Restoration of a really old hp5065a - Page 1
Forum section: electronics / general

author: syau
author_rank: Frequent Contributor
timestamp: November 26, 2019, 05:11:13 am
content: For reason that I am not able to explain, I decide to try my luck to score this unit:https://www.eevblog.com/forum/metrology/really-old-hp5065a-on-ebay-right-now!/Now it start its restoration journey.Battery has been removed by the previous ownerResistance measurement on the SMB connector in front of the RVFR = 3.33k ohm.Just ordered some 100uF and 20uF capacitor from RS, will replace it before power up.Note: Have difficult to pull out come of the cards, will attempt again when I got the replacement capacitor

author: edpalmer42
author_rank: Super Contributor
timestamp: November 26, 2019, 05:54:52 am
content: Congratulations on your purchase.If you haven't already found them, there are a couple of threads on the 5065A:https://www.eevblog.com/forum/metrology/hp-5065a-rubidium-standard-repair-log/msg2271831/#msg2271831https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/msg2440983/#msg2440983There's also a few web sites with good info on repairs, modifications, and general info:http://phk.freebsd.dk/hacks/HP5065A/index.htmlhttp://www.timeok.it/hp5065a-corner-3/There are others, but that's enough for now!Good luck!

author: syau
author_rank: Frequent Contributor
timestamp: November 26, 2019, 06:57:51 am
content: Found R34 crack on the A11, the colour band show ORANGE GREEN GOLD GOLD which is 3.5 ohm but the manual show 1.5 ohm

author: dietert1
author_rank: Super Contributor
timestamp: November 26, 2019, 09:57:07 am
content: Maybe orange is brown. Can't you check the other one to find out? Note: Those old carbon resistors may be off much more than 5 %.Regards, Dieter

author: testpoint1
author_rank: Frequent Contributor
timestamp: November 26, 2019, 02:17:13 pm
content: Quote from: syau on November 26, 2019, 06:57:51 amthere is no 3.5OHM resistor for normal, if that is 0.1%, maybe is different.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: November 26, 2019, 04:50:39 pm
content: Syau,The 2 resistors on the A11 are 1.5 Ohm wire wound resistors.Before you do too much repair you need to unplug the A12 RVFR 9 pin jack and measure the following.Measure the impedance between pins 4 and 5 and pins 3 and 4.You should have 50 Ohms on each.Then measure from those 4 pins to the threaded stud sticking out the end of A12.You should not have any continuity!If you do the lamp oven winding has shorted out.Pretty much a show stopper but can with LOTS of effort and patience might be repaired.Also what is the units serial number and what series number is your A7 module.Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: November 27, 2019, 01:56:25 am
content: Hi Corby,The unit serial number is 808-00051 as wrriten on the front panel cover. Unable to locate other data plate on the unitA7 part number: 05065-6010A7 serial number: 916There is also a stamp "1143" on the assy, not sure if it is the manufacturing dateAttached see a photo with better resolutionCheers,Stanley

author: edpalmer42
author_rank: Super Contributor
timestamp: November 27, 2019, 03:03:48 am
content: It might be helpul to pull the 00105 OCXO and test it seperately. Power it up and let it run so that it can settle down and provide good aging numbers while you work on the other preliminary tasks. Knowing that it's working properly will help remove one variable. It might be awkward to try to chase system troubles while the oscillator is aging rapidly.

author: syau
author_rank: Frequent Contributor
timestamp: November 27, 2019, 05:16:30 am
content: Resistance between pin 3 & 4 is 48.56 Ohm but short circuit between 4 & 5May be this the reason why R34 on A11 get fired.Open circuit from those 4 pins to the threaded stud sticking out the end of A12.Looks like I either need to try out Corby’s instructionhttps://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details] https://www.eevblog.com/forum/metrology/hp-5065a-lamp-oven-repair-details!/ unless someone willing to sell me a RVFR

author: edpalmer42
author_rank: Super Contributor
timestamp: November 28, 2019, 05:11:03 am
content: Quote from: syau on November 27, 2019, 05:16:30 amDon't hold your breath on that. I remember a number of months ago someone on ebay paid something like $1K for a RVFR. I don't know what surprised me more - the fact that someone was selling a RVFR by itself or that someone paid that much for it!

author: syau
author_rank: Frequent Contributor
timestamp: November 28, 2019, 06:01:26 am
content: The P2332ADVFEP.009BL quoted by Corby out of stockPlaced a 100ft order of P2332ADVFEP.005WT, same resistance per feet but with thinner insulation.

author: james_s
author_rank: Super Contributor
timestamp: November 28, 2019, 06:55:38 am
content: Looking at that other thread, it doesn't look like too bad of a project. As long as the thing can be disassembled without completely destroying it I don't think it will be hard to repair.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 02, 2019, 06:03:23 am
content: Stanley,If you have not already done so remove the lamp assy. and see if it looks like it got too hot.Also once you get the oven cylinder free you might be able to wind the new heater without machining the slots shown in my post.Let me know once it's out and I can take you through checking if that's feasible.Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: December 02, 2019, 03:13:35 pm
content: Corby,Found 1 screw missing (actually sheared) when I opened the cover, looks like someone has been there beforeClose examination of the light assembly found some greenish in the legs of several resistor (especially the 1k33) and some capacitorLooks like the assembly has also subjected to overheatBRGds,Stanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 03, 2019, 01:07:49 am
content: Stanley,It does not look too bad as far as overheat.The 1.33K will need to be changed as it frequently fails. I use a 1.3K metal oxide resistor.Take the 3 slotted screws out of the lamp assy. to allow the front diffuser to come off.This will expose the lamp. Take a closeup PIX of the spherical lamp with the small coil around it so I can evaluate it.Also remove the 3 screws on the diffuser and remove the perforated lid.I usually have to put it at an angle in a vise and apply pressure sideways to get it to pop free.Then you should see a glass disc convection shield and also the surface of the mirrored portion.If the mirrored portion is corroded and dull you will need to pop off the glass disc (you can push through with your little finger or use a wood dowel to force the disc out of the slot) and then use Aluminum polish to restore the mirror surface.Take a PIX of the now exposed circuit board also.The rest of the unit can be powered up without the optical unit and you can check out the Quartz oscillator and power supplies.Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: December 03, 2019, 02:59:41 pm
content: Corby,Removed the diffuser & reflector as per your instruction, found it is more like a glass cup instead of a disc (it actually come loose when I removed the diffuser (no glue)BRGds,Stanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 04, 2019, 04:16:29 am
content: Stanley,The lamp assy looks pretty good although the reflector does need to be re-polished!Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: December 09, 2019, 08:22:20 am
content: My x’mas project

author: syau
author_rank: Frequent Contributor
timestamp: December 14, 2019, 10:18:11 am
content: Corby,Finally has sometime to continue the project, lamp heater removed, all the remaining resistance still within limit (remaining heater & thermistor x 2).As I don’t have accessed to a turning machine therefore I am thinking of reusing the thermistor and wind the new heater on top of the aluminium housing with a thin layer of ptfe tape.BRGdsStanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 18, 2019, 01:37:11 am
content: Stanley,Yes that is a good option. Rub off as much loose materiel as you can from the inner surface of the "exclusion zone" to give you a little extra room. It's usually powdery and you can at least go down the thickness of the original winding that you can see in the foam. Just don't go crazy as if you go too deep you could damage the remaining wires. Make sure the thermistor is covered in heat sink goop!Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: December 18, 2019, 10:11:18 am
content: Corby,I also managed to drill out the broken screw from the heater housing, do you have any idea on the thread size / pitch? If not, I will “re-condition” the thread using a M2 tap.Note: close examination on the thermistor found the sleeve still in good condition.BRGds,Stanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 18, 2019, 09:35:17 pm
content: Stanley,I believe that the threads are 2/56 on the 3 lamp mounting holes.Cheers,Corby

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: December 31, 2019, 05:33:29 am
content: Stanley,Could you post a PIX of your A15 power supply board?Also before you power it up change the 2 non hermetic electrolytic caps on the A11 board, they almost always are bad.Also open the A7 and A3 modules and check the single 100uf caps inside for signs of corrosion.The A3 is a pain to open.you can shine a flashlight in thru the holes for the matching network and see the + lead of the cap. That's what I usually do instead of opening it up!When you have the time could you maybe trace out the circuitry for the "adj mag field" position of the mode switch? Yours is the only unit I have seen with this switch position and I wonder what it's doing???Good luck on the repair.Corby

author: syau
author_rank: Frequent Contributor
timestamp: January 01, 2020, 12:12:28 pm
content: Photo of the A15 board before repair.Replaced 3 capacitor and 4 diode (with the schottky diode to lower the voltage drop).

author: syau
author_rank: Frequent Contributor
timestamp: January 01, 2020, 12:15:10 pm
content: Repaired the A11 board by replacing two 1.5ohm resistor (1 burnt out) and 2 capacitor

author: syau
author_rank: Frequent Contributor
timestamp: January 28, 2020, 04:38:21 pm
content: Continuous capacitor replacement todayFound that there is evidence of leakage at the bottom of the big C2 capacitorTrying to find a 2800uF 40V replacement which is slim enough to hide in the bottom panel

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: January 28, 2020, 07:14:22 pm
content: Stanley,I've only had to replace those big chassis mounted caps once.I found a replacement that had screw terminals and used a piece of circuit board to make a mount that fit under the original hole.Worked great.Don't forget to check the 100uf cap in the A3 and A7 assemblies.Cheers,Corby

author: james_s
author_rank: Super Contributor
timestamp: January 29, 2020, 01:13:20 am
content: Another thing you can do when replacing big caps like that if you want to preserve the original appearance is to gut the original capacitor and slip a replacement up inside it. That can be tedious to do without damaging the housing but it is possible. It's easier if you can chuck it up in a lathe and neatly cut the bottom plate and then use an endmill to hog out the foil and paper.

author: syau
author_rank: Frequent Contributor
timestamp: January 29, 2020, 07:49:45 am
content: Corby,Opened up the A7 and replaced the 100uF capacitor. During the process, found one capacitor C12 0.0252uF (the one with a thick plastic sleeve) has some “white powder” on it. Cleaned with IPA and looks good.Not sure if it is electrically okAfter 100uF replacementBefore cleaningAfter cleaningBRGds/Stanley

author: syau
author_rank: Frequent Contributor
timestamp: January 29, 2020, 07:58:55 am
content: Corby,For the A3, I shine a light through the opening and the positive terminal of the capacitor looks good so I didn’t bother to open it up.Just measured the main C2 capacitor, only a few hundred pF (not uF), C3 is still around 32xx uF.For the 1.3k resistor in the lamp assembly, is 2W 1% resistor sufficient ?BRGds/Stanley

author: syau
author_rank: Frequent Contributor
timestamp: February 26, 2020, 10:20:50 am
content: Wired a bridge rectifier and an external 3300uf capacitor to the unit, powered up with external 28VDC power supply, no magic smoke(RVFR still not connected)Hooked up to the AC, checked the output of 5MHz, 1Mhz, 100kHz on the check meter, all spot on. The only issue I have is I got a full scale deflection on the meter if I select OSC Oven. I measured the resistance between M & +24V gives 101 ohm which should be normal. Haven’t measured the AC heaterI now connected the 5MHz output to my 53310A to measure the drift.

author: syau
author_rank: Frequent Contributor
timestamp: February 26, 2020, 10:47:26 am
content: Closer inspection found the previous owner has disconnected the 110V AC to the heaterThe resistance if that heater found to be open circuit.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: February 26, 2020, 04:40:11 pm
content: Stanly,The Oscillator will work fine without the AC fast warmup heater. It will just take longer to warmup!Once its warm and you can verify it can be adjusted to exactly 5Mhz the osc oven indication might have come down.If not you can reselect the resistor on A17 to pit it on scale.2W 1% is OK.One other thing, Before you power the receiver up check the the two chassis mounted transistors that go to A11. Make sure they are not shorted.Also once you let the cell and lamp ovens warm up and the meter readings drop down you should test the transistors leakage. I just clip a resistor (500 Ohms or so) across the thermistor pins on A11 and make sure that each oven will completely shut off (meter drops to zero).

author: syau
author_rank: Frequent Contributor
timestamp: February 27, 2020, 12:36:28 am
content: Quote from: 5065AGuru on February 26, 2020, 04:40:11 pmCorby,For the lamp assembly, the 1.33k resistor is open circuit and I replaced with a 1.3k 1% one. I also replaced the 10 ohm on the stand off although the measurement is fine.The 5MHz osc response to the EFC from the front panel and I mange to make it as close as possible to 5MHz

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: February 27, 2020, 02:22:47 am
content: Stanley.You can apply +20Vdc to the lamp assy when it out of the unit and make sure it starts. Should draw about 140mA and after the lamp starts it drops down a bit.The lamp should light within a minute or so cold and it will look pale whitish/purple.If you pull a hot lamp assy out of the oven with power applied it should be deeper purple.Sounds like the Quartz oscillator is OK!Good luck

author: syau
author_rank: Frequent Contributor
timestamp: February 27, 2020, 03:16:46 am
content: Corby,RVSP post repair photo:For the lamp heater, I am using 11’ of wire, end up to around 52ohm, LOCTITE SI 5145 is used to secure the lamp heater into the RVSP which I purchased from RS.

author: syau
author_rank: Frequent Contributor
timestamp: February 27, 2020, 03:30:37 am
content: Quote from: 5065AGuru on February 27, 2020, 02:22:47 amThe lamp drawn around 150mA (reading from the uncalibrated power supply) after start, 160mA when cold.

author: syau
author_rank: Frequent Contributor
timestamp: February 29, 2020, 01:32:15 pm
content: Corby,Found A11 Q4 open circuit, lucky same transistor being used on the battery charge A2.Temporary fitted the RVFR and power up the unit. Cell oven drop to 30 and lamp over drop to 38 after an hour or so. Photo I show around 23 but 2nd harmonic has no reading.Should I leave it on for a while or follow your procedure to connect a 5vdc and a 5 ohm 10W resistor to the TED and try to de-flood the cell ?BRGds/Stanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 01, 2020, 12:40:43 am
content: Stanley,You need to scope TP2 on A7 and then in open loop tune thru C.F. using the fine quartz.If you don't see a signal as you move plus minus .3 HZ then the cell might be flooded.Unfortunately I don't think your unit has a TED! The very early units did not have it.If you have a black/red twisted pair coming out of the receiver cylinder at the rear along with the cable going to the A7 input you have a TED. If not we will have to proceed differently!Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: March 01, 2020, 05:21:46 am
content: I am not able to get a signal on A7 TP2 when I move the freq +/- .3Hz so likely flooding occurred. I did some testing on the A7 by disconnecting the J1 and touch the center conductor and the circuit works.My RVFR did fitted with TED. I will try to use a sourcemeter to apply 1A.

author: dietert1
author_rank: Super Contributor
timestamp: March 01, 2020, 11:20:40 am
content: As i never had this problem with our FE 5680A rubidium oscillators, can anybody write a sentence or two what is meant by "cell flooding"? The HP 5065a service manual used this term without explanation.Regards, Dieter

author: syau
author_rank: Frequent Contributor
timestamp: March 01, 2020, 12:22:22 pm
content: Quote from: syau on March 01, 2020, 05:21:46 am

author: bsdphk
author_rank: Regular Contributor
timestamp: March 01, 2020, 02:19:34 pm
content: The cell in the the 5065 is very different from those in small telecoms Rbs, in particular it has "too much" Rb in it.This surplus Rb is supposed to freeze in a small "arm" on the side of the bulb, and a thermo-electric cooler ("TEC") lowers the temperature a tad to make that happen.I belive the original idea was to make sure there were enough Rb to provide vapour saturation also after many years where some of the Rb was absorbed into the glass.

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 02, 2020, 12:58:20 am
content: Stanley,I usually apply 5VDC through a 5 Ohm 10Watt resistor to provide the 1Amp TED current.Leave the entire unit powered up with the 1Amp applied for a 5 or six days.If you still can't see a signal other stuff needs checking, this can all be done while the 1Amp is applied to the TED.-Turn the two top pots on A3 max CW-what's the TP2 DCV reading on A3-what's the synthesizer frequency reading-What is the amplitude of the 137Hz out of A8. (across the chassis mounted mica cap)- Watch A7 TP2 with a .25Hz offset on the 5Mhz output and adjust the A3R40 (pot on the side of A3) through its range and see if a signal appears.Cell flooding is where too much Rubidium enters the resonancecell and blocks the light.Usually after a unit has been in extended storage or storage at elevated temperature.This is mainly a 5065A problem although older Varian V4700 and R20 unitsalso can be effected.The procedure in the manual cools the tip of the stem and collects theRubidium back where it belongs!This takes about a week and then after reconfiguring the TED back tonormal cooling levels another week to stabilize the Rubidium level in thecell. Modern telecom units utilize starved cells and don't have this problem.Normal TED operation regulates the proper level of Rubidium in the cell.Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: March 16, 2020, 04:20:18 am
content: Hi Corby,Made some measurement on A3P2 - 5MHz, 7.76Vp-pP1 - 136.6Hz 180mVp-pTP2 - 393mVJ8 - 60MHz 20mVp-pLooks like the AGC not working, I removed Q4 and it measured fine, so as C12.BRGDs/Stanley

author: syau
author_rank: Frequent Contributor
timestamp: March 16, 2020, 10:01:02 am
content: Hi Corby,After battle for an hour, found Q2 D-S open circuit, I relocate Q5 over and then substitute Q5 with a J304 FET (I only have this on hand).J8 output jump back to 5.52Vp-pWill take some break and continue tomorrow.BTW, any replacement suggestion for 1855-0327 (2N4416 ?)BRGds/Stanley

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: March 16, 2020, 11:48:20 pm
content: Stanley,While watching A3 TP2 adjust the A3R40 (pot on the side of A3) max CCW and then turn CW and see if you can get a voltage of 4 to 5 VDC. (the first peak if you see peaks)Then look at A7 tp2 in open loop while tuning fine Quartz plus minus .25HZ (at 5Mhz) and see if you get a 137Hz signal at the extremes and 274Hz when on frequency.I've only used the 2N4416, not sure what an ideal replacement is.The main thing is to find the signal, if it can be seen at all then the other parameters can be aligned to maximize the signal.If still no signal we will have to try some more tests.Do you have an HP8660 or HP3325A?Cheers,Corby

author: syau
author_rank: Frequent Contributor
timestamp: April 03, 2020, 12:11:16 am
content: I ordered some 2N4416 from Mouser (leaded version, not cheap) but forgot to change the shipping address to my home. Due to work from home policy, I can only back to the office next week to collect it.Yes, I got a 3325B, will dig it out from storage and test it.

author: syau
author_rank: Frequent Contributor
timestamp: July 29, 2020, 12:47:55 am
content: Quote from: syau on April 03, 2020, 12:11:16 amReplacing the 1855-0081 with 2N4416 improved the situation but not fixing it. Digging through the service manual found the equivalent is 2N5245. Found some NOS from evilbay and after replacing all the 1855-0051 with 2N5245 all level back to specification including the TP2 voltage (4.7V).When I fitted back the A3 to the unit, I accidentally crushed 1 SMB jack

author: 5065AGuru
author_rank: Frequent Contributor
timestamp: July 29, 2020, 03:04:10 am
content: Stanley,Hi! I can send a couple SMB if you would like?Have your run the TED for a week?When the lamp oven is warmed up did you happen to observe the lamp color by pulling the lamp assy out while still hot? I'm concerned about the color of your cold lamp in the picture.Did you measure the lamp ovens temperature after the repair? (Did you use the original thermistor?)If your 60Mhz looks OK now can you see a signal yet when you adjust the Quartz fine frequency across resonance at A7TP2?What is the frequency and amplitude of the synthesizer output?If you measure with an ohmmeter set to test semiconductor junctions both ways the 60Mhz input jack to the optical unit do you show a junction in one of the directions?If still no A7 TP2 signal we have to try testing the optical unit via an external signal.Did you dig up the HP 3325B?What synthesizer thumbwheel setting as shown on the optical unit label?I'll need to try this on the unit I have on the bench and once I get the details straight I'll post instructions.Cheers,Corby