. After the transistor is

mounted and before making connections, check

from transistor case to ground for effective

insulation.

d. Whenever an electrical part such as a

resistor, capacitor, or a coil is to be removed,

note the exact position of the part before removing it. Replace the part in the same p{wition.

REPAIRS

e. When tightening the two setscrews in

a collar-type clamp, the setscrews must be

tightened against the center of the gear (or

other mechanical part) quarter. segments.

3–2. Removal and Replacement Techniques

The procedures for removing receiver subassemblies and disassembling the receiver gear

train subassembly are described in paragraph

3-3. The corresponding reassembly and replacement procedures are described in paragraph 3-4. Paragraph 3-4 also includes instructions for lubrication that is performe d

during receiver reassembly and replacement.

The procedures for disassembling the control

unit are described in paragraph 3–5. Reassembly and lubrication that is performed during reassembly of the control unit are described in paragraph 3–6. The loop antenna

cannot be disassembled and disassembly of the

inverter and receiver mount are obvious,

3–3. Disassembly of Receiver

a. Removal of Dust cover .

(1) Loosen two screws (fig. 2–1) at front

of the receiver and one screw at rear.

(2) Pull off dust cover.

b. Removal of Power Supply and Servo

Compartment .

(1) Remove four screws (A, fig. 3-1).

(2) Swing out power supply and servo

compartment.

(3) Remove four screws (A, fig. 3-2), and

remove the compartment.

c. Removal of Switch Shaft.

(1) Remove switch shaft cover (fig. 2–1)

3–1
TM 11-5826-225-35

( 2 )

(3)

(4)

from switch shaft access hole on front

panel of receiver.

Remove three screws and three lockwashers which secure RF shield to

left side of receiver, and remove RF

shield.

Loosen two setscrews on switch shaft

coupler (fig. 3–1) which connects

switch shaft to gear train subassembly.

Slide switch shaft out through access

hole in front panel of receiver ((1)

above).

d. Removal of Push-Pull RF Amplifier Subassembly.

(1) Remove switch shaft (c above).

(2) Remove one screw and lockwasher (B,

fig. 3–1) “and three screws (B, fig.

3-2).

(3) Pull out subassembly.

e. Removal of Second RF Amplifier and

balanced Modulator Subassembly.

(1) Remove switch shaft (c above).

(2) Remove one screw and lockwasher (C,

fig. 3–1) and three screws (C, fig.

3–2) .

(3) Pull out subassembly.

f. Removal of First RF Amplifier Subassembly.

(1) Remove switch shaft (c above).

(2) Remove one screw and lockwasher

(D, fig. 3-1) and three screws (D,

fig. 3-2).

(3) Pull out subassembly.

g. Removal of Mixer Subassembly.

(1) Remove switch shaft (c above).

(2) Remove one screw and lockwasher (E,

fig. 3–1) and five screws (E, fig. 3–2).

(3) Pull out subassembly.

h. Removal of Local Oscillator Subassembly.

(1)

( 2 )

(3)

3 - 2

Remove switch shaft (c above).

Remove one screw and lockwasher (F,

fig. 3-1) and three screws (F, fig.

3–2 ) .

Pull out subassembly.

i. Removal of IF Amplifier Subs.ss~mbly.

(1) Remove seven screws (G, fig. 3-1).

(2) Pull out subassembly.

j. Removal of Audio Frequency Amplifier

Subassembly.

(1) Remove five screws (H, fig. 3-2).

(2) Pull out subassembly.

k. Removal of Bfo Subassembly.

(1) Loosen two screws (J, fig. 3-2).

(2) Pull out subassembly.

1. Removal of Tuning Capacitor Subassembly.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

Remove two screws (101, fig. 5-16)

and two lockwashers ( 100) which secure cover ( 102) of gear train subassembly, and remove cover.

Remove capscrew and lockwasher (K,

fig. 3–1) which secures tuning capacitor subassembly to gear train subassembly.

Loosen two setscrews on tuning capacitor shaft collar (fig. 3–1) which is

part of gear train subassembly.

Loosen lowest screw of four screws

(A, fig. 3-2) approximately three

turns.

Remove screw and lockwasher (L,

fig. 3-2) .

Slide tuning capacitor subassembly

towards front of receiver. Be careful

that pair of tuning capacitor drive

gears (fig. 3-1) in gear train subassembly do not bind on shaft of tuning capacitor subassembly. Pair of

84-tooth spur gears and tuning capacitor shaft collar may fall free.

Pull tuning capacitor subassembly out.

It may be necessary to remove four

screws (M, fig. 3-1) and press down

on bottom of receiver chassis to allow

removal of subassembly.

(2)

(3)

Remove power supply and servo

compartment (b above).

Remove switch shaft (c above).

Perform procedures in l (1), (2), and

(3) above.
TM11-5826-225-35

(4)

(5)

(6)

Remove two screw’s (N, fig. 3–1) on

top of receiver chassis.

Remove two screws on bottom of receiver chassis which are directly opposite from two screw in (4) above.

Slide gear train subassembly toward

rear of receiver until subassembly is

free.

n. Disassembly of Gear Train Subassembly

(fig. 5-16).

Note. Some of the items of the gear train subassembly are removed or loosened when the subassembly is

removed from the receiver chassis (m above). These

items are two setscrews (119), two setscrews (68), two

screws (101), two Iockwashers (100), and cover (102).

Removal or loosening of these items are not repeated

in the disassembly procedures below.

(1)

(2)

(3)

( 1)

( 5)

( 6)

( 7)

( 8)

( 9)

 (10)

 (11)

 (12)

Remove two screws ( 116) anti two

lockwashers ( 115) from front gear

plate ( 103).

Remove screw ( 104) and lockwasher

(105) at upper right corner of front

gear plate.

Remove scre

w (111), lockwasher

(112), flat washer (113), and dowel

(114) at lower right corner of front

gear plate.

Remove screw (122) and lockwasher

(123) at upper left corner of front

gear plate.

Remove screw (124)

. lockwasher

(l25), flat washer (126), and dowel

(127) at lower left corner of front

gear plate.

Remove two screws (120) and two

lockwashers (121) that secure side

plate (72) to front gear plate.

Remove screw (38) anti lockwashe

r

(37). Spacer (81) will be free.

Loosen two setscrews (97) on collar

(98).

Remove extension spring (117)

Loosen two setscrews (119) on switch

shaft coupler (118), and remove

switch shaft coupler.

Pull off front gear plate (103) and

attached parts.

Remove three screws (109), three

(13)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

(23)

(21)

(25)

(26)

(27)

(28)

(29)

(30)

3-3
3-4.

fig. 5-16

TM 11–5826-225-35

(31)

(32)

(33 )

(34)

(35)

(36 )

(37)

(38)

(39)

(40)

(41)

(42)

(43)

(44 )

(45 )

(46 )

3–4

(47)

(48)

(50)

(1)

(2)
TM 11-5826-225-3 5

Figure 3-1. Receiver, left side view, dust

cover removed.

3-5
TM 11-5826-225-35

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

Figure 3-2. Receiver, right side view, dust

cover removed.

plate with two screws (120) and two

lockwashers (121).

Mount housing (99) to front gear

plate with screw (104), lockwasher

(105), screw (111), lockwasher (112),

flat washer (113), and dowel (114).

Tighten screw (111) first.

Mount two screws ( 116) and two lockwashers (115) to f rent gear plate.

Mount resolver B3 (110) to front gear

plate with three screws ( 109), three

lockwashers (108), three flat washers

(107), and three spacers (106).

Place spur gear assembly (84) in

front gear plate.

Place spur gear assembly (80) in

front gear plate.

Place spur gear assembly (82) in

front gear plate.

Place spur gear assembly (83) in

front gear plate.

Place retaining ring (76) on spur

gear assembly (77), and place spur

gear assembly (77 ) in front gear

plate.

(13)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

Place spur gear assembly (79) in

front gear plate.

Place spur gear assembly (76) in

front gear plate.

Place spur gear assembly (78) in

front gear plate.

Place spur gear assembly (70) in

front gear plate.

Place spur gear assembly

front gear plate.

Place spur gear assembly

front gear plate.

Place spur gear assembly

front gear plate.

Place load spring (95) on

71) in

73) in

74) in

hubbed

spur gear (94). Insert one end of load

spring into hole in hubbed spur gear

(94).

Place spur gear (96) on assembly

of (20) above. Position spur gear ( 96)

so that other end of load spring (95)

fits into hole in spur gear (96).

Place collar (98) on hub of hubbed

spur gear (94). The chamfered end of

3 - 6
(23)

(24)

(25)

(26)

(27)

(28)

(29)

(30)

(31)

(32)

(33)

collar should be against spur gear

(96).

Hold hubbed spur gear (94), and

rotate spur gear (96) six teeth clockwise (right-hand loading), as viewed

from spur gear (96) end. Take up any

slack before counting the six teeth.

Keep right-hand loading as in (23)

above, and place assembly of items (94

through 98) on shaft of resolver B3

(110). Mesh spur gears (94 and 96)

with 17-tooth gear of spur gear assembly (84) which is nearest resolver

B3.

Tighten two setscrews (97, lock). Do

not tighten setscrews on openings in

split hub of hubbed spur gear (94).

Tighten setscrews on solid portion of

split hub.

Mount motor 132 (39) to rear gear

plate (58) with two screws (85), two

lockwashers (86), and two fla t

washers (87).

Attach screws (8) and terminal lugs

(9) to tuning synchro control transformer B1 (10).

Mount B1 (10) to rear gear plate

(58) with three screws (5), three

lockwashers (6), and three rim clamps

(7).

Mount servo motor-generator set MG1

(17) to rear gear plate with three

screws (18), three lockwashers (19),

and three rim clamps (20).

Mount servo motor B5 (47) to rear

gear plate with two screws (44), two

loci-mashers (45), and two rim clamps

(46).

Attach screws (48) and terminal lugs

(49) to bearing synchro transmitter

B4 (50).

Mount B4 (50) to rear gear plate

with three screws (51), three lockwashers (52), and three rim clamps

(53)

Place load spring (63) on hubbed

spur gear (64). Insert one end of load

(34)

(35)

(36)

(37)

(38)

(39)

(40)

(41)

(42)

(43)

(44)

(45)

(46)

TM 11-5826-225-35

spring into hole in hubbed spur gear

(64).

Place spur gear (62) on assembly of

(33) above. Position spur gear (62)

so that other end of load spring (63)

fits into hole in spur gear (62).

Place collar (61) on hub of hubbed

spur gear (64). The chamfered end of

collar should be against spur gear

(62).

Place assembly (60 through 64) on

shaft of tuning synchro control transformer B1.

Lightly tighten two setscrews (60)

just enought to hold assembly ((36)

above) in place.

Place load spring (91) on hub of

hubbed spur gear (92). Insert one end

of load spring into hole in hubbed

spur gear (92).

Place spur gear (90) on assembly of

(38) above. Position spur gear (90)

so that other end of load spring (91)

fits into hole in spur gear (90).

Place collar (89) on hub of hubbed

spur gear (92). The chamfered end of

collar should be against spur gear

(90).

Place assembly of items (88 through

92) on shaft of bearing synchro

transmitter B4 (50).

Lightly tighten two setscrews (88)

just enough to hold assembly ((41)

above) in place.

Attach two extension springs (66) to

hubbed tuning capacitor drive gear

(65).

Place tuning capacitor drive gear

(67) on hub of hubbed tuning capacitor drive gear (65). Countersunk holes

in gear (67) go toward hubbed gear

(65). Attach other ends of extension

springs (66) to gear (67).

Place collar (69) on huh of hubbed

gear (65), and lightly tighten two setscrews (68).

Place assembly of items (65 through

3-7
TM 11-5826-226-35

(47)

(48)

(49)

(50)

(51)

(52)

(53)

(54)

(55)

(56)

(57)

69) in position near spur gear assembly (70).

Place rear gear plate (58) and at

tached items onto items assembled to

front gear plate (103). All shafts

must seat properly in bearings in

rear gear plate. Mesh all gears. Spur

gears (65 and 67) should mesh with

one of 17-tooth gears on spur gear

assembly (70).

Place spacer (81) in position between

two gear plates, and secure with

screw (38) and lockwasher (37).

Replace screw (l), lockwasher (2),

flat washer (3), and dowel (4) on

rear gear plate.

Replace screw (11), lockwasher (12),

flat washer (13), and terminal post

(14) on rear gear plate.

Replace two screws (15) and two

lockwashers (16) on rear gear plate.

Replace screw (40), lockwasher (41),

flat washer (42), and dowel (43) on

rear gear plate,

Replace screw (54), lockwasher (55),

flat washer (56), and terminal post

(57) on rear gear plate.

Insert electrical contact (93) against

inside of housing (99), with the letter

“X” marked on the switch wafer

away from rear gear plate. Hooked

end of electrical contact fits against

bottom of housing, with hook facing

away from housing. Curved center of

electrical contact should make contact with shaft of B4 (50) and shaft

of B3 (110).

Place switch shaft coupler (118) on

shaft of spur gear assembly (77), and

tighten two setscrews (119, lock)

nearest f rent gear plate (103). Do not

tighten other two setscrews (119).

Replace extension spring (117) on

switch shaft coupler (118).

Attach switch plate (27) to rear gear

plate with two screws (33), two lockwashers (34), two flat washers (35),

and two switch clamps (36).

(58)

(59)

(60)

(61)

(62)

(63)

(64)

(65)

Place switch wafer S1–K (28) on

shaft of spur gear assembly (77),

with the letter “X” marked on the

wafer away from gear plate. Note the

position of the small notch in the

shaft hole of the rotor of the switch

wafer.

Position the rotor of switch S1–L

(24) so that the small notch in the

shaft hole of the switch wafer is in

the same position as the notch in

switch wafer, S1–K (28).

Place switch wafer S1-L (24) on

shaft of spur gear assembly (77).

Check that the notches in the shaft

holes of switch wafers S1-L and SlK are on the same flat of the shaft of

spur gear assembly (77),

Position switch wafers S1-L (24)

and S1–K (28) so that the letter “X”

marked on the switch wafers is nearest servo motor-generator set MG1

(17). Then secure switch wafers to

rear gear plate with two screws (21),

two nonmetallic washers (22), two

spacers (25), and two spacers (26).

Position rotor of switch wafer S1-M

(23) so that the small notch in the

shaft hole of the switch wafer is in

the same position as the notches in

switch wafers S1-L (24) and S1–K

(28).

Place switch wafer S1-M (23) on

shaft of spur gear assembly (77),

with the letter “X” marked on wafer

away from rear gear plate. Check

that notches in shaft holes of S1-M,

S1–L, and S1–K are on same flat of

shaft.

Position switch wafer S1–M (23) so

that the letter “X” on the wafer is

nearest MG1 (17). Then secure S1–M

to switch plate (27) with two screws

(32), two nonmetallic washers (31),

four nonmetallic washers (30), and

two spacers (29).

Loosen two setscrews (60) on collar

(61).

3-8
Fig. 3-2

3-1

(66)

(67)

(68)

(69)

(70)

Pull assembly of items (60 through

64) toward front gear plate (103)

until spur gears (62 and 64) are unmeshed from 17-tooth gear on spur

gear assembly (70).

Hold hubbed spur gear (64), and rotate spur gear (62) five teeth clockwise (right-hand loading), as viewed

from spur gear (62) end. Take up any

slack before counting the five teeth.

Keep right-hand loading as in (67)

above, and push assembly (60 through

64) toward rear gear plate (58). Remesh gears (62 and 64) with 17-

tooth gear on spur gear assembly

(70).

Tighten two setscrews (60, lock). Do

not tighten setscrews on openings in

split hub of hubbed spur gear (64).

Tighten setscrews on solid portion of

split hub.

Apply a small amount of the following mixture to the teeth of all gears.

Wipe off ail excess.

(a) 25 parts by weight of grease (MILG-3278A).

(b) 37 parts by weight of butyl alcohol.

(c) 37 parts by weight of xylene.

Note. Items 65 through 69 are adjusted

after the tuning capacitor subassembly is

replaced (d below). Items 88 through 92

are adjusted during adjustment and synchronization of the resolver servo system

(para 3-18). Items 100, 101, and 102 are

replaced after all subassemblies are replaced.

c. Replacement of Gear Train Assembly.

Note. Replace the gear train assembly before replac-0

ing the tuninig capacitor subassemlby (d below).

switch shaft (m below), or power supply and servo

compartment (n below).

(1)

(2)

(3)

TM 11-5826-225-35

d. Replacement of Tuning Capacitor Subassembly.

Note. Replace the gear train subassembly (c above)

before replacing the tuning capacitor subassembly.

(l)’

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(l0)

Replace tuning capacitor subassembly (fig. 3-1) in receiver chassis. Retighten four screws (M) if they were

loosened during removal of tuning capacitor subassembly.

Loosen two setscrews on tuning capacitor shaft collar (fig. 3–1) in gear

train subassembly. This collar is

shown as item 69 in figure 5–16.

Loosen lowest of four screws (A, fig.

3-2) approximately three turns if

power supply and servo compartment

has been replaced.

Slide tuning capacitor subassembly.

toward gear train assembly. While

doing so, hold assembly of tuning capacitor shaft collar and tuning capacitor drive gears (fig. 3-1) so that

shaft of tuning capacitor subassembly

fits into hub of one of the tuning capacitor drive gears.

Replace capscrew and lockwasher (K)

that secures tuning capacitor subassembly to gear train subassembly.

Replace screw and lockwasher (L, fig.

3-2).

Retighten lowest of four screws ((3)

aove) .

Move tuning capacitor drive gears and

tuning capacitor shaft collar (fig.

3-1) toward rear of receiver (toward

rear gear place (58, fig. 5-16) of gear

train subassembly until drive gears

are unmeshed from spur gear assembly (70) in gear train subassembly.

With drive gears unmeshed, hold

hubbed tuning capacitor drive gear

(65) and rotate tuning capacitor drive

gear (67) four teeth clockwise (righthand loading), as viewed from gear

(67) end.

Keep loading in (9) above, and remesh tuning capacitor drive gears (65

and 67) with spur gear assembly

(70) .

3-9
fig. 3-1

fig.2-1

fig. 3-1

fig. 3-1

fig. 3-1

fig. 3-2

fig. 3-1

fig. 3-1

3-2

TM 11-5826-225-35

(11) Check that shaft of tuning capacitor

subassembly fis into hub of tuning

capacitor drive feaar (65). Then

tighten two setscrews 68, lock).

Final adjustment of the tuning capacitor subassembly is performed in

paragraph 3-12.

e. Replacement of Bfo Subassembly.

(1) Position subassembly (fig. 3-2) on

receiver chassis.

(2) Replace five screws (J).

f. Replacement of Audio Frequency Amplifier Subassembly.

(1) Position subassembly (fig 3-2) on

receiver chassis.

(2) Replace five screws (H, lock).

g. Replacement of IF Amplifier Subassembly.

(1) Position subassembly (fig. 3-1) on receiver chassis.

(2) Replace seven screws (G, lock).

h. Replacement of Local Oscillator Assembly

(1)

(2)

Position subassembly (fig. 3-1) on receiver chassis.

Replace one screw and lockwasher (E,

fig. 3-1) and five screws (E, fig. 3-2.

lick). Do not tighten screws fully until switch shaft (m below) has been replaced .

i. Replacement of Mixer Subassembly.

(1)

(2)

(1)

(2)

Position subassembly (fig. 3-1) on receiver chassis.

Replace one screw and lockwasher (C,

fig. 3-1) and three screws (C, fig.

3-2, lock). Do not tighten screws fully

until switch shaft (m below) has been

replaced.

l. Repalcement o f Push-Pull RF Amplifier

Subassembly.

(1) Position subassembly (fig. 3-1) on receiver chassis.

fig. 3-1) and three screws (B, fig.

3-2). Do not tighten screws fully until

switch shaft (m below) has been replaced.

placement of Swircth Shaft.

(2)

(1)

3-1 0
(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

Tighten all screws on subassemblies in

(1) abet’e, except for gear train subassembly. Tighten screws which are in

depressed area on left side of receiver

(fig. 3–2) first, and then tighten reremaining screw.

Secure RF shield to left side of receiver with three screws and three

lockwashers.

Rotate switch shaft manually. Switch

shaft should rotate smoothly and

easily, and switch wafers should not

bind. If necessary, loosen screws

which secure subassemblies, reposition subassemblies slightly, and retighten screws.

Remove RF shield ((6) above).

Insert end of switch shaft into switch

shaft coupler (fig. 3–1) on gear train

subassembly.

Rotate switch shaft so that flats of

switch shaft are aligned with flats of

shaft of spur gear assembly (77, fig.

5–16). Align flats of shafts so that

notches in switch wafers of subassemblies in (1) above are also aligned.

This includes wafer switches S1-K,

S1-L, and S1–M (28, 24, 23) in gear

train subassembly. The tighten two

setscrews (119, lock) on switch shaft

coupler (118) which secure switch

shaft. One of setscrew-s (119) should

seat on one of flats of switch shaft.

Rotate switch shaft so that switch

wafers are positioned as shown in

schematic diagram of receiver (fig.

5-l0).

Lubricate rotors of all switch wafers

with the following mixture. Apply

lubricant with a small camel’s-hair

brush, and remove all excess with a

clean, lint free cloth.

(a) 25 parts by weight of grease, Rylson

No. 2 E.P.

(b) 75 parts by weight of Stanisol sol-

(13)

(14)

vent.

Replace RF shield ((6) above).

Replace switch shaft cover

on front panel of receiver,

(fig. 2-1)

TM 11–5826–225-35

n. Replacement of Power Supply and Servo

Compartment.

(1) Replace gear train subassembly (c

above) before replacing power supply

and servo compartment ( fig. 3–2).

(2) Replace four screws (A, fig. 3-1, lock).

o. Replacement of Dust Cover.

(1) Slide dust cover over receiver chassis,

(2) Tighten two screws (fig, 2-1) at front

of receiver and one screw at rear.

3–5. Disassembly of Control Unit

Note. Refer to figure 5–17 throughout the disassembly

of the control unit.

a. Removal of Front Panel.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(lo)

(11)

(12)

Loosen four setscrews (96 and 101),

and remove TUNE knob (97) and

GAIN knob (102) from their shafts.

Loosen four setscrews (98, 100, and

104) and remove knobs (94, 99, and

105).

Remove two screws (108).

Remove two screws (106) and two

rubber washers (107).

Remove front panel (93) from the

control unit.

Loosen two Dzus fasteners (1) located

on rear cover (2), and slide rear

cover (2) off the control unit,

Slide the panel light assembly (92)

away from front subpanel assembly

(88) far enough to permit unsoldering

of the two panel lamp leads. Unsolder

and tag these leads,

Remove the panel light assembly (92)

from the control unit.

Remove four screws (112), and four

lockwashers (112).

Remove nut (114) and lockwasher

(115) securing toggle switch (133)

to front subpanel assembly (88).

Slide the front subpanel assembly

(88) away from frame (136) far

enough to permit unsoldering the leads

from ammeter (90). Unsolder and tag

these leads.

Remove front subpanel

from the control unit.

assembly (88)

3-11
TM 11-5826-225-35

(13) Remove two screws (91) and remove

ammeter (90) from front subpanel

assembly (88).

b. Removal of Attenuator. (R301).

(1) Loosen two Dzus fasteners (1) located

on rear cover (2), and slide the rear

cover (2) off the control unit.

(2) Loosen two setscrews (161), and remove crown gear (162) from the shaft

on the variable attenuator (166).

(3) Remove nut (163) and lockwasher

(164), and remove variable attenuator

(166).

c. Removal of Function Switch (S302).

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

Remove the front panel as described

in a above.

Remove the attenuator, R301 (b

above).

Remove retaining ring (141) from the

shaft of spur gear assembly (146).

Remove spur gear assembly (146)

from frame (136).

Remove spring (126) from th e

grooved pin on frame (136).

Remove detent follower (125) from

the detent holder on frame (136).

Remove switch detent (124) from the

front of frame (136).

Remove two screws (142), two lockwashers (143), two nonmetalli c

washers (144), switch section (140),

two spacers (137), switch section

(139); and two more spacers (138).

d, Removal of LOOP switch (S303).

(1)

(2)

(3)

(-4)

(5)

Remove the front panel (a above).

Remove the attenuator (R301) (b

above),

Remove nut (130) and lockwasher

(129) from rotary switch (151).

Remove rotary switch (151) from

frame (136).

Remove two nuts (160), two lockwashers (159), two flat washers

(158), and terminal board (157) from

rotary switch (151).

e. Removal of Tuning Gear Train.

(1) Remove the front panel (a above).

3-12

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(lo)

(11)

Remove three screws (5) and three

lockwashers (6) securing retaining

plate (8) to frame (136).

Remove fixed resistor (12) from retaining plate (8) by removing screw

(7).

Remove four screws (20) and nuts

(17) securing connector (21) to retaining plate (8).

Remove the retaining plate (8).

Loosen setscrews (71) and (75) on

collars (72) and (76), respectively.

Pull out stop hub assembly (57), along

with five stop washers (59, 61, 63, 65,

and 67) and five flat washers (58,60,

62, 64, and 66), from the rear of

frame (136).

Remove two collars (72 and 76), flat

washer (70), and worm gear (73).

Loosen two setscrews (44) in collar

(45) and remove spur gear (43) from

shaft of helical gear assembly (52).

Loosen two setscrews (53) in collar

(54) and remove spur gear (120)

from shaft of helical gear assembly

(52).

Remove washers (117, 118, and 119).

(12)

The number of washers (117) may be

more or less than shown. Record the

number for reassembly.

Remove helical gear assembly (52)

from frame (136).

f. Removal of Tuning Synchro (B301).

(1)

(2)

(3)

(4)

(5)

(6)

Loosen two Dxus fasteners (1) located on rear cover (2), and slide the

rear cover (2) off the control unit.

Remove three screws (5) and three

lockwashers (6) securing retaining

plate (8) to frame (136).

Remove fixed resistor (12) from retaining plate (8) by removing screw

(7).

Remove four screws (20) and nuts

(17) securing connector (21) to the

retaining plate (8),

Remove the retaining plate (8).

Loosen two setscrews (1) on collar
(7)

(8)

(9)

(l0)

(45), and remove spur gear (43)

from shaft of helical gear (52).

Note. If setscrews (44) cannot be reached,

the tuning gear train must be disassembled

(e above).

Loosen two setscrews ( 127) on collar

(128), and remove spur gears (121,

123) from the shaft of transmitter

synchro (156).

Remove collar (128).

Loosen the three screws ( 155) located

around transmitter synchro (156) at

the shaft end.

Orient three rim-clinching clamps

(153) to permit removal of transmitter synchro (156) and remove the

transmitter synchro (156).

g. Removal of Dial Drum.

(1)

(2)

(3)

(4)

(5)

(6)

Set the range switch to 190-400.

Remove the front panel (a above).

Remove two screws (132), two lockwashers (131), two flat washers

(134), and remove dial mask ( 135)

from frame (136).

Loosen two setscrews (35) on collar

(37).

Remove spur gear assembly (30),

load spring (31), spur gear (32), and

retaining ring (33) from the top of

frame (136).

Remove dial drum (41) from frame

(136) using care not to distort spring

(40).

h. Removal of Range Switch (S304).

(1)

(2)

(3)

(4)

Remove the front panel (a above).

Remove two screws (87), two nonmetallic screws (86), two lockwashers

(85), and remove switch section (84).

Remove two spacers (83).

If it is desired to remove switch detent (82) and detent followers (56),

perform the following procedure:

(a) Remove three screws (5) and three

lockwashers (6) securing retaining plate (8) to frame (136).

(b) Remove fixed resistor (12) from

retaining plate (8) by removing

screw (7).

(c)

(d)

(f’)

(f)

(g)

(h)

(i)

(j)

(k)

(1)

TM 11-5826-225-35

Remove four screws (20) and four

nuts (17) securing connector (21)

to retaining plate (8).

Remove retaining plate (8).

Loosen setscrews (71) and (75)

on collars (72) and (76), respectively.

Pull out stop hub assembly (57),

along with five stop washers (59,

61, 63, 65, and 67) and five flat

washers (58, 60, 62, 64, and 66),

from the rear of frame (136).

Remove two collars (72 and 76),

flat washer (70), and worm gear

(73).

Loosen the two setscrews (78) in

collar (77), and remove the collar

(77).

Remove dial drum lever (81) from

the frame (136).

Remove spring (55) from the

grooved pin in the frame (136).

Remove detent follower (56) from

the frame (136).

Withdraw switch detent (82) from

the rear of the frame (136).

i. Removal of Lanpholder for Dial Lamps

(DS307, DS308) .

(1) Set the range switch to 190-400.

(2) Loosen two Dzus fasteners (1) located on the rear cover (2), and slide

the rear cover (2) off the control unit.

(3) Remove wire clamp (147), terminal

lug (148), and lockwasher (149) by

removing screw (152).

Note. Terminal stud (150) may be used in

place of screw (152) on some control units.

(4) Remove two screws (34), and remove

lamp bracket (29) from the frame

(136).

(5) Two lamps (27) are removed from

3-6.

a.

lamp bracket (29) by rotating electrical clamp (26) around the tubular

rivet (25).

Reassembly and Lubrication of Control

Unit

General. Lubrication of the control unit

is included in the following reassembly pro3-13
TM 11-5826-225-35

cedures. After lubricating a lubricating a component, wipe

off any excess lubricant with a clean, lint-free

cloth. Refer to figure 5–17 throughout the reassembly of the control unit.

b. Replacement of Range Switch (S304).

Note. If the switch detent (82) and detent follower

(56) are to be replaced along with switch section (84),

start this procedure with (1) below. But if just switch

section (84 ) is to be replaced start this procedure with

(14 ) below.

(1) Apply a small quantity of N H L-L7870 oil to the inner surface of the

bearing located in the lower righthand corner of frame (136), as

viewed from the front.

(2) Insert switch detent (82) through its

bearing from the rear of frame (136).

(3) Place notched end of detent follower

(56) on the grooved pin on frame

(136) with notch opening toward the

edge of frame (136).

(4) With the wheel of detent follower

(56) in a detent of switch detent (82),

connect spring (55) between riveted

end of detent follower (56) and a

grooved pin on frame (136).

(5) Mount dial drum level (81) on a pin

on the rear of frame (136), oriented

so pin (80) protrudes toward the

rear of frame (136). The shaft on

switch detent (82) should protrude

through the closed slot on dial drum

lever (81).

(6) Insert split sleeve bearing (79) into

collar (77), and place them on the

shaft of switch detent (82). Do not

tighten setscrews (78) on collar (77).

(7) Starting with flat washer (58), alternately place five flat washers (58, 60,

62, 64, and 66) with five stop washers

(59, 61, 63, 65, and 67) on the shaft

of stop hub assembly (57).

(8) Place spring tension washer (68) and

flat washer ( (69) on the shaft of stop

huh assembly (37).

(9) Apply a small quantity of MIL-L7870 lubricant to each of the five flat

washers (58, 60, 62, 64, and 66).

(10) Insert the shaft of stop hub assembly

( 57) approximately 1⁄2 inch through.

the bearing located in the lower left

corner of frame (136) as viewed from

the rear.

(11) Place flat washer (70), collar (72),

worm gear (73) with shank toward

the rear of frame (136), bearing

sleeve (74), and collar (76) on the

shaft of stop hub assembly (57) that

is protruding through the bearing on

frame (136).

(12) Continue to insert the shaft of stop

hub assembly (57) through the bearing on frame (136) and through the

shaft of switch detent (82) until stop

h hub assembly is fully seated against

the bearing on frame (136).

(13) Hold collar (72) and worm gear (73)

against the bearing through which the

shaft of stop hub assembly (57) is

inserted and, with stop hub assembly

(57) seated against the bearing,

tighten setscrews (71).

(14) Slide collar (76) and bearing sleeve

( (74) toward the front of frame (136)

until they are against the shaft of

switch detent (82). Tighten two setscrews (75).

(15) Orient switch section (81) so the x

mark near one of the securing holes

is facing toward the front of frame

(136), and is to the right as seen from

the front.

(16) Slide switch section (84) onto the

shaft of switch detent (82). The notch

in the shaft slot of switch section (84)

should be to the left as viewed from

the front.

(17) Mount switch section (84) to the front

of frame (126) with two spacers (83),

two screws (87), two nonmetallic

washers (86), and two lockwashers

(85).

3-14
placed, perform alignment procedures

in paragraph 3-22.

c. Replacement of Gear Train.

(l)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

If the range switch has been removed,

replaced it (b above).

Apply a small quantity of MIL-L7870 oil to the inner surface of the

bearings located at the top and bottom

of frame (136), and to the right as

viewed from the front.

Place thrust washer (51), torsion

spring (50), helical gear (49), helical

spring (48), and flat washer (47)

around gear shank of helical gear assembly (52).

Place the ends of torsion spring (50)

into the retaining holes in helical gear

(49) and helical gear assembly (52).

Squeeze flat washer (47) together

with helical gear assembly (52 ), and

push retaining ring (46) into the

groove around gear shank of helical

gear assembly (52).

Slide collar (44) onto the longer section of shaft on helical gear assembly

(52).

Slide collar (54) on the shorter section of shaft on helical gear assembly

(52).

Orient helical gear assembly (52) so

the shorter section of shaft is pointed

down.

Place helical gear assembly (52),

along with collars (44 and 45), between the two bearings located at the

top and bottom of frame (136), and

to the right as viewed from the front.

Place flat washers (117), spring tension washer (118) and another flat

washer (119) around the shank of

spur gear (120).

Note. The number of flat washers ( 117)

was recorded in the disasembly procedure

of the gear train in paragraph 3–5e.

Insert the shank of spur gear (120)

through the bottom bearing on frame

(136), and slide the shank

gear, 120) over the shorter

helical gear assembly (52).

(12)

(13)

(14)

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

TM 11-5826-225-35

With the shaft of helical gear assembly (52) flush with bottom of recess in

spur gear (120), slide collar (54) over

the end of the shank of spur gear

(120) and tighten two setscrews (53).

Push helical gear assembly (52) downward until helical gear (49) is the only

gear engaged with worm gear (73).

Rotate spur gear (120) eight teeth

clockwise as viewed from the bottom

of frame (136).

Push helical gear assembly (52) upward until helical gear (49) and the

gear on helical gear assembly (52)

are both engaged with worm gear

(73).

Note. In the following procedures, do not

allow helical gear (49) or the gear on helical

gear assembly (52) to become disengaged

with worm gear (73). Disengagement will

cause loss of spring loading between helical

gear (49) and helical gear assembly (52 ).

If disengagement occurs, repeat (13), (14)

and (16) above to restore spring loading.

Insert shank of spur gear (43)

through the top bearing on frame

(136), and slide the shank of spur

gear (43) over the longer shaft of

helical gear assembly (52).

With the shaft of helical gear assembly (52) flush with the bottom of the

recess in spur gear (43), slide collar

(45) over the shank of spur gear (43)

and tighten two setscrews (44).

Loosen two setscrews (53) and slide

collar (54) down until it is against

the bearing in the bottom of frame

(136).

Apply blue varnish to the threads of

two setscrews (53), and tighten two

setscrews (53).

Loosen two setscrews (44) and slide

collar (45) up until it is against the

bearing at the top of frame (136).

Apply blue varnish to the threads of

two setscrews (44), and tighten.

If there are no other parts to be replaced, perform alignment procedures

in paragraph 3-22.

3-15
TM 11-5826-225-35

d. Reclacement of Dial Drum.

(1)

(2)

(3)

(4)

(5)

(6)

(7)

(8)

(9)

(l0)

(11)

(12)

(13)

If the gear train is removed, replace

it (c above).

Apply a small quantity of MIL-L7870 oil to the inner surface of the

bearings located at the top and bottom, and in the center, of frame

(136).

Place load spring (31) around the

shank of the gear on spur gear assembly (30) .

Slide spur gear (32) onto the shank of

the gear on spur gear assembly (30).

Place the ends of load spring (31) in

the retaining holes in spur gear (32)

and the gear on spur gear assembly

(30).

Place retaining ring (33) in the slot

around the shaft of spur gear assembly (30).

Loosen two setscrews (78) on collar

(77) to allow the lever of dial drum

lever (81) to be pushed to the bottom

of frame (136).

Insert the shaft of spur gear assembly (30) through the top of the bearing located at the top and center of

frame (136).

Place bearing sleeve (38) inside collar (37) and slide them over the shaft

of spur gear assembly (30).

Place -helical spring (40) around the

shaft of spur gear assembly (30).

Insert the shaft of spur gear assembly (30) into dial drum (41), and set

dial drum (41) on top of the lever of

dial drum lever (81).

Rotate collar (77) until dial drum

lever (81) raises dial drum (41) approximately 1⁄4 inch from the top of

frame (136).

Tighten one of the setscrews (78) on

collar (77).

(14) Place washer (42) on the end of the

shaft on spur gear assembly (30),

and insert the end of the shaft into

(15)

(16)

(17)

(18)

(19)

(20)

(21)

(22)

(23)

(24)

the bearing located at the bottom and

center of frame (36).

Lower spur g-ear assembly (30) until

just one spur gear (32) is engaged

with spur gear (43).

As viewed from the top, rotate dial

drum (41) clockwise until the gear on

spur gear assembly (30) rotates clockwise 11 teeth.

Lower spur gear assembly (30) until

the gear on spur gear assembly (30).

engages with spur gear (43).

Loosen setscrew (78) on collar (77)

and let dial drum lever (81) lower

dial drum (41) to the bottom of frame

(136).

Place the bottom of helical spring

(40) over the center post in the bottom of dial drum (42).

Insert the hooked end of helical spring

(40) into the hole in collar (37).

As viewed from the top, rotate collar

(37) clockwise until one revolution

of tension is placed on helical spring

(40).

Apply blue varnish to the threads of

two setscrews (35).

Tighten two setscrews (35).

If there are no other parts to be replaced, perform alignment procedures

in paragraph 3–22.

e. Replacement of Tuning Synchro (B301).

 (1)

(2)

(3)

(4)

(5)

If the dial drum is removed, replace

it (d above).

Use three screws (155) and three

lockwashers (154) to loosely secure

three rim-clenching clamps (153) to

frame (136).

Insert the shaft of transmitter synchro (156) through the mounting hole

in frame (136), and secure transmitter synchro (156) to frame (136) with

three rim-clenching clamps (153),

Place load spring (122) around the

shank of spur gear (123).

Slide spur gear (121) over the shank

of spur gear (123), and insert the

3-16
(6)

(7)

(8)

(9)

(lo)

ends of load spring (122) into the

retaining holes in spur gears (121 and

123) .

Place collar (128) on the shank of

spur gear (123), and tighten two setscrews (127) only as much as necessary to retain collar (128) on the

the shank of spur gear (123).

With collar (128) towards frame

(136), slide the two spur gears (121

and 123) onto the shaft of transmitter synchro (156) only as far as necessary to engage spur gear (121) with

spur gear (120).

As viewed from the bottom of frame

(136), rotate spur gear (123) eleven

teeth clockwise and engage spur gear

(123) with spur gear (120).

Tighten two setscrews (127).

If there are not other parts to be replaced, perform alignment procedures

in paragraph 3-22.

f. Replacement of Function Switch (S302).

(1)

(2)

(3)

(4)

(5)

(6)

Orient switch section (139) so the

side with the X mark is facing the

same direction as the front of frame

(136), and the X mark is towards the

top. The notch in the shaft slot of

switch section (139) should be at the

left as viewed from the front.

Orient switch section (140) the same

as switch section (139) is oriented.

Use two spacers (137) to separate

switch sections (139, 140) from each

other, and two spacers (138) to separate switch sections (139 and 140)

from frame (136).

Use two screws (142), two lockwashers (143), and two nonmetalli c

washers (144) to secure switch sections (139 and 140) and spacers (137

and 138) to frame (136).

Apply a small amount of MIL-L7870 oil to the inner surface of the

bearing located on the lower left edge

of frame (136) as viewed from the

front.

Insert the shaft of switch detent

(7)

(8)

(9)

(lo)

(11)

(12)

TM 11-5826-225-35

(124) through the front of the bearing located on the lower left edge of

frame (136) as viewed from the

front.

Continue to insert the shaft of switch

detent (124) through the shaft slots

of switch sections (139 and 140). Seat

switch detent (124) against the bearing on frame (136).

Place the notch of detent follower

(125) on the lower left-hand grooved

pin on frame (136) with notch opening facing left, as viewed from the

front.

With the wheel of detent follower

(125) in a detent of switch detent

(124), connect spring (126) between

rivet of detent follower (125) and the

grooved pin on the front of frame

(136).

Slide spring tension washer (145)

over the shaft of spur gear assembly

(146).

Insert the shaft of spur gear assembly

(146) as far as possible through the

bearing and the shaft of switch detent

(124) from the rear of frame (136).

Place retaining ring (141) in the slot

around the shaft of spur gear assembly (146).

g. Replacement of Attenuator (R301).

(1)

(2)

(3)

(4)

(5)

If the function switch is removed, replace it (f above).

If variable attenuator (166) is not

connected to leads, make the connections now.

Place lockwasher (165) on mounting

shank of variable attenuator (166),

and insert the shank of variable attenuator (166) through the mounting

hole in frame (136).

Secure variable attenuator (166) to

frame (136) with lockwasher (164)

and nut ( 163).

Place crown gear (162) on the shaft

of variable attenuator (166) so crown

gear (162) meshes with the spur gear

on spur gear assembly (146).

3–17
TM 11-5826-225-35

(1)

(2)

(3)

(4)

(5)

If rotary switch (151) is not wired,

connect the leads now.

Insert the shank of rotary switch

(151) into the hole in the upper left

corner of frame (136).

Secure rotary switch (151) to frame

(136) with lockwasher (129) and nut

(130).

Orient terminal board (157) so resistor R306 (4,700 ohms) is on top.

Use two nuts (160), two lockwashers

(159), and two flat washers (158) to

secure terminal board (157) to rotary

switch (151).

i. Replacement of Rear Retaining Plate.

(1)

(2)

(3)

(4)

Slide spacer plate (19) around rear

portion of connector (21). Align the

mounting holes on spacer plate (19)

with the mounting holes on connector (21).

Fasten connector (21) and spacer

plate (19) to retaining plate (8) with

four screws (20) and four nuts (17).

Secure fixed resistor (12) and solder

lug (9) to retaining plate (8) with

screw (7).

Secure retaining plate (8) to frame

(136) using three screws (5) and

three lockwashers (6). Use care to

avoid pinching or straining the leads.

j. Replacement of Front Panel.

(1)

(2)

(3)

3–l8

Secure dial mask (135) to the front

of frame (136) with two screws

(132), two lockwashers (131), and

two flat washers (134).

Fasten ammeter (90) to f rent subpanel assembly (88) using two nuts

(89) and two screws (91).

Place f rent subpanel assembly (88)

over the shafts protruding from the

front of frame (136), and insert

toggle switch (143) through the hole

in front subpanel assembly (88).

(4)

(5)

(6)

(7)

(8)

(9)

(10)

(11)

(12)

(13)

(14)

(15)

(16)

(17)

Secure toggle switch (133) to front

subpanel assembly (88) Using lockwasher (115) and nut (114).

If ammeter (90) is not wired, connect

leads now.

Pass the two panel lamp leads

through the hole in the lower left

corner of frame (136) and through

the slot in front subpanel assembly

(88).

Fasten front subpanel assembly (88)

to frame (136) using four screws

(112) and four lockwashers (113).

Solder the two panel lamp leads to the

two terminals on panel light assembly

(92).

Fasten panel light assembly (92) to

front panel (93) using two screws

(108).

Place front panel (93) over the shafts

protruding from the front of flame

(136), and secure front panel (93)

to frame (136) using two screws

(106) and two rubber washers (107).

Place function knob (105) on its

shaft, leaving a small gap between

function knob (105) and front panel

(93). Rotate function knob (105)

fully counterclockwise. Function knob

(105) should point to OFF.

Tighten setscrew (104).

Place range knob (94) on its shaft.

leaving a small gap between range

knob (94) and front panel (93). Rotate range knob (94) fully counterclockwise. Range knob (94) should

point to 190-400.

Tighten setscre (98).

Place flat washer (103) and GAIN

knob (102) on shaft protruding from

function knob (105). Leave a small

gap between function knob (105) and

GAIN knob (102) in addition to the

gap caused by flat washer (103).

Tighten t two setscrews (101).

Place flat washer (95) and TUNE

knob (97) on shaft protruding from

range knob (94). Leave a small gap

between range knob (94) and TUNE
(18)

(19)

(20)

knob (97) in addition to the gap

caused by flat washer (96).

Tighten two setscrews (96).

Place loop knob (99) on its shaft and

align loop knob (99) so it is in a

vertical position.

Tighten two setscrews (100).

k. Replacement of Rear Cover.

(1) Perform alignment procedures contained in paragraph 3-22.

Section II.

3-8. General

Alignment and adjustment procedures for Radio

Receiver R-1391/ARN-83 are given in paragraphs

3-10 through 3-20. Voltage and frequency adjustment for Inverter, Power, Static CV-2128/ARN-83

is given in paragraphs 3-21 and 3-21.1. Alignment

for Direction Finder Control C-6899/ARN-83 is

given in paragraph 3-22. Antenna AS-1863/ARN83 does not require alignment. The test equipment

and additional equipment required for alignment

and adjustment are listed in paragraph 3-9.

3-9. Teat Equipment and Additional Equip

ment Required for Alignment

a. Test Equipment.

(1)

(2)

(3)

(4)

(5)

Test Set, Direction Finder Set AN/

ARM-93.

Signal Generator AN/URM-25( ),

two each.

Output Meter TS-585/U.

Multimeter ME-26/U.

Tuning capacitor test cable (fig. 8-45)

consisting of the following:

(a) Connector (Pi), Cannon DPXE.

45-34P-0201.

(b) Connector (P2), Cannon DPX 45

33S.

(c) Wire, #22 AWG, stranded, insulated (7 feet),

(6) Frequency Meter AN/USM-26( ).

(7) Oscilloscope AN/USM-140.

b. Additional Equipment.

(1) Dc power supply, 27.5 volts.

(2)

(3)

TM 11-5826-225-3S

Carefully slide rear cover (2) over

the rear of the control unit.

Secure rear cover (2) to the control

unit by tightening two Dzus fasteners

(l).

3-7. Periodic lubrication

No periodic lubrication is

disassembly intervals.

ALIGNMENT

required between

(2) Headset HS-33, or equivalent.

(3) Stopwatch.

(4) RF balance teat jig (fig. 8-4), consisting of the following:

(a)

(b)

(c)

(d)

(e)

Connector, Bendix PTOGA-10-6S

(PI).

Two connectors, UG-912A/U (P2

P3).

Two resistors, 1/2 watt, 51 ohms,

±1 percent, type RN65D51R1F

(Rl, R2).

Two capacitors, 500 volts, 10 μμf,

±10 percent, type CM05C100K09

(C1, C2).

Capacitor, 500 volts, 240 μμf, ±6

percent, type CM05F241J03. (C3).

3-10. Adjustment of Tuning Servo Tachometer Feedback

a. Remove the cover from the gear train

assembly of the receiver.

b. Connect the equipment as shown in figure

2-2. It is not necessary to connect the signal

generator, audio output meter, or headset.

c. se t

(1)

(2)

(3)

the switches on the test set as follows:

DC POWER switch to ON.

RECEIVER-CONTROL switch to

RECEIVER,

GONIO DRIVE switch to ON.

d. Set the switches on the control

follows :

(1) Function switch to ANT.

unit as

Change 5 3-19
TM 11-5826-225-35

(2) Range switch to 190-400.

(3) TUNE control for 300 kc on the FREQUENCY indicator.

(4) BFO-OFF switch to OFF.

.

e. Loosen the locknut on resistor Rlll (fig.

2-8) on the receiver, and rotate Rlll fully

clockwise.

f. Rotate the TUNE control on the control

unit while observing the operation of the gear

train connected to the sections of capacitor

cl (fig. 2-8).

g. Adjust R111 counterclockwise until the

gear train overshoots the new proper position

and reverses its direction to correct for the

overshoot. Adjust R111 until this effect is

small but still noticeable.

h. Tighten the locknut on R111, and replace

the cover on the gear train assembly.

3-11. Function and Range Switch Centering

Adjustments

a. Obtain access to the rear of the gear train

assembly of the receiver as follows:

(1) Remove the two outside, rearmost

screws on the top of the chassis.

(2) Remove the two rearmost screws on

the bottom of the chassis.

(3) Swing out the rear of the chassis to

the right, as viewed from the front

of the receiver.

b. Connect the equipment as shown in figure

2-2. It is not necessary to connect the signal

generator, audio output meter, or headset.

c. Set the switches on the control unit as

follows :

(1) Function switch to ANT.

(2) Range switch to 400-350.

Figure 3-3. RF balance adjustment test setup.

3-20 Change 1
TM 11-5826-225-35

(3) BFO–OFF switch to OFF.

d. Set the switches on the test set as follows:

(1)

(2)

(3)

e. Set

DC POWER switch to ON,

RECEIVER-CONTROL switch to

RECEIVER.

GONIO DRIVE switch to ON.

the function switch on the control

unit to LOOP. Then return the switch to ANT.

f. Note the position of the switch rotors

which are connected mechanically to the gear

train subassembly. All switch rotors should be

Figure 3-4. RF balance test jig, schematic

diagram.

positioned as shown on the schematic diagram

of the receiver (fig. 5–10 or 5–10.1).

g. If the rotors are not positioned as in f

above, loosen screws (33, fig. 5–16) and rotate

switch wafer (23) until tabs are centered.

Then retighten screws {33).

3-12. Adjustment and Synchronization of

Tuning Capacitor

a. Loosen setscrews (68, fig. 5–16) on collar

(69 ) of gear train assembly in the receiver.

b. Swing out the rear of the chassis (para

3-11a).

c. Connect the input terminal of the vtvm

to S3 of B1 (fig. 2–7), Connect the ground

terminal of the vtvm to S1 of B1.

Figure 3-5. Schematic diagram of tuning

capacitor test cable.

Figure 3–6. Block diagram of adjustment and synchronization of tuning capacitor setup.

Change 1 3-21
TM 11-5826-225-35

d. Connect the equipment as shown in figure

3-6. A schematic diagram of the tuning capacitor test cable is shown in figure 3–5. *

e. Set the control unit range switch to 850–

1750.

f. Adjust the control unit TUNE control so

that the hairline of the FREQUENCY indicator bisects the small circle located between

1,400 and 1,500 kc.

g. Set the control unit switches as follows:

(1) Function switch to ANT.

(2) BFO-OFF switch to OFF.

k. Set the test set switches as follows:

(1) RECEIVER-CONTROL switch to

RECEIVER.

(2) DC POWER switch to ON.

i. Rock the control unit TUNE control back

and forth across the small circle on the FREQUENCY dial and adjust it for a null (minimum ) indication on the vtvm.

j. Manually rotate the shaft which drives

capacitor Cl (fig. 2-8) until the rotor plates

of section Cl–E (nearest the gear train) are

fully meshed with the stator plates. The plates

must be exactly meshed, with the tops of the

rotor plates exactly in line with the tops of

the stator plates.

k. Tighten the setscrews (68, fig. 5-16)

on collar (69). Be careful that the split gears

on the capacitor shaft do not become unmeshed and lose- their spring loading.

CAUTION

After tightening the setscrews (k

above), do not move the control

TUNE control until the tuning capacitor test jig has been removed.

l. Throw the test set DC POWER switch

to OFF.

m. Disconnect the vtvm.

n. Remove the tuning capacitor test jig

from the equipment setup, and connect P2 of

the test set directly to J3 of the receiver.

o. Throw the test set DC POWER switch

to ON.

p. Slowly rotate the control unit TUNE control in a clockwise direction. The rotor plates

of capacitor Cl should rotate out of mesh with

the stator plates.

3–13. Local Oscillator Alignment

a. Connect the equipment as shown in figure

2–2. It is necessary to connect the audio output

meter. .

b. Loosen the locknuts on resistors R82,

R90, and R131 (fig. 2–8) on the receiver, and

adjust each resistor fully clockwise.

c. Adjust R136 fully clockwise (fig. 2-8),

and then adjust R136 five turns counterclockwise.

d. Set the switches on the control unit as

follows :

(1) BFO-OFF switch to BFO.

(2) Function switch to ANT.

e. Set the switches on the test set as follows:

(1) DC POWER switch to ON.

(2) RECEIVER-CONTROL switch to

RECEIVER.

(3) GONIO DRIVE switch to ON.

f. Set the 150 PF-270PF switch on the sense

antenna adapter to 150 PF.

g. Set the range switch on the control unit

to 190–400, and adjust the TUNE control on

the control unit for 390 kc on the FREQUENCY indicator.

h. Set the frequency of the signal generator

to 390 kc, plus or minus 0.1 kc.

i. Modulate the signal generator output 30.

percent with 400 cps. Maintain this modulation

throughout the procedures.

j. Adjust C36 (fig. 2–16 or 2–16.1) until a

zero beat is heard in the headset.

k. Adjust the TUNE control on the control

unit for 200 kc on the FREQUENCY indicator,

1. Set the signal generator to 200 kc, plus

or minus 0.1 kc.

m. Listen for a zero beat in the headset

while adjusting the TUNE control on the con3-22 Change 1
trol unit to 1.5 kc on either side of 200 kc

(198.5 kc to 201.5 kc). If a zero beat is not

heard, remove the cover of L3 (fig. 2-16 or

2–16.1) and adjust L3 for a zero beat at 200 kc.

n. Repeat g through m above until a zero

beat is heard at both 390 kc and 200 kc.

o. Temporarily replace the cover of L13 (do

not solder) and repeat g through m above for

the zero beats.

p. Set the range switch on the control unit

to 400-850, and adjust the TUNE control on

the control unit for 800 kc.

q. Set the signal generator to 800 kc, plus

or minus 0.1 kc.

r. Adjust C40 (fig. 2-16 or 2-16.1) for a

zero beat in the headset.

s. Adjust the TUNE control on the control

unit for 420 kc.

t. Set the signal generator to 420 kc, plus

or minus 0.1 kc.

u. Listen for a zero beat in the headset while

adjusting the TUNE control on the control

unit to 2.5 kc on either side of 420 kc (417.5

kc to 422.5 kc). If a zero beat is not heard

remove the cover of L4 (fig. 2-16 or 2-16.1)

and adjust L4 for a zero beat at 420 kc.

v. Repeat p through u above until a zero beat

is heard at both 800 kc and 420 kc,

w. Temporarily replace the cover of L4 (do

not solder). and repeat p through u above for

the zero beats.

x. Set the range switch on the control unit to

850–1750, and adjust the TUNE control on the

control unit for 1700 kc.

y. Set the signal generator to 1700 kc plus

or minus 0.1 kc.

z. Adjust the TUNE control on the control

unit for 900 kc.

aa. Adjust C44 (fig. 2–16 or 2-16.1) for

a zero beat in the headset.

ab. Set the signal

or minus 0.1 kc.

generator to 900 kc, plus

TM 11-5826-225-3S

ac. Listen for a zero beat in the headset

while adjusting the TUNE control on the control unit to 5.0 kc either side of 900 kc (895

kc to 905 kc), If a zero beat is not heard,

remove the cover of L5 (fig. 2-16 or 2-16.1)

and adjust L5 for a zero beat at 900 kc.

ad. Repeat x through ac above until a zero

beat is heard at both 1700 kc and 900 kc.

ae. Temporarily replace the cover of L5 (do

not solder) and repeat x through ac above for

the zero beats.

af. Solder the covers in place on L3, L4, and

L5.

3-14. RF Alignment

a. Connect the equipment as shown in figure

2-2. -

b. Perform the procedures in paragraph 3-

13b, c, d, and e.

c. Set the 150PF-270PF switch on the sense

antenna adapter to 150PF.

d. Set the range switch on the control unit

to 190-400, and adjust the TUNE control on

the control unit for 390 kc on the FREQUENCY indicator.

e. Modulate the signal generator output 30

percent with 400 cps. Maintain this modulation

unless instructed otherwise.

f. Set the frequency of the signal generator

to 390 kc (the same as the receiver setting)

as determined by a zero beat in the headset.

g. Set the BFO-OFF switch on the control

unit to OFF.

h. Disconnect the headset from the test

set.

i. Adjust the GAIN control on the control

unit to approximately three-fourths of the fully

clockwise position (maximum gain).

j. Adjust the output of the signal generator

for 20 milliwatts (row) on

meter.

NOTE

Maximum sharpness of

the audio output

tuning indiChange 1 3-23
TM 11-5826-225-35

cation is achieved by maintaining

approximately 20-mw output on the

audio output meter.

k. Adjust C16 (fig. 2-12 or 2-12.1), C23,

and C26 (fig. 2-13 or 2-13.1), in that order,

for maximum indication on the audio output

meter.

l. Check that the screwdriver slots in C16,

C23, and C26 are not parallel to the front-torear axis of the receiver. If any of the screwdriver slots lie parallel to this plane, the corresponding transformer for that capacitor (T104

for C16, T107 for C23, and T10 for C26) must

be adjusted. If T104 (fig. 2–12 or 2-12.1),

T107, or T10 (fig. 2–13 or 2-18.1) must be

adjusted, proceed as follows:

(1) Reconnect the headset to the test set.

(2) Set the BFO-OFF switch on the control unit to BFO.

(3) Adjust the TUNE control on the control unit for 200 kc.

(4) Set the signal generator to 200 kc

as determined by a zero beat in the

(5)

(6)

(7)

(8)

(9)

(l0)

(11)

headset.

Set the BFO-OFF switch on the control unit to OFF.

Disconnect the headset.

Unsolder and remove the cover of

the transformer to be adjusted (T104,

T107, or T10).

Adjust the output of the signal generator for 2 mw on the audio’ output

meter.

Adjust the transformer T107 above

for maximum output on the audio

output meter.

Replace and resolder the cover of

the transformer.

Repeak capacitors C16, C23, and C26

at 390 kc (d through k and (1)

through ( (10) above).

m. Repeat the procedures in d through l

above for the capacitors (figs. 2-12 or 2–12.1,

and fig. 2–13 or 2–13.1) and frequency settings

listed in the chart below. If necessary, adjust

the corresponding transformers (figs. 2-12 or

2-12.1 and 2-13 or 2-13.1). Always repeak

the capacitors if the corresponding transformers require adjustment. Disconnect the headset from the test set when observing the audio

output meter.

Capacitor adjustment Capacitor Coil l tjlubrwlt frequency setting Coil frequency setting

C17 800 T105 420

C24 800 T108 420

C27 800 T11 420

C18 1700 T106 900

C25 1700 T109 900

C28 1700 T12 900

3-15. RF Balance Adjustment

a. Connect the equipment as shown in figure

3-3. The schematic of the test jig is shown in

figure 3-4.

b. Set the switches on the control

follows :

(1) BFO-OFF switch to OFF.

(2) Function switch to ANT.

c. Set the switches on the test set as

(1) DC POWER switch to ON.

unit as

follows :

(2) RECEIVER-CONTROL switch to

RECEIVER.

(3) GONIO DRIVE switch to ON.

d. Set the range switch on the control unit

to 190-400, and adjust the TUNE control on

the control unit for 400 kHz on the FREQUENCY

indicator.

e. Adjust the output of signal generator A

to zero.

f. Set the frequency of signal generator B

to 400 kc and the output to 100 microvolt,

modulated 30 percent with 400 cps. Adjust

the frequency of the signal generator for maximum indication on the audio output meter.

g. Adjust the GAIN control on the control

unit for 20 mw on the audio output meter.

h. Set the frequency of signal generator A

to 560 kc.

3-24 Change 5
TM 11-5826-225-35

i. Set the frequency of signal generator B

to 960 kc.

j . Adjust R136 full counterclockwise. Adjust the

output of both signal generators to 100000

microvolt.

k. Adjust the frequency of signal generator

A for maximum indication on the audio output

meter.

NOTE

Do not change the setting of the

GAIN control on the control unit.

1. Adjust the outputs (not the frequency)

of both signal generators to equal levels to

produce a 20-mw audio output on the audio

output meter. The output of the two signal

generators must be the same for this setting.

m. Adjust R136 (fig. 2-8) fully counterclockwise. Then adjust R136 five turns clockwise,

n. If necessary, adjust the outputs of both

signal generators equally to indicate between

10 and 20 mw on the audio output meter.

o. Adjust R136 for minimum indication on

the audio output meter.

NOTE

Balance (minimum audio output)

should occur within three turns of

the setting in m above.

3-16. First RF Amplifier Alignment

a. Connect the equipment as shown in figure

2-2.

b. Set the switches on the control unit as

follows :

(1) BFO-OFF switch to OFF.

(2) Function switch to ANT.

c. Set the switches on the test set as follows:

(1) DC POWER switch to ON.

(2) RECEIVER-CONTROL switch to

RECEIVER.

(3) GONIO DRIVE switch to ON.

d. Set the range switch on the control unit

to 190-400, and adjust the TUNE control on

the control unit to 390 kc.

e. Modulate the signal generator 80 percent

with 400 cps.

f. Set the frequency of the signal generator

to 390 kc (the same as the receiver) as determined by a zero beat in the headset.

g. Disconnect the headset,

h. Adjust the loop simulator control on the

test set so that the LOOP SIMULATOR indicator on the test set indicates 90° from the

indication on the BEARING INDICATOR on

the test set. Slightly adjust the loop simulator

control for a maximum indication on the tuning meter on the control unit, Peaking of

the tuning meter indicates maximum signal

pickup.

i. Set the BFO-OFF switch on the control

unit to OFF.

j. Set the GAIN control on the control unit

to approximately three-fourths of the fully

clockwise position.

k. Adjust the output of the signal generator

for 20 mw on the audio output meter. Maintain

this indication approximately throughout. the

procedures.

l. Unsolder and remove the cover of T1 (fig.

2-9 or 2-9.1).

m. Set the TUNE control on the control unit

for 200 kc.

n. Set the frequency of the signal generator

to 200 kc. Vary the frequency slightly in the

vicinity of 200 kc, and note the maximum indication in db on the audio output meter.

o. Reconnect the headset to the test set, and

adjust the frequency of the signal generator

to 200 kc as determined by a zero beat in the

headset.

p. Disconnect the headset, and note the indication in db on the audio output meter. This

indication must be within 1 db of the indication noted in n above. If the difference is more

than 1 db, proceed as follows:

(1) Remove the cover of T1 (fig. 2-9 or

2-9.1).

(2) Adjust the output of the signal genChange 5 3-25
TM 11-5826-225-35

(8)

(4)

(6)

(6)

erator for approximately 20 mw on

the audio output meter.

Adjust T1 for a maximum indication

on the audio output meter.

Repeat d through p above until no

further adjustment is required.

Temporarily replace the cover of T1

(do not solder).

Repeak C2 at 890 kc.

q. Check that the screwdriver slot in C2

is not parallel to the front-to-rear axis of the

receiver. If the screwdriver slot is parallel to

this plane, readjust T1 at 200 kc. Then repeak

C2 at 890 kc.

r. Repeat the procedures in b through q above

for the capacitors (fig. 2-9 or 2-9.1) listed in

the chart below. If necessary, adjust the corresponding transformer (fig. 2-9 or 2-9.1) for

each capacitor according to the requirement

of p above. Always disconnect the headset

when observing the audio output meter.

C3

C4

420

900

a. Connect the equipment as shown

2-2.

b. Set the switches. on the control

follows :

(1) BFO-OFF switch to BFO.

(2) Function switch to ANT.

in figure

units as

(3) GAIN control fully clockwise.

c. Set the switches on the test set as follows:

(1) DC POWER switch to ON.

(2) RECEIVER-CONTROL switch to

RECEIVER.

(3) GONIO DRIVE switch to ON.

d. Set the range switch on the control unit

to 190-400, and adjust the TUNE control on

the control unit to 200 kc.

e. Modulate the signal generator output 30

“percent with 400 cps, and adjust the output

for 1000 microvolt.

f. Set the frequency of the signal generator

to 200 kc (the same as the receiver) as determined by a zero beat in the headset.

g. Disconnect the headset.

h. Set the BFO-OFF switch on the control

unit to OFF.

i. Adjust R82 (fig. 2-8) for 100 mw on the

audio output meter. Then tighten the locknut

on R82.

j. Adjust the output of the signal generator

to 20 microvolt. Keep the modulation at 30

percent.

k. Adjust R90 (fig. 2-8) for 80 mw on the

audio output meter. Then tighten the locknut

on R90.

3-17.1 11 O-Hz Oscillator Frequency

a.

2. It is not necessary to connect the ‘signal

generator, audio output meter, or headset.

b. Set the switches on the control unit as

follows:

(1) BFO-OFF switch to OFF,

(2) Function switch to ADF.

c. Set the switches on the test set

(1) DC POWER switch to OFF.

as follows:

(2) GONIO DRIVE switch to OFF.

(3) RECEIVER-CONTROI, switch to

RECEIVER.

d. Refer to figure 2-7. Unsolder and disconnect

the negative lead of capacitor C153.

e. Select a capacitor combination listed in the

chart below. Connect the capacitor combination

between the positive leads of capacitors C151 and

C153.

3-26 Change 5
Capacitor

combinations

(μF)

47 and 47

17 and 56

47 and 68

56 and 56

56 and 68

47 and 100

68 and 68

56 and 100

68 and 100

100 and 100

Total series

capacitance

(μF)

23.5

‘25.6

27.8

28.0

30.7

32.0

34.0

46.0

40.5

50.0

f. Set test set DC POWER switch to ON.

g. Refer to figure 2-6. Connect frequency meter

to positive lead of capacitor C68 and measure the

frequency out of the 110-HZ oscillator. If the frequency is lower than 104 Hz, a capacitor combination with a lower total capacitance will be required. If the frequency is above 116 Hz, a

capacitor combination with a higher total

capacitance will be required. Several attempts

may be necessary to determine which capacitor

combination is capable of providing 110 ±6-Hz

operation from the 110-HZ oscillator.

h. After the proper capacitor combination is

determined, set test set DC POWER switch to

OFF. Unsolder and remove old capacitors C151

and C153 and replace with selected values.

3-17.2. 90-Degree Phase Shift

Adjustment

NOTE

Capacitor C82 is selected from 0.16 μF,

0.34 μF, 0.50 μF, or 0.75 μF to obtain a

90-degree phase shift between the 110-

Hz oscillator and the loop servo

amplifier. This selection is necessary

due to variations in the components of

the loop servo-amplifier circuitry.

TM 11-5826-225-35

a. Connect the equipment as shown in figure 2-

2. It is not necessary to connect the audio output

meter or headset.

b. Set the switches on the control unit as follows:

(1) BFO-OFF switch to OFF.

(2) Function switch to ADF.

c. Set the switches on the test set as follows:

(1)

(2)

(3)

DC POWER switch to OFF.

RECEIVER-CONTROL switch to

RECEIVER.

GONIO DRIVE switch to ON.

d. Set the range switch on the control unit to

190-400, and adjust the TUNE control on the control unit to 200 kHz.

e. Adjust the frequency of the signal generator

to 200 kHz, unmodulated, at an output level of

1000 microvolt.

f. Refer to figure 2-6. Connect the horizontal input of the oscilloscope to the positive lead of

capacitor C68 and the vertical input to the collector of transistor Q24.

g. Adjust the vertical and horizontal sweep of

the oscilloscope for the same amplitude.

h. Refer to figure 2-7. Unsolder and disconnect

the negative lead of capacitor C82.

i. Select a value for C82 (0.16 μF, 0.35 μF, 0.50

μF, or 0.75 μF) and connect between the positive

lead of capacitor C82 and ground.

j. Set test set DC POWER switch to ON.

Observe the Lissajous pattern on the oscilloscope.

k. Repeat steps h through j to select a value of

C82 that will provide the best circular Lissajous

pattern on the oscilloscope.

l. After the proper capacitor value is determined, set the test set DC POWER switch to OFF.

Unsolder and remove old capacitor C82 and

replace with new value.

Change 5 3-27
TM 11-5826-225-35

3-18. Adjustment and Synchronization of

Resolver Servosystem

a. Connect the equipment as shown in figure

2-2.

b. Set the control unit switches as follows:

(1) BFO-OFF switch to BFO.

(2) Function switch to ADF.

(3) GAIN control fully clockwise.

c. Set the test set switches as follows:

(1) RECEIVER-CONTROL switch to

RECEIVER.

(2) GONIO DRIVE switch to ON.

(3) DC POWER switch to ON.

d. Set the control unit range switch to 190-

400, and adjust the control unit TUNE control

to 990 kc on the FREQUENCY indicator.

e. Set the frequency of the signal generator

to 890 kc, unmodulated, at an output level of

1,000 microvolt.

f. Adjust the frequency of the signal generator for a zero beat in the headset. Remove

the headset from the test set.

g. Set the BFO-OFF switch to OFF.

h. Set the LOOP SIMULATOR to N

(zero 0,.

i. Remove the two outside, rearmost screws

on the top of the chassis; remove the two

rearmost screws on the bottom of the chassis,

and swing out the rear of the chassis.

j. Loosen the three screws (51, fig. 5-16)

just enough to rotate the body of B4 (60).

k. Rotate the body of B4 until the test set

BEARING INDICATOR indicates N (zero °).

l. Set the control unit function switch to

LOOP.

m. Rotate the gears (94 and 96) on B3

(110) for a maximum indication on the output

meter,

n. Rotate the body of B4 until the test set

BEARING INDICATOR again indicates N

(zero °).

o. Tighten the three screws (51) and secure

the hinged portion of the receiver.

3-19. Servo Balance Adjustment

a. Connect the equipment as shown in figure

2-2. It is not necessary to connect the signal

generator, audio output meter, or headset.

b. Set the switches on the control unit as

follows :

(1) BFO-OFF switch to BFO.

(2) Function switch to ADF.

(3) GAIN control fully clockwise.

c. Set the switches on the test set as follows:

(1) DC POWER switch to ON.

(2) RECEIVER-CONTROL switch to

RECEIVER.

(3) GONIO DRIVE switch to ON.

d. Set the range switch on the control unit

to 190-400 and adjust the TUNE control on

the control unit to 300 kc on the FREQUENCY indicator.

e. Adjust R10 (fig. 2-8) so that the speed

of rotation of the BEARING INDICATOR

on the test set does not exceed 7200 in 2

minutes.

f. Tighten the locknut of R10.

3-19.1 Slow Slew Speed Adjustment

NOTE

Resistor R133 is selected from 1500,

1800, 2200, 2700, or 3900 ohms to obtain

the proper slow slew speed of the loop

antenna. This selection is necessary due

to variations in the components of the

loop servo-amplifier circuitry

a. Connect the equipment as shown in figure 2-

2. It is not necessary to connect the signal

generator, audio output meter, or headset.

b. Set the switches on the control unit as

follows:

(1) BFO-OFF switch to OFF.

(2) Function switch to LOOP.

c. Set the test set switches as follows:

(1) DC POWER switch to OFF,

3-28 Change 5
TM 11-5826-225-35

(2) GONIO DRIVE switch to ON.

d. Refer to figure 2-7 and note connections for

resistor R133. Unsolder and disconnect both leads

of R133.

e. Select a value for resistor R133 (1500, 1800,

2200, 2700, or 3900 ohms) and connect to terminals

noted in step d.

f. Set the test set DC POWER switch to ON and

the control unit LOOP L-R switch to the first detent toward R.

g. Record the time required for the test set

BEARING INDICATOR to rotate 180 degrees

clockwise.

h. Repeat steps e through g to select a value for

R133 that will provide a slow slew speed of 24 to 36

seconds for a 180-degree clockwise rotation.

i. After the proper resistor value is determined,

set the test set DC POWER switch to OFF.

Replace R133 with new value.

3-20. Adjustment of Adf Hunt Control

a. Connect the equipment as shown in figure

2-2. It is not necessary to connect the audio

output meter.

b. Set

follows :

(1)

(2)

(8)

c. Set

(1)

(2)

(3)

the switches on the control unit as

BFO-OFF switches to BFO.

Function switch to ADF.

GAIN control fully clockwise.

the switches on the test set as follows:

DC POWER switch to ON.

RECEIVER-CONTROL switch to

RECEIVER.

GONIO DRIVE switch to ON.

d. Set the 150PF-270PF switch on the

sense antenna adapter to 150PF.

e. Set the range switch on the control unit

to 190-400, and adjust the TUNE control on

the control unit for 200 kc on the FREQUENCY indicator.

f. Adjust the output of the signal generator

to 1000 microvolt, no modulation.

g. Adjust the frequency of the signal generator to 200 kc (the same as the receiver) as

determined by a zero beat in the headset.

h. Set the BFO-OFF switch on the control

unit to OFF.

i. Adjust the output of the signal generator

to 40 microvolt.

j. Loosen the locknut on R131 (fig. 2-8).

k. Adjust R131 fully clockwise. The needle

of the BEARING INDICATOR on the test set

should fluctuate several degrees on either side

of the actual indication.

Note. Resistor R131 is the adf hunt control. It is used

to adjust the amount of adf needle activity (fluctuation

about the actual bearing indication). When R131 is

fully clockwise, the time required to obtain a bearing is

minimum but the needle activity is maximum. As R131

is turned counterclockwise, the needle activity decreases,

but the time required to obtain a bearing increases and

the resolution (accuracy) of the indication may be

degraded. The amount of needle activity can be set as

desired M long as the resolution (l below) and the

speed required to obtain an indication ( m below) are

within the prescribed limits.

L Check. the resolution as follows:

(1)

(2)

(3)

(4)

Note the indication of the BEARING

INDICATOR on the teat set.

Adjust the LOOP control on the control unit to the L side, and then release

the LOOP control. Note the indication

of the BEARING INDICATOR when

the needle of the BEARING INDICATOR resolves itself to its previous

position.

Adjust the LOOP control to the R

side, and then release the LOOP

control. Note the indication of the

BEARING INDICATOR when resolving is complete.

The indications in (2) and (3) above

should not exceed the indication in ( 1 )

above by more than 2 degree.

m. Check the bearing speed as follows:

(1)

(2)

(9)

Adjust the TUNE control on the control unit for 300 kc.

Set the BFO-OFF switch on the control unit to BFO.

Adjust the frequency of the signal

generator to 300 kc as determined by

a zero beat in the headset. It may be

necessary to increase the output level

of the signal generator while zero

beating.

Change 5 3-29
TM 11-5822-225-35

(4)

(5)

(6)

(7)

(8

(9

(10)

Set the BFO-OFF

trol unit to OFF.

Adjust the output

switch on the conof the signal generator to 40 microvolts.

Set the function switch on the control

trol unit to LOOP.

Note the indication of the BEARING

INDICATOR on the test set.

Adjust the LOOP control on the control unit so that the indication on the

BEARING INDICATOR is 175 degrees to the right or left of the indication in (7) above.

Observe the BEARING INDICATOR,

return the function switch on the control unit to ADF, and measure the

time required for the BEARING INDICATOR to reposition at the indication in (7) above.

The time required in (9) above should

not exceed 7 seconds.

n. If necessary, readjust R131 to meet the

requirements of l and m above. Then tighten

the locknut on R131.

3-21. Inverter Voltage Adjustment

a. Remove two screws which secure the protective plate marked INVERTER on the front

panel of the test set.

b. Disconnect the inverter which is normally

part of the test set.

c. Connect cable W4 of the test set between

P1 on the inverter and the connector marked

INVERTER on the test set.

d. Connect cable W1 of the test set between

J7 on the test set and a 27.5-volt dc power

source.

e. Set the DC POWER switch on the teat set

to ON.

f. Set the RECEIVER-CONTROL switch on

the test set to CONTROL.

g. Connect the ac voltmeter to the test

point located in the center of the 1A fuse

holder cap on the test set.

h. Loosen the locknut on R1 (fig. 2-25) on

the inverter, and adjust R1 for an indication

of 26 ±2.0 volts on the ac voltmeter.

i. Tighten the locknut on Rl.

3-21.1. Inverter Frequency Adjustment

NOTE

Capacitor C6 is selected from 2.2 μF, 3.3

μF, 3.9 μF, 4.7 μF, 6.8 μF, or 10 μF to obtain a frequency of 400 ±40 Hz from the

inverter. This selection is necessary due

to variations in components of the inverter circuitry.

a. Remove two screw’s that secure the protective plate marked INVERTER on the front panel

of the test set.

b. Disconnect the inverter that is normally part

of the test set.

c. Connect cable W4 of the test set between P1

on the inverter and the connector marked

INVERTER on the test set.

d. Connect cable W1 of the test set between J7

on the test set and a +27.5-volt dc power source.

e. Set the test set RECEIVER-CONTROL

switch to CONTROL.

f. Connect the frequency meter to the test point

located in the center of the 1A fuseholder cap on

the test set.

g. Refer to figure 2-2.5. Loosen the locknut on R1

and position R1 fully clockwise.

h. Refer to figure 2-25 and note connections for

capacitor C6. Unsolder and disconnect both leads

of C6.

i. Select a value for C6 (2.2 μF, 3.3 μF, 3.9 μF,

4.7 μF, 6.8 μF, or 10 μF) and connect to terminals

noted in step h.

j. Set the test set DC POWER switch to ON and

note frequency on frequency meter,

Ii, Repeat steps i and j to select a value for C6

that will provide a frequency of 400 ±40 Hz from

the inverter.

1. After the proper capacitor value is determined, set the test set DC POWER switch to OFF.

Replace C6 with the new value.

m. Remove the frequency meter and connect

the ac voltmeter to the same test point.

3-30 Change 5
TM 11-5826-225-35

n. Set the test set DC POWER switch to ON,

and adjust R1 for an indication of 26 ±2.0 volts on

the ac meter.

o. Set the test set DC POWER switch to OFF,

and tighten the locknut on R1.

3-22. Control Unit Alignment

NOTE

Refer to figure 5-17 throughout the alignment of the control unit.

a. Vertical Alignment of Dial Drum.

(1) Set the range switch to 190-400.

(2) Loosen two setscrews (78) and rotate collar

(77) until the band markings around the top of dial

drum (41 ) are clearly visible through the FREQUENCY window on front panel (93). Tighten one of the

setscrews (78).

(3) Rotate the TUNE knob (97) in either direction. If the bottom of the dial drum (41) rubs frame

(136) loosen the one setscrew (78) and readjust collar

(77) until dial drum (41) no longer rubs frame (136).

Tighten two setscrews (78).

(4) Set the range switch to 840-1750,

(5) Rotate the TUNE knob (97) in either direction. The band markings around the bottom of dial

drum (41 ) should be clearly visible through the FREQUENCY window on front panel (93), and the top of

dial drum (41 ) should not rub frame (136). If’ necessary, loosen two setscrews (78) to readjust collar (77).

(6) Set the range switch to 190-400, and repeat

(3) above.

b. Dial Drum Rotational Limits.

(1) Set range switch to 850-1750.

(2) Rotate the tune control clockwise. Loosen

setscrews (44) and rotate gear (43) until alignment

mark on dial drum is aligned with hairline on glass frequency window. Tighten setscrews.

(3) Loosen two setscrews (71), and rotate the

TUNE control to the maximum counterclockwise position.

(4) Apply blue varnish to the threads of two

setscrews (71 ).

(5) Tighten two setscrews (71).

c. Alignment of Tuning Synchro.

(1) Remove the control unit contained in the test

set .

(2) Connect P1 of the test set to P301 of the control unit to be checked. Keep the control unit outside

the test set.

(3) Connect the test set to the equipment as

shown in figure 2-19.

(4) Set the function switch on the control unit to

ADF.

(5) Set the range switch on the control unit to

840-1750.

(6) Rotate the TUNE control until the small circle between 1,400 and 1,500 kc is bisected by the

hairline in the frequency window.

(7) Set the RECEIVER-CONTROL switch on

the test set to CONTROL.

(8) Set the POWER switch on the test set to ON.

(All other switches and controls on the control unit and

the test set may be in any position.)

NOTE

In (9) below, do not allow spur gear (122) or

spur gear (123) to become disengaged with

spur gear (120). Disengagement will cause

loss of spring loading between spur gears

(122, 123). Refer to paragraph 3-6c to

restore spring loading.

(9) Loosen two setscrews (127), and use a narrow- bladed screwdriver to rotate the shaft on transmitter synchro (156) until the BEARING INDICATOR

on the test set indicates exactly 239 degrees,

(10) Apply blue varnish to the threads of two

setscrews (127).

(11) Tighten two setscrews (127).

(12) To check the accuracy of the transmitter

synchro, perform the procedures in (a) and (b) below.

(a) Rotate the TUNE control until 1,700 kc is

indicated in the FREQUENCY window. The BEARING INDICATOR on the test set should indicate 203

± 1.0 degrees.

(b) Rotate the TUNE control until 850 kc is indicated in the FREQUENCY window, The BEARING

INDICATOR on the test set should indicate 343

± 1.0 degrees.

(13) Set the POWER switch on the test set to

OFF.

(14) Disconnect P1 on the test set from P301 on

the control unit.

(15) Install original control unit in the test set.

Change 5 3-31

TM 11-5826-225-35

CHAPTER 4

GENERAL SUPPORT AND DEPOT INSPECTION PROCEDURES

Section 1. GENERAL SUPPORT

4-1. General

a. Test procedures are prepared for use by

Signal field maintenance shops and Signal service organizations responsible for general support maintenance of electronic equipment to

determine the acceptability of repaired electronic equipment. These procedures set forth

specific requirements that repaired electronic

equipment must meet before it is returned to

the using organization. The test procedures

may also be used as guide for the testing

of equipment that has been repaired at direct

support maintenance if the proper tools and

test equipments are available. A summary of

the performance standards is given in paragraph 4-19.

b. Comply with the instructions preceding

the body of each chart before proceeding to

the chart. Perform each test in sequence. DO

not vary the sequence, For each step, perform all the actions required in the Test equipment control settings and Equipment under

test control settings columns; then perform

each specific test procedure and verify it

against its performance standard.

4-2. Test Equipment, Tools, and Materials

Required 

a. Test Equipment.

Nomenclature

Test Set, Direction

Finder Set

AN/ARM-93.

RF Signal Genera.

tor AN/URM-25

( ).

Multimeter

TS-352/U.

Headset, 600-ohms

impedance.

Federal Stock No. Technical Manual

TM 11-6625-821-12

TM 11-5551

TM 11-5527

4-3. Test Facilities

A dc power source of + 27.5 volts capable of

supplying a current of 2 amperes is required

to furnish the operating voltages for the receiver through Test Set, Direction Finder Set

AN/ARM-93. The negative side of the dc

power source shall be grounded. If a battery

eliminator is used, the peak ac ripple voltage

shall not exceed 1.4 volt rms. Unless otherwise specified, all test procedures shall be performed under the following conditions:

a. Test Requirements. With the exception of

physical tests, all performance tests are to be

conducted with the receiver connected to, and ‘

or the inverter and control unit installed in,

Test Set, Direction Finder Set AN/ARM-93 as

shown in the illustrations associated with the

following charts.

b. External RF Interference. Radiated electromagnetic fields in the test area shall not

exceed 10,000 microvolt per meter in the frequency range of 100 kc to 3,000 kc.

4-4. Modification Work Orders

The performance standards listed in the tests

(paras 4-5 through 4-18) are based on the

assumption that applicable modification work

orders have been performed.

Change 3 4-1/(4-2 blank)

4-5.

4-3
Figure 4-1. Control unit test.

4-4
4-6.

Change 4 4-5
4-6 Change 3
Change 4 4-6.1








4-10

Change 1 4-13
4-14 Change 5
Change 5 4-14.1
4-14.2 Change 5
Change 

5 4-14.3
Figure 4-5.

4-14.4 Change 1
4-11.

Change 4

4-15
Figure 4-6. Receiver tuning and switching time test.

4-16
4-12.

4-17
4-1

8 Figure 4-7. Recciever muting test.
4-13.

4-19
4-20
4-14.

Change 3 4-21

/(4-22 blank )

4-15.

4-23
Figure 4-9.

4-24

Change 4
4-16.

Change 5 4-25
TM 11-5826-225-35

Figure 4-10. Loop antenna test.

Change 4 4-26
4-18.

4-27
TM 11-5826-225–35

4-19. Summary of Test Data

4-28 Change 4
TM 11-5826-225-35

Section II. DEPOT INSPECTION STANDARDS

4-20. Applacability of Depot inspection

Standards

a. The tests outlined in this section are designed to measure the performance capability

of a repaired equipment. Equipment that is to

be returned to stock should meet the standards given in these tests.

b. Applicable procedures of the Army depots

performing these tests and the general standards for repaired electronic equipment given

in TB SIG 355-1, TB SIG 35S-2, and TB SIG

355-3 form a part of the requirements for testing this equipment.

4-21. Test Procedures

a. The teat equipment and power required

for depot inspection standards are the same as

indicated in paragraph 4-2.

b. The operational teat for depot inspection

standards are the same as the tests given in

paragraphs 4-8 through 4-18. Perform the

tests in the order in which they are given, and

observe that the results meet the minimum

standard indicated in each test,

4-6

4-7

4-8

4-9

4-10

4-11

4-12

4-13

4-14

4-15

4-16

4-17

4-18

Change 5 4-29
TM 11-5826-225-35

—

Figure 4-11. Color code markings for MIL-STD

resistors.

4-30
TM 11-5826-225-35

CHAPTER 5

ILLUSTRATIONS

This chapter contains illustrations which have been initially referenced in chapters 1,

2, and 3.

NOTE

Revision history for the various units is shown in the notes

column on the applicable schematic diagrams. Effectivities are

identified by the following methods: MCN (manufacturer control number), starts with 3-digit number (101) and up; CI (configuration identifier), a 5-digit number; or REV LTR (revision

letter), where a dash (–) denotes the original, the letter A

represents the first change, the letter B represents the second

change, etc. One of the above methods may be used to denote

revision effectivities.

Change 5 5-1




Figure 5-4.

Change 1 5-7



TM 11-5826-225-35

Figure 5-7. Mixer and local oscillator, schematic diagram.

Change 1 5-12.1






















TM 11-5826-225-35

INDEX

Alignment:

Control unit

General - __________________

Inverter, frequency adjustment ..__ ---- --------------

Inverter voltage adjustment --------------------- ----

Receiver:

Adf hunt control, adjust

ment ---- ------------

Audio and IF gain adjustment

First RF amplifier . . . .

Function and range

switch, centering adjustmen t .

General

Local oscillator ___

Resolver servo system

RF . . . . . . . . .

RF balance, adjustment . .

Servo balance, adjustment .- . . . . .

Slow slew speed

adjustment -----

Test equipment and additional equipment

Tuning Capacitor, adjustment and synchronization

Tuning servo tachometer

feedback, adjustment

110-Hz oscillator

frequency

adjustment . . . . . . . . . .

90-degree phase

shift adjustment

Antenna, loop :

Functioning, detailed

General support testing:

Physical tests and inspection --

Test -- .

Troubleshooting:

Test setup . . . . . . . .

Antenna AS-1863/ARN-83.

(See antenna, loop)

Control unit:

Alignment

Functioning, detailed

General support testing:

Physical teats and inspection

Paragraph

3-22

3-8

3-21.1

3-21

3-20

3-17

3-16

3-11

3–8

3-13

3-18

3-14

3-15

3-19

3-19.1

3-9

3-12

3–10

3-17.1

3-17.2

1-24

4-17

4-18

2-16

3–22

1-25

4-5

Page

3-28

3-19

3-28

3-27

3-26

3-25

3-24

3-20

3-19

3-21

3-25

3-22

3-23

3-26

3-26.1

3-19

3-21

3-19

3-26

3-26

1-26

4-27

4-29

2-43

3-28

1-25

4-3

Test ___________________

Repairs:

Disassembly _____________

Reassembly and lubrication -. .- ----------

Troubleshooting:

Localizing troubles __

Test procedure ----- --

Test setup

Direction Finder Control C-6899/

ARN-83. (See control unit. )

Functioning, general :

Block diagram, general

system _- --

Block diagram, overall

functional ------

Functioning, interunit circuit:

Function and frequency

selection

General

Manual audio and RF

gain control -.

Manual loop control

Receiver bfo switching

Receiver tuning

Receiver tuning meter

General parts replacement

techniques .

Periodic lubrication

Removal and replacement

techniques

Troubleshooting,

General

Organization of procedures

Test equipment required

Functioning, detailed.

Antenna

Control unit

General, additional equipmen t

Inverter

Receiver:

Audio amplifiers

Automatic gain control

and receiver muting

Balanced modulator

Bfo, detector, and

limiter

General

Paragraph

4-6

3-5

3-6

2-12

2-11

2-10

1-2

1-3

1-27

1-26

1-30

1 -29

1-31

1-28

1-32

3-1

3-7

3-2

2-1

2-2

2-3

1-24

1-25

1-22

1-23

1-15

1-16

1-7

1-14

1-4

Page

4-5

3-11

3–13

2-39

2-35

2–35

1-1

1-1

1-25

1-25

1-27

1-27

1-29

1–26

1-30

3-1

3-19

3-1

2-1

2-1

2-2

1-25

1-25

1-22

1-22

1-14

1-15

1-7

1-13

1-5

Change 5 I-1
TM 11-5826-225-35

Paragraph

IF amplifier ------------

Local oscillator

Mixer ---- ---- ___

Mixer input turned

circuits . .. -._. _

110-cps oscillator and

amplifier ------ ----

110-cps variable phase

signal and synchronous filter . ---

Phase shift network and

second RF amplifier _

Push-pull RF amplifier ._

Receiver loop antenna and

5 - 1

5 - 1

goniometer circuit functioning ----------- _

Resolver servo amplifiers _

Sense antenna input network ______ ___________

Tuning servo amplifiers __

Voltage regulator . .._ -_

Functioning, Direction Finder

Set AN/ARN-83:

Block diagram:

General system _________

Overall functional ______

Scope ------------- -----

Functioning, interunit circuit:

Function and frequency

selection ____________

General .

Manual audio and RF gain

control ------------------

Manual loop control _._.-. -_

Receiver bfo switching _

Receiver tuning _______ ..__

Receiver tuning meter ___ __

General support testing procedures.

Antenna AS-1863/ARN-83

physical tests and inspec.i.

tion ..- ----- -------

Control unit test ______ _.. _

Direction Finder Control

C–6899/ARN-83 physical

tests and inspection -----

General _ _________________

Inverter Power, static CV–

2128/ARN-83 physical tests

and inspection ---- . . .

Inverter test

3-26.1

Loop antenna test _

Modification work orders __..

Radio Receiver R-1391/ARN83 physical test and inspection ----------------

Receiver bandwidth test _. ___

Receiver bearing indicator

test -.. . . . . . . . . . . . . . . . . . .

Receiver frequency accuracy

test .

3-26

Receiver muting test --------

l-13

1-11

1-12

1-10

1-19

1-17

1-6

1-9

1–5

1-18

1-8

1-20

1-21

1-2

1-3

1-1

1-27

1-26

1-30

1-29

1-31

1-28

1-32

4-17

4-6

4-5

4-1

4–15

4-16

4-18

4-4

4-7

4-9

4-11

4-8

4-13

Page

1-12

1-11

1-12

1-9

1-18

1-15

1-7

1-9

1-5

1-17

1-9

1-19

1-20

1-1

1-1

1-1

1-25

1-25

1-27

1-27

1-29

1-26

1-30

4-27

4-5

4-3

4-1

4-25

4-27

4-29

4-1

4-7

4-11

4-17

4-9

4-21

Receiver sensitivity test ..-__

Receiver tuning and switching

time test . . . . . . . . . . . . . . . .._

Receiver tuning meter test ___

Summary of test data -------

Test equipment, tools, and

materials required ________

Test facilities . . . . . . . . . . . . . .

Illustrations:

General ----------- ---------

List of foldouts - _________

Inverter:

Alignment ______ ____________

Functioning, detailed ________

General support testing:

Physical tests and inspection - . . .. _____________

Test ------ ------------

Troubleshooting:

Isolating trouble within

a stage - -------------

Localizing troubles ------

Test setup ______________

Loop antenna (See antenna loop)

Modification work orders . . . . ..-.

Periodic lubrication ____________

Radio Receiver R-1391/ARN-83.

(See receiver.)

Receiver:

Alignment:

Adf hunt control, adjustment -------------

Audio and IF gain adjustment -------------

First RF amplifier ______

Function and range

switch, centering adjustment ____________

General ----------------

Local oscillator _________

Resolver servo system, ---

RF ------------ --------

RF balance, adjustment _

Servo balance, adjustment -----------------

Slow slew Speed

adjustment --------------

Test equipment and additional equipment ------

Tuning capacitor, ajustment and synchronization __________________

Tuning servo tachometer

feedback, adjustment _.

110-Hz oscillator

frequency

adjustment --------------

90-degree phase

shift adjustment ---------

4-10

4-12

4-14

4-19

4-2

4-3

5-1

5-2

3-21

1-23

4-15

4-16

2-15

2-14

2-13

4-4

3-7

3-20

3-17

3-16

3-11

3-8

3-13

3-18

3-14

3-15

3-19

3-19.1

3-9

3-12

3-10

3-17.1

3-17.2

Page

4-13

4-19

4-23

4-30

4-1 

4-1

3-27

1-22

4-25

4-27

2-41

2-40

2-40

4-1

3-19

3-26

3-25

3-24

3-20

3-19

3-21

3-25

3-22

3-23

3-26

3-19

3-21

3-19

3-26

I-2 Change 5
TM 11-5826-225-35

Functioning, detailed:

Audio amplifiers

Automatic gain control

and receiver muting

Balanced modulator

Bfo, detector, and limiter

General ___. _. .-. _ .

IF amplifiers

Local oscillator

Mixer -----------

Mixer input tuned circuits .

110-cps oscillator and

amplifier __ ._.. . . ---

110-CPS variable phase

signal and synchronous filter ------------

Phase shift network and

second RF amplifier .

Push-pull RF amplifier

Receiver loop antenna and

goniometer circuit functioning . . -- -----------

Resolver servo amplifiers _

Sense antenna input network _________________

Tuning servo amplifiers

Voltage regulator _______

General support testing:

Bandwidth test ______ -_

Bearing indicator test --

Frequency accuracy test

Muting test ------ ._

Physical tests and inspection ----------- ._

Sensitivity test --- __ __

Tuning and’ switching

time test -------------

Tuning meter test __. _..

Repairs:

Disassembly .- ----- __

Reassembly and lubrication . . . . .._- . . . . .

Troubleshooting:

Additional data _

Isolating trouble within

a stage --------- ___

Paragraph

1-15

1–16

1-7

1-14

1-4

1-13

1-11

1-12

1-10

1-19

1-17

1-6

1-9

1–5

1-18

1-8

1-20

1-21

4-9

4-11

4-8

4-13

4-7

4-10

4-12

4-14

3-3

3-4

2-9

2-8

Page

1-14

1–15

1-7

1-13

1–5

1-12

1-11

1–12

1-9

1-18

1–15

1-7

1-9

1-5

1-17

1-9

1-19

1-20

4-11

4-17

4–9

4–21

4-7

4-13

4-l9

4-23

3–1

3-4

2-32

2-29

Localizing troubles

Signal substitution

Stage-gain measurements

Teste setup

Repairs:

Control unit:

Disassembly

Reassembly and lubrication

Removal and replacement

techniques 

Scope ------------------ ____ ---

Summary of test data __

Test data, summary -------------

Test equipment:

Alignment __________________

General support testing ---

Troubleshooting _____ ._ ..__

Test facilities -------- -- __ ______

Troubleshooting:

Antenna:

Test setup _ _____________

Control unit:

Localizing troubles _____

Test procedure __________

Test setup ______________

General techniques:

Organization of procedures ----------- ----

Test equipment required -

Inverter:

Isolating trouble within

a stage --------------

Localizing troubles -----

Test setup ---------------

Receiver:

Additional data ________

Isolating trouble within

a stage ------- ______

Localizing troubles _.. ____

Signal substitution ______

Stage-gain measurements --- -----

Test setup _. ._. ______

Paragraph

2-5

2–6

2-7

2-4

3-5

3-4

3–2

1-1

4-19

4-19

3-9

4-2

2-3

4-3

2-16

2-12

2-11

2-10

2-1

2-2

2-3

2–15

2-14

2-13

2-9

2-8

2–5

2-6

2–7

2-4

Page

2-4

2-22

2-25

2-3

3-11

3-4

3-1

1-1

4-30

4-30

3-19

4–1

2-2

4-1

2-43

2-39

2-35

2-35

2-1

2-1

2-2

2-41

2-40

2-40

2–32

2-29

2-4

2-22

2-25

2-3

I-3

TM 11-5826-225-35

By Order of the Secretary of the Army:

Official:

J. C. LAMBERT,

Major General, United States Army,

The Adjutant General.

HAROLD K. JOHNSON,

General, United States Army,

Chief of Staff.

Distribution:

To be distributed in accordance with DA Form 12–36 requirements for Direct and General

Support (Unclas) Maintenance Literature for the OV-lA, OV-lB, OV-lC, U–8F, CH-47A, UH1B and UH–lD Aircraft.

* U.S. GOVERNMENT PRINTING OFFICE : 1992 0 - 311-831 (43955)


PIN :028228-000