From: jep@unl.edu (joseph panarelli)
Newsgroups: rec.radio.shortwave
Subject: ICF SW77 Mute Mod
Date: 25 Jan 1993 16:43:24 GMT
Organization: University of Nebraska--Lincoln	
Distribution: world
NNTP-Posting-Host: unlinfo.unl.edu
Summary: Remove muting from tuning
Keywords: ICF SW77, ShortWave, Modifications, Muting

The following are instructions on how to disable the muting circuit on
a Sony ICF-SW77.  Performing this procedure will no doubt violate your 
warranty (if the service center can tell you did it.)  I have used my radio with the 
modification for only a few hours so I can not guarantee that there will be no long
term damage to your radio from this procedure.  Proceed at your own risk.

The radio will no longer mute while changing stations, scanning or 
while powering on/off.  You may find the resulting noise more annoying than 
the muting.

Please read these instructions before starting.

You will need a #1 Phillips, Scotch brand Magic Transparent Tape and a
sharp knife of scissors, tweezers (optional).

Make sure you are not carrying any stray static fields.  Touch 
something that is grounded or better yet use a grounding pad and wrist strap.  (I have 
not used one and have had no trouble with the 77.)  Slide the power switch to 
the lock position.  Remove the batteries (you will not loose your station 
presets, but will loose timer, time and Q!, Q2 settings after ~10 min.)  Flip the 
top button panel cover up.  Remove the six screws and gently remove the back 
cover by pulling it upward, while  noting how the top button panel slides into 
the front cover.  The 77 is built into a sub chassis which you will not need to 
remove from the front cover.  If the chassis gets separated from the front, 
you may need to remove it completely to reposition the keyboard keys.  Make 
sure the power switch is in the lock position before reassembly or else the 
lock switch may be damaged!

On the RF board, locate CN 401, a 15 Conductor connector.  This may be
found approximately 10cm from the left edge of the circuit board, just above
the battery compartment.  The flexible PCB ribbon connected to CN 401 
brings signals from the microprocessor board.  The mute signal is carried in 
conductor 9, that is, the ninth conductor from the RIGHT edge of the ribbon.

The ribbon is held into the connector by a wedge on the top side of 
the ribbon. This wedge must be pulled out towards the battery compartment to 
release the ribbon.  There are tabs on the right and left edges of the wedge which
may be used with fingernails for removal.  Note which sides of the wedge are
top/bottom.

Once the ribbon is released, you need to cut a small sliver of Scotch 
tape with which to insulate conductor #9.  Use tweezers or the tip of the knife 
to position the sliver of tape.

Reassemble, paying attention to how the top button panel slides into 
the front case portion.  When reinstalling the six screws, start by turning CCW 
to find the proper threads, thus avoiding cutting new threads and weakening 
your case.
                 Enjoy! (?)

Notes:
The signals on CN 401 are as follows::
1:  6V BACKUP
2:  6V TR
3:  CLK
4:  DAT
5:  LAT1
6:  LAT2
7:  BCS
8:  POWER
9:  MUTE
10: SD1
11: 
12: BATTDET
13: BEEP
14: SMETER
15: GND
It may be possible to adjust the S Meter through the signal on 
conductor 14.  I will post if I can figure something out.

If your radio does not have full coverage (76-108MHz FM 150-29999.99 
KHz) it is possible to restore coverage by de-soldering the three solder
pads on the front of the microprocessor board.  these pads are located
1.5cm from the top edge and 4.5cm from the right edge.

Has anyone noticed this bug?  when the radio turns on in the SSB mode,
the frequency is ~100 Hz off from what is displayed.  This error is not 
corrected until the SSB mode is exited and re-entered.  This problem was found 
on the sample unit at EEB as well.

Stephen Panarelli             University of Nebrasks-Lincoln
jep@unlinfo.unl.edu           'I own no stock in 3M'
Comments: Gated by NETNEWS@AUVM.AMERICAN.EDU