No.064 - Agilent E3632A Power Supply Repair - Part 1

[@TheDefpom]

The architecture of that unit is basically the same as the units I fixed. Check the power supplies of the gpib section, I found a bad supply there can kill it, also check the front panel uP isn’t getting hot, I had to replace that myself too and it was giving a similar symptom.

[@IanScottJohnston]

All power supplies (there are quite a few) are fine on both the earth referenced and floating sections of the main board, nothing overly hot. I am working on a Part 2 video today actually, the Cpu clock, reset circuit, addess/data bus all look active and with no shorts (can usually see this on a scope). Plenty more to test though, this is looking like a proper fault....great fun!

[@DextersTechLab]

Wow, this one looks a right PITA to fix up, looking forward to seeing part 2!

[@knunne1]

I love to follow you logic in troubleshooting the problem, thanks for the video! Look forward to the next installment.

[@GadgetUK164]

Looking forward to part 2 =D

[@PapasDino]

Great, a challenging repair! The game is afoot!

[@jasonbrindamour903]

Holy cow! That transformer is ginormous!

[@Ynformatics]

My experience is with an E3631A but they are a similar architecture. Be careful probing the display section. It's easy (well it was for me) to send 17V where it's not wanted! Maybe the previous repair attempt has done this. I had to remove the VFD and replace some blown comparators and the custom ASIC (fortunately available from ebay) as a result. Good luck!

[@IanScottJohnston]

Nice find on the ASIC....can't see nothing there at the moment though......would have been nice to have.

[@Ynformatics]

@@IanScottJohnston FYI - sourced it (SXC6206AKO/V4 for the E3631) from www.utsource.net/

[@andymouse]

This will be fun, you did say you wanted " Meaty " !...cheers.

[@piercetkwong]

Single character on the right said Broken. Left said Main Board open ..... (scribbled) and below said no display.

[@douro20]

Is it traditional Chinese or simplified?

[@piercetkwong]

@@douro20 simplified

[@andrewsweet43]

Holding down the "Display Limit" button for a couple of seconds while powering up the unit performs a self check. Maybe you sould try that

[@wetering]

Page 98 of the Service Manual gives you the details of the self-test. With that you can check the communication with the front panel.

[@dav1dbone]

The three pin ICs mounted on the heatsink, might be worth checking those since the unit has seen prolonged use?

[@IanScottJohnston]

Thyristors and LM317/337, they are okay at the moment but certainly worth looking at after the digital side is operational.

[@alpcns]

All I can offer is a new hammer... ;-) but it's an interesting repair. Thanks Ian!

[@IanScottJohnston]

I hope it doesn't come to that.....:-)

[@gerrysweeney]

Hi Ian, I have fixed a few of these PSU's by the looks of it I would be looking at the main processor to start with. The display board has its own 8051 based MCU, the power-on reset where the full display lights momentarily is the display processor initializes and looks correct to me. Removing the Display from the PCB can be a pain, I have a number of these PSU's so if you want me to test the display so you can eliminate it I will be happy to do that, its easy enough to test when you have a working PSU. Also, make sure you study the schematic, the grounds are not where you would expect them to be, and typically there is opto isolation between the digital and analog sections, this allows the GPIB port to share earth ground with other equipment.

[@IanScottJohnston]

Cheers for the offer of testing the display Gerry, hopefully i won't have to bother you...... Right now I am all over the cpu etc, so far everything is checking out IO wise, but I have a couple parts on order from RS we'll see where that takes me. Great fun!

[@gerrysweeney]

@@IanScottJohnston your welcome, good luck with the repair

[@TKomoski]

Luckily you have a schematic for this power supply, Ian would you have a quick look at the encoder. I have the E3631A and the encoder works intermittently. Shahriar from TSP did fix it but didn't show what he had done video TSP #108. *Cheers*

[@PeterRidge]

Open the encoder, clean out the old grease that is interfering with the contacts, and put it back together.

[@TKomoski]

@@PeterRidge Thanks

[@TheDefpom]

You can dismantle the encoder, clean it, increase the context tensions and put it back together, I did that in one of my videos fixing a similar supply.

[@TKomoski]

@@TheDefpom Thanks

[@IanScottJohnston]

As luck would have it I have a few 24PPR encoders with the same footprint, so if I get that far I'll probably replace it. For now the existing one is back together.

[@pigrew]

I look forward to the conclusion. The instrument can do a more complete self-test if you hold down any key (except Error) for five seconds as you power it on. Have you checked all of the power supply voltages (especially the MCU rails)? I'm not convinced the main MCU is doing anything.

[@IanScottJohnston]

The complete self-test does nothing more than the normal power on self-test. The power supply voltages are all pretty good.

[@BjornV78]

Maybe start with the basic, and check if the transformer is okay, and if all voltage rails are present. I guess that there is a 5V rail missing, which controls the IC's.

[@IanScottJohnston]

All power supplies (there are quite a few) are fine on both the earth referenced and floating sections of the main board.

[@BjornV78]

@@IanScottJohnston , i hope that there are no damaged ic's on the board, that maybe not widly sold to the public. Good luck anyway, looking forward to your next video.

[@inhnamtranlam9779]

Is this PS good or not? I intend to buy one, but I have seen a lot of video fixes for that PS.

[@stevec5000]

You need to soak the fuse carrier in LimeAway or CLR. BTW, what is that weird purple instrument on the workbench?

[@IanScottJohnston]

It's EEZ-BB3 power supply.

[@artursmihelsons415]

Is there CPU clock? Is there some activity on ROM reading? Are all power lines for chip ok? This project looks very great and interesting. Sad, that there is no information about how this fault started because that will get some clues where to dig.. But looking at resoldered parts, looks like someone blow it up.. Waiting for next part! :)

[@IanScottJohnston]

I am working on a Part 2 video today actually, the Cpu clock, reset and the power supplies are all looking ok. The addess/data bus all look active, no shorts (can usually see this on a scope).....plenty more to test though.

[@artursmihelsons415]

@@IanScottJohnston These are good news, at least some activity.. Agree, this project needs lots of testing to find out why CPU is sitting in some initial loop and what event it's waiting.. Lots of things may be wrong: bad serial shifter, bad output transistors (maybe it trys to set up initial output and can't do it, causing loop), opamps, corrupted ROM.. Anyway, it will be cool to figure it out and bring that power supply back to the life.. :)

[@barryforever]

I'm facing Unreg issue. Observations : 1) Self Test pass . So that's a relief . 2) No errors reported. 3) OVP : 25V, OCP : 4A 4) Display Limit : 25V , 2A 5) Output On with 25V,7A Mode : a) Setting 0V, 0A- Recorded (DMM) 42.62V b) Output Off : Holds 42.01V (DMM) , takes close to 3-5min to 0V 6) Tried to change voltage and current setting on PS, But cannot change anything. DMM records 42.62V Do you know how to fix it ?

[@IanScottJohnston]

If you look up one of my other Agilent Power Supply videos on YT there's one that had similar output voltage fails similar to yours. They are all very similar in design so good luck!

[@johnas2004]

240V? How very 1980s!

[@M0UAW_IO83]

UK Mains is 230V and has been since 1995, it was 'harmonised' with Europe to make the import and export of electricity from and to the continent easier (good thing as we're net importers of electricity because successive British governments have been utterly crap at updating our electricity generation capacity)

[@IanScottJohnston]

243VAC measured here (NE Scotland)......it's sometomes a concering when plugging in primarily 230VAC gear......LOL!......Yeah, don't much care for British/Euro politicians......useless twats!

[@SpeccyMan]

@@IanScottJohnston You got that right. A bunch of muppets the lot of them.

[@MartinE63]

The link to France, established in 1961 was 100kV DC, the replacement in 1986 is 270kV DC. The voltage the consumer is supplied with, and ‘harmonisation’ is totally irrelevant to the energy transfer capability across the inter connectors. It’s now 30 years since the UK electricity system was privatised. Apart from 7GW of legacy AGR nuclear, 5GW of coal, 3GW of pumped storage and 1GW of hydro (circa 16GW total) ALL the other generation in the UK, around 65GW, is totally new build post 1990, so in excess of 30GW of gas, around 2GW of which has already closed, 24GW of onshore and offshore wind, 13GW of solar, and 1.2GW of nuclear (Sizewell B in 1995) The supply voltage for the UK was defined prior to harmonisation as 240v +/- 6%. After harmonisation 230v +10/-6%, the super grid transmission and distribution networks are still run at exactly the same nominal voltages they always were and UK consumers are still supplied at a nominal 240v. 240V +/-6% is 225.6-254.4V 230V +10%/-6% is 216.2-253V Facts, as ever, are all that really matters

[@jonka1]

Here in Mid Wales it's 245V and it rarely drops below 243V

[@M0UAW_IO83]

@@MartinE63 You're absolutely correct that import/export voltage is irrelevant, my bad, I don't quite know what I was thinking but i meant to say it was for import export of goods and somehow got completely screwed up in the middle. Even more embarassing given where I work, there's a bloody big poster on the wall downstairs showing details of just that.