TSP #55 - Teardown & Repair of an Agilent E3631A 6V/25V 80W Triple Output Power Supply

In this episode Shahriar investigates a faulty Agilent E3631A 80W triple output power supply. The instrument powers on, display a fully illuminated VFD display before a long beep and dark screen. The disassembled unit reveals a two board construction. After an unfortunate finger burning experience, the fault is traced to pair of extremely hot voltage regulators and Zener diodes. The temperature of these components is measured using a thermal camera and reach 400C! The schematic of the power supply is examined and the appropriate components are replaced. The performance of the unit is verified after the repair.
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[@k3ith1]

"At least I have the wine..." Great videos keep it up. We discuss them at our ham club meetings.

[@Thesignalpath]

Keith Bush Great! :)

[@JustSomeGuy1967]

As a kid I wanted to do electronics...took apart everything but wound up being a paramedic for 25 years...now own an Internet service and tinker in my "lab" as much as possible. Your videos have actually helped me fix a few of my friends electronics by just following your process and reading the diagrams. Your a fantastic teacher...please do more repairs !!! actually, just do more videos ...they are all great Thanks

[@joes5669]

Nice find. I suspect it's been broken for a while considering the VFD is still so nice and bright! Great video!

[@DavidLeeMenefee]

The threshold of PAIN is 125F. Sorry for your pain. Thumbs up.

[@Thesignalpath]

ElectronicWizzard Thanks, it was extremely hot!!

[@thomasboos2470]

I really enjoy these repair videos, please continue with them. One thing I was missing is the soldering job. Some may find it boring, but I am allways interested in how others do their job :), in my opinion the best way to learn how they do it and eventually adopt it to improve own skills. Another part are the tools, which are used, may give some hints what I was allways missing :) great job!

[@twobob]

Solid work. Would love a schematic of the 66309b which is Unobtainium but we can always live in hope...

[@PapasDino]

Super! My comments when troubleshooting a circuit and finding a similar heat related problem are never quite as kind as yours were! And of course the wine makes the burn not so bad! ;-)

[@OrbiterElectronics]

I love the repair vids.. Thanks Shahriar.

[@GiovanniPreda]

Yeah, thanks a lot!

[@DanielKWynn]

Great repair video as always, thanks. I wish you would include the soldering portions. I know from having watched all your videos you think it's tedious, but I know I (and I suspect others) would be interested to see them.

[@EdwinNoorlander]

Great video, Nice. Pity that we have not seen the video of the knob repair.

[@mikeydk]

Repair videos are the best! And even better when they are about power supplies! :D

[@MrMac5150]

Can't wait till the next repair.

[@666alikat]

its pretty good. I feel cheated that we didnt get to see the knob repair. lol

[@Thesignalpath]

666alikat Sorry! It got cut out of the video.

[@davecc0000]

The Signal Path Blog would you please post that short video (fix of the knob)? It covers so many other HP products and would be very popular with your viewers, I think.

[@mattcarlson2685]

The Signal Path Blog Not to mention, repair of an optical encoder moves beyond HP gear. I've got a Yaesu ham radio that needs a similar repair, and the idea behind it may be compatible.

[@idpromnut]

+1 For an optical encoder "quickie" video!

[@jimstand]

666alikat I would like to see the optical encoder repair. I have a bad encoder also..

[@ourplesoop]

Very nice work. Out of all the electronics blogs I sub to, you are the best at analyzing and repairing broken equipment you come across.

[@Thesignalpath]

npnpnp Thank you my bipolar friend.

[@godfreypoon5148]

The Signal Path Blog Ha!! I see Shahriar's finger is not the only thing getting burnt!! "npnpnp", "bipolar friend"... I laughed rather hard.

[@xDevscom_EE]

Shahriar is on fire lately. Well done, well done..

[@jaa93997]

This is why we cant find nice toys on ebay. You have them all!!!!!

[@kennethlyon3829]

That wine glass was something I have never noticed on YOUR bench, and your bench is famous . For me, (a novice) antiseptics and bandages are usually within easy reach. (RHIP?). Good for a smile!

[@rrangana11]

The reson for the 2 wires not going through the connector is to minimize the contact resistance for those 2 wires going into the 2 big resistance.

[@danielpihlquist2664]

Shahriar, awesome video as usual! I have a suggestion for what I would like to see more of: development of some smaller circuit, and go through your thought process. Kindof like the magnetic levitation thing, it was really cool! I dont have any concrete suggestions right now, but maybe I'll think of something, or someone else has some suggestions!

[@gamccoy]

Your finger is operating to spec. It correctly sensed the over temp. I loved the video and thought your thought process to verify nothing else was bad downstream was great. A lot of people are tempted to replace the first thing they stumble upon and end up causing a good part to fail.

[@witeshade]

Man it's lucky you touched the regulator and not the zener diode... seems like the regulator was the cool part!

[@SirBunghole]

Another excellent video Shahriar! My repairs always seem to involve a damaged custom part that is found to be unobtanium and I end up with a parts unit.

[@timthompson468]

Thanks. Good video. I’ve got one of these with two problems. One is the same problem you have with the control knob. I would not have thought of cleaning a rotary encoder. I’ll give that a try. A strange problem is it also outputs voltage when the supplies are off. If I turn them on and set them for zero (via GPIB) they got to zero, but when they’re turned off, they output a significant voltage, even when programmed to 0V. That should be an interesting problem to troubleshoot. I’m glad to hear the schematics are available.

[@MrMac5150]

I love these fix it videos.

[@AmirHakimiRezaei]

Great video as always! would love to see how you did the knob repair though

[@tmc200527]

I remember leaving skin from my finger on a metal can transistor once. Nice repair video. I would have liked to see the knob repair also.

[@zaprodk]

Very easy repair - Congrats on the good result. You forgot to cover the repair of the encoder?

[@TKomoski]

My power supply has the problem when you adjust the control. Is it a mechanical problem or should I buy some contact cleaner? I can live with it because I really didn't think it was a problem until you pointed it out. Thanks for all the great video's, and always keep your electrons flowing and don't get shorted.

[@johnwoods8309]

Thanks for another great repair video Shahriar.

[@JustinAlexanderBell]

Excellent, I always enjoy these repair videos.

[@worroSfOretsevraH]

You have the equipment and knowledge, so maybe you could do some radio transceiver, receiver etc. repair videos.

[@Thesignalpath]

***** I have done RF repair videos in the past. If I come across such an equipment, I'd be sure to make a video.

[@jamisusijarvi646]

i have same problem with rotary encoder in my function generator. Planning to do video of fixing that one.

[@jamisusijarvi646]

and watching this video because i just did get E3631A. It should be working one...

[@robertfenney]

That was a great video. You make troubleshooting look easy!

[@CKOD]

I think you need to check the emissivity setting on your thermal camera. 200-400C and no discolored board or components?

[@kkendall99]

Thanks for the video!! This is another classic example of a real world scenario of a failure. I have learned very much watching your videos as well the ones from Dave Jones. PS. Just drink the rest of the bottle of wine, works every time :)

[@darwinr2278]

Thanks for the video.

[@josebarrientos5191]

Love the repair vids I also wanted to see the knob repair

[@vehasmaa]

I would have expected it to require more repairs then just change zener and regulator... Starting to consider that maybe i should get one of those thermal cameras, even if i rarely have use for one.. Seems handy and in this repair it sure vas valuable tool to have...

[@kristhetrader5029]

As always Sharihar, great video!

[@rubiconjosh]

Great video.

[@Arek_R.]

I cant believe! Most of damaged eq you buy is easy to repair!

[@jusfucksingmeupG]

Great video, but you didn't show us how you fixed the knob?

[@omahacellularsolutio]

Can you tell me where to get your pointing instrument sir? Absolutely love your repair videos!!

[@thomasguilder9288]

Hi, your repair videos are just great! Another very common failure is by the way an optocoupler between the floating logic and the regulator section in these supplys, I've had this one twice! Best regards and good luck for your future repairs! It's such a pity there is no real surplus market in Germany, the companies here are so afraid of their competitors making a good deal that they rather shred ther broken equipment than sell it and import tax is no funat all ;-(((

[@eeramzi]

Great video as always, many thanks.

[@widecast]

I would like to have seen how you fixed the rotary encoder.

[@spagamoto]

Instructive as always. Any theories on why the regulator failed in the first place? Possibly the zener failed first, causing too high an input voltage to the reg?

[@BellA-mf1ti]

looking forward to your next video。

[@jastervoid]

17:29 Those soldered connections look like they're the sense lines for the +25v and -25v rail. Would make sense not to have them on the connector that would introduce a varying (if small) resistance.

[@eldenchang]

Great repair video. You are a master and I always learn something from you. Why is there no model number on your FLIR thermal imaging camera?

[@rysend]

Another good one, thanks!

[@GeorgeGraves]

So what was the fix on the dial? (I assume it was a rotary encoder) Have you already covered that in a past video? Would love to know.

[@quadplay2591]

same here, I need to know how to fix the rotary encoder.... whats the trick?

[@rajk5326]

Great Video mate. Thank you.

[@int2str]

Yupp, the repair videos are great! Thx for posting. More of a beer guy myself, but well done! How do you find these broken treasures on eBay? Haven't had much luck myself....

[@haddaphone7266]

Thank you for the very informative video. I have exact the same power supply (got it for free, not working). It turns ON with one beep and the test display is always ON (all segments ON). I found diode CR13 (seen at timestamp 18:11) shorted and the track connected to it burned. I replaced the diode and restored the track. No short, but still same result. Any suggestion where to check?

[@tuberlook1]

Thanks, nice repair.

[@PlasmaHH]

You definetly should get used to have a first look at stuff with the thermal camera. Saves you from getting burned, and is just very often leading good results. Also in the case of that sram that failed a while ago, I am sure you would have seen it much faster by just having a look with the thermal camera. the ex8 is on my list just in case I ever get rich...

[@ntcarver]

Dennis Lubert you must remember that not all of us have a 1000£ thermal camera. The purpose of these videos is to teach us about repair without instantly jumping to use all the fancy gear.

[@PlasmaHH]

ntcarver I must have missed that mission statement. IMHO you can't really teach repairing. For me these videos are for getting an insight into the thought process of someone repairing something. And the thought process should be "lets see if something is hot" and if that includes thermal camera nerd porn, its better. Everyone who doesn't have a thermal camera will be able to say "oh hey, ok, I don't have the camera, lets see how *I* can look around for hot stuff". If they are not able to do this transfer then its going to be a hard thing to repair anything but the exact same fault anyways. I guess you didn't watch the 100GHz scope video either...

[@Keith_Ward]

ntcarver Apparently it was a complete surprise that it was *that* hot. Considering just how hot it registered we should have heard a sizzle. I often use close proximity with the backs of fingers to find hot spots first or even freeze spray to see what cools/evaporates off the fastest. Nothing like having your fingerprint burned into the top of an IC. At least thermal cameras have come way down from what they used to be.

[@anthonynowlan9765]

Dennis Lubert I saw a russian video, where the guy used thermally printed paper from receipts. Push on ICs and they would darken when hot.

[@godfreypoon5148]

Dennis Lubert Once you've done it a few times your fingers get used to it. It's not that big of a deal. He didn't even properly swear.

[@kentvandervelden]

Great video, really fun to watch the repair. What is the most likely cause for the regulator failure? Sorry if I missed it.

[@Thesignalpath]

Kent A. Vander Velden It is difficult to say. It could simply be aging, this is an old supply with probably many working hours under its belt.

[@Narwaro]

Resistors Do bot blow partially normally. They either burn out or work normally. With increasing temperature (because this is a metal film resistor) the resistance becomes larger and larger. So this resistor almost acts like a constant power device. Funny

[@tiagobelzfinco7465]

Great video!! Where did you find the schematics? Could you please share?

[@woodsettscentral1196]

Great video. Can I have the address of that landfill site!

[@leppie]

Dave must be really jealous of you :D +1

[@MrHamgolfer]

Which FLIR video camera did you use. Looks pretty handy! thanks for the videos

[@hdmalpas]

A hot thumbs up. Ouch!

[@andresdominguez9333]

Thanks for posting again an interesting repair video, and specially for reducing the amount of e-waste. On a different matter, do you read the discussion comments of your channel? I asked there for a video about your favorite (technical) books. Thanks in advance.

[@Thesignalpath]

Andrés Domínguez It is very difficult to keep up with the comments. I try to replay when I can. I'll try to do a book review in the future. :)

[@RogerJonker]

Nice video 450 C ?? This can't be right. No smoke,carbination,melted solder? Sure it's C not F ? .

[@Thesignalpath]

***** Oh yes, it is C! The solder joins were molten. I could have just pulled the component out without a soldering iron.

[@JustinAlexanderBell]

The Signal Path Blog Sounds like it makes desoldering of faulty components easier.

[@superdau]

The Signal Path Blog If just all broken components would behave that way. Switch the thing on, wait a minute, rattle the case and collect and replace all the parts that fall out...

[@rrangana11]

Hi, It is good video. I do had the same problem and I fixed it the same way you did...But what is bugging me is....What is the root cause of this failure in the first place? There must me a reason for them to fail... Ageing is not a problem since it is a semiconductor... Then Why did that Zener and the Regulator failed in the first place... I am suspecting there is something else is bad which caused this 2 components to fail... May be Caps or resistors somewhere else in the board... If it is then it will fail again... Mine was all working fine all fine then one day morning when I turn-on I see this problem.

[@priestblood]

great video as always .did you change the fuse resistor ?

[@FranciKapel]

How did you desolder that voltage regulator. With hot air station or soldering iron with big tip? Did you cut the legs off first? I would love to see that in the video.

[@PlasmaHH]

at 18:56 you can see the IC without the legs in his hands.

[@Thesignalpath]

Franci Kapel As Dennis also pointed out, I cut the pins then hot air to remove the IC itself followed by soldering iron to remove the pins one at a time.

[@martijn4740]

need to find me one of those supplies

[@IDan1109]

did you repair this while you were drunk??:D good video thanks for sharing your knowledge

[@KirkOfBellevue]

thermal camera first next time?

[@bkupiec]

"Power supply inception" :)

[@Electrolab28Ag]

I love your work but something I notice... Alcohol and electricity don't mix. Ha ha. Great job.

[@gacherumburu9958]

👍👍

[@yaghiyahbrenner8902]

7:17 should have used the thermal camera :)

[@user-gv1vc8ey7o]

Hi can you help me for schemetic diagram

[@hansaya]

You should sell those power supply's

[@markoantesic4362]

HI, how did you clean the knob? What kind of knob is it? From which e-bay (UK, USA...) do you buy all this repair treasures? BTW Did you get me PM?

[@Thesignalpath]

Marko Antesic Hi Marko, no I don't think I got your PM. And yes, this was from eBay.

[@markoantesic4362]

The Signal Path Blog Can I send you a e-mail (if so on which address)?

[@Thesignalpath]

Marko Antesic Sure, it is [e-mail].

[@Fusionx916]

How much did you pay for it?