Fixing a benchtop power supply I built 37 years ago

This one is still my favourite benchtop power supply, but I broke it recently, so it needed some repairs.
This was also a good opportunity to try out my new Gochifix 3 in 1 scope meter.
Review on that meter coming soon
Amazon link for scope meter, and discount code:
amzn.to/3VN7klZ
Discount code (25%off): 25MathRS

[@DanteEsGrande]

"It's got a loud fan" Sir, thats a jet engine.

[@markm0000]

That fan is louder than most cars engines idling.

[@scotttovey]

That's what I was thinking. Revving up for take off.

[@runforitman]

I do love how timeless your designs are decades old but I could see you making them today

[@runforitman]

(this is a genuine compliment I like how they look)

[@matthiasrandomstuff2221]

yes, I'd probably make it like that today. But I wouldn't hand letter the front panel now.

[@1873Winchester]

@@matthiasrandomstuff2221 I really like the hand lettered front myself

[@Hoaxer51]

@@1873WinchesterI was admiring how neat the lettering was, if I could print like that, all my stuff would be hand lettered.

[@jeremiahbullfrog9288]

@@Hoaxer51 You can, go slow and practice. It will seem extremely boring but resist the urge to rush through the letters.

[@CharlesKiblinger]

A few audio dropouts at 5:52, 6:01. But I wouldn't blame you if you didn't re-re-re-upload at this point!

[@matthiasrandomstuff2221]

I didn't have time to go through the whole video again. And if I'd somehow fixed those, sony vegas would probably have failed somewhere else. Some video projects in vegas are just cursed.

[@robertsteel3563]

@@matthiasrandomstuff2221 I bet Sony made your copy of Vegas cursed! 💀

[@prgnify]

@@matthiasrandomstuff2221 Sony Vegas in general is sometimes cursed. Actually, scratch that - Video Editors are sometimes cursed. I never met a single professional who doesn't complain about crashes. From FinalCut to AVID to Kdenlive or DaVinci resolve.

[@TheAnimystro]

@@matthiasrandomstuff2221give davinci resolve a try some time - it’s free and really really good

[@maximthemagnificent]

That meter is a lot less expensive than I was expecting; eager to see your review on it.

[@genericuserid7283391]

Oof, no one knows tour video performance stats better than you do, but I'm surprised to see you call a sub 10 minute video long! Im sure many people would like them significantly longer, but im sure you've studied your audiences sweet spot.

[@rr85]

I have no idea what any of that meant but i watched and thoroughly enjoyed every minute of it

[@BigEightiesNewWave]

With his skills, I'm surprised there was never a wooden, Blackberry phone.

[@jamess1787]

In B4 next months video.

[@rr85]

That we know of

[@smug_cat1]

Not enough time

[@KerboOnYT]

Nice wooden case and that multi tapped transformer is really handy. I still have a small bench supply I built around 1990. It's fancy because I splurged on a Radio Shack metal enclosure. 😊

[@SupremeRuleroftheWorld]

this video did not help in the slightest in making me feel less old. Thanks Matthias.

[@EeekiE]

That’s one handsome multi-meter

[@EitriBrokkr]

Curious to see what it is

[@egw]

@@EitriBrokkr It's a 'Gochifix 3 in 1 scope meter' (according to the video's the description 😉)

[@wissamkadamani]

I've been delving into switched mode power supplies, and this is just so much simpler and more digestible. I feel nostalgic although i was born decades after you made that power supply. You're an inspiration man! Keep it up!

[@JonnyDIY]

Too cool although I dont understand much of this. Cant believe you and your bro were doing all this back in the 80s! Thats awesome 👍

[@Rouverius]

Yeah, that power supply has been many videos over the years. Thanks for teardown. And glad to see you got it running again.

[@johnford7847]

Thanks for re-uploading. The audio glitches were tolerable but it is much easier to follow in your re-edit. Thanks for sharing.

[@Dukey8668]

Electrolytic caps get a bad rap because cheap junky ones do have a tendency to fail, especially those from the capacitor plague. But in my experience good quality older electrolytics last a very long time.

[@1pcfred]

It depends how the capacitors are used how long the're going to last. Caps fail in modern equipment because we use them pretty hard. A SMPS may switch at hundreds of kilohertz. That's tough on capacitors. Plus we don't design as much headroom into equipment anymore either. In the past 200% was standard and now it's more like 20% If stuff specs at all. Cheap chargers usually can't do half what they claim.

[@TheMixmastamike1000]

This video was awesome and I’m excited for the meter review. 👍👍

[@locke3141]

Was going to ask what scope meter that was! Glad to see you’re going to do another video featuring it

[@MarcSacksZA]

Watching this kind of video after watching too much electroboom has me flinching

[@3v068]

You are making me want to build one of these. I use a car subwoofer in my room, mainly because its much more powerful than home subwoofers that are AC driven, and less expensive than buying a dedicated indoor subwoofer with an amplifier. A power supply like this could actually let me run the woofer much harder than I can now using a computer power supply for a DC voltage.

[@express375]

No clue of what any of that means, and yet we still watch.

[@Blu3B33r]

Really interesting and my first time seeing a power supply from the inside. Thanks for sharing! I've been using an ATX breakout board as a cheap alternative for my DIY projects 😄

[@osgeld]

older metal can caps of that era are generally fine. Older than that and you start getting into paper ones then yea, newer than that where they started making micro sized and early SMD caps like the late 80's get sketchy. 90's are generally OK then in the 2000's they went to crap again in all sizes

[@1pcfred]

Capacitor plague was caused by industrial espionage gone wrong. Someone stole an electrolyte formula but it didn't have a stabilizer in it. It was missing the secret ingredient. Then they started making it and selling it cheap and a lot of manufacturers bought it and used it. So the failures were widespread. Only a couple brands weren't affected.

[@Petertronic]

Love your PSU. I recently bought a faulty TTI lab power supply from ebay and the fault was exactly the same type of rectifier!

[@MCsCreations]

Pretty nice power supply, Matthias! Awesome work! 😃 Some day I'm definitely going to build something like that! Stay safe there with your family! 🖖😊

[@MazeFrame]

0:26 That is a lovely fan spool!

[@markm0000]

That was cool to hear. Like an old computer waking up.

[@matthiasrandomstuff2221]

Now I just need to find a few more ASMR sounds like that to make a video about it :)

[@MatchaBarnes]

Really appreciate the info in this. Never thought about building a powersupply. but definately seems do-able considering you've done it 3 times.

[@TrentR42]

My understanding is that ATX power supplies are the easiest way since all the wires are color coded

[@1pcfred]

I thought about building a PSU when I got tired of dead batteries experimenting with electronics. That happened when I was a broke kid at 15 years old. I couldn't tell you how many PSUs I've built since then. A few dozen. Every electronics project needs a PSU.

[@12345NoNamesLeft]

Thermal paste is mostly zinc oxide or titanium dioxide in a petroleum carrier - Very much the same as the white diaper rash cream.

[@artursmihelsons415]

Nice looking power supply! 👍 Don't worry about audio dropouts.. No need to re-upload video another one time.. Best thing with older and simpler power supply's is that they live longer than modern ones.. 😂

[@BlacksmithGen]

I was surprised the capacitors were still ok, though i might have been tempted to swap it out regardless.

[@1pcfred]

The caps are only dealing with line frequency. Plus they're quality caps. Still as good as the day they were made.

[@P_RO_]

Some of the caps you can get today would die before these old ones did, so I wouldn't change them unless needed. Not everything from China is junk but some electronic components from there are; gotta know what you're getting.

[@1pcfred]

@@P_RO_ The one capacitor Watthias has is a Rubycon. They're the best capacitors made.

[@FishyBoi1337]

Lol, I thought my yt client was tweaking giving me the same notif so many times. Happy to give another view, though!

[@Falney]

The dmm went beep the same time I took a measurement with my calipers. My immediate thought was "Wait? My Calipers don't beep."

[@lwilton]

Cheap (for the time of manufacture) caps tend to go bad over a few decades or even a few years. Decent caps can last many decades. I've got a 1960s Lambda power supply on my bench that still runs just fine. I've never opened the case or replaced a part other than the voltage adjust pot. I've never needed to.

[@JohannSwart_JWS]

I find it funny that 6.3V is one of the most common filament voltages for tubes, but your transformer does not have a tap for that. OK - 5.8V + 12% boost gets you close, but not exact.

[@matthiasrandomstuff2221]

The rheostat would adjust for input voltage, so for a typical input voltage, the rehostat would probably be centered, and put it half way between boost and no boost. Also, those voltages are measured with the cheap volmeter I had at the time, and the line voltage we had at our house. Our last house had 126 volts, which was not that typical.

[@SauronsEye]

Are you getting better at this KZbin thing, by getting us all excited in anticipating your next video or was that an accidental cliff hanger, in announcing the 3 in 1 review in a future video? A bit like the old Saturday morning, Flash Gordon, movie theatre serials that cut off just before some perilous ordeal, seemed likely to befall our hero and you had to come back next Saturday to find out what happened.

[@jimsvideos7201]

I like the Tivoli vibe.

[@matthiasrandomstuff2221]

Probably pre-dates that company

[@dieterjosef]

Usually I watch this on Marco Reps' channel but he has mostly newer stuff. And it is also way over my head.

[@1pcfred]

That's a pretty simple PSU. The transformer steps AC down and the bridge rectifier converts AC to DC and the capacitors smooth the rippling DC into a smoother DC.

[@oskimac]

esr in parallel caps is improved vs one single bigger cap.

[@charlesurrea1451]

Looking at all those taps, looks like an octopus shoved into a jar! I's a really nice Supply you've made there. So what, third time's a charm?

[@senorherrponas5445]

Nice sliding case cover, I kept rewinding the video to admire it. Will probably try to copy its design in the future. How did you make the front lettering? It's paper or some other material?

[@matthiasrandomstuff2221]

Hand lettered on paper, then run thru the laminating machine at my highschool, back in '87. didn't expect it to stay nice looking for this long!

[@Gunbudder]

3:10 that grease may be worse than an air gap. you might want to do a bit of testing to see (or just look up thermal conductivity for that type of grease). some greases actually insulate better than air. i always keep a roll of a sil pad tape for exactly the situation you were in where you don't have or can't find any thermal compound (or thermal epoxy). sil pads are often more than good enough for hobby stuff like that power supply. and having it in the roll is awesome! its a bit expensive, but its like having a roll of copper tape and a roll of aluminum tape. buy once, cry once and you will probably never use the whole roll lol

[@ahbushnell1]

Often a circuit breaker is not fast enough to protect semiconductors. Good video.

[@johnpearcey]

It is if protecting against over current, since it takes some time for the heating to take effect and break the semiconductor. Particularly something like power diodes.

[@ahbushnell1]

@@johnpearcey He has a transformer which adds impedance so that limits the heating.

[@jimthesoundman8641]

Nice oak case.

[@spacewolfjr]

I thought we agreed that you'd wear a Tyrolean hat when doing product reviews?

[@toferj7441]

OMG! I *love* the sound of that loud fan!! Gives me the ASMR tingles!! I could listen to that ALL DAY! I'm not even kidding.

[@kalebhollingsworth7255]

It has a loud fan A literal airplane takes off out of your basement

[@gordslater]

0:30 sounds like that fan is driven by a huge conveyor/drive belt system :)

[@1pcfred]

Sounds like that fan's bearings have seen better days. But at least you know when it's on.

[@imqqmi]

Are you sure the meter updated when using the new capacitor? It appeared the same as the old caps but if the ripple is so low the scope meter doesn't trigger and doesn't run in free running mode the last capture is of the old caps.

[@matthiasrandomstuff2221]

it went from flat line to that waveform, so I'm pretty sure its not the old waveform

[@maxpowersam]

I’d be interested for you to either send the caps to mr Carlson and get him to test them, or….for you to do a review of some of his projects (like his cap tester)

[@atzefatze]

...how about an (light)-indicator for the breaker that shows status? (green / red led)

[@RoadTo19]

I wouldn't mind a video explain oscilloscopes, divisions, how to read/use them, etc. If you have already made such a video, share a link please???

[@matthiasrandomstuff2221]

"divisions" are just the grid lines. 1 volt per division means each grid line is 1 volt. There, explained it, no need for a video.

[@BruceChastain]

I'm sort of confused, I thought we were close to the same age, but I was 4 in 1986 so, yeah, you look young.

[@spacewolfjr]

I think he was born around 1970.

[@20kilovolt]

Maby a LM317 adjustable three-terminal positive-voltage regulator is a nice cheap part to regulate voltages 0 to 37 V 1,5 A to experiment with see the datasheet for more information.

[@paulfrizzell31]

👍

[@markm0000]

That’s a really neat power supply.

[@Ice-Qube]

Any chance that you make a power supply build video? I am looking for one but making one similar to this would be way cooler! I know some electronics but mostly digital stuff. Would love one like the first one you showed with Current limiting.

[@matthiasrandomstuff2221]

if you have to buy all the parts, its cheaper to buy them in a box already assembled to be a power supply.

[@bqdavis1]

I think I have a tube tester in the garage somewhere.

[@KelikakuCoutin]

Thanks for the content. Keep up the good work. בס'ד

[@SamJantz]

That is the biggest resistor I've seen lol

[@jimbarchuk]

Be grateful it wasn't the thrid upload.

[@johnalexander2349]

Fluke used to make a graphical multimeter. Used to. :-(

[@eh42]

I think I figured out the schematic for your rectifier, test: You are feeding AC via a current sense resistor into the AC terminals on the rectifier with nothing / no load on the DC terminals, right?

[@ecsyntric]

random or not, i’m here

[@wizrom3046]

That transformer physical size looks about 30 watt, maybe 35 watt. So it really should NOT be pressed to the 6 amp range, ouch. For continuous use that's about a 12v 2.5 amp supply.

[@EVILGRINCH101]

I think there are still some audio issues @6:02, but not that bad.

[@ron827]

Did you ever get into ham radio? 73, K0FTB

[@pete3897]

SECOND re-upload (third upload)

[@TheBitKrieger]

[@dadabetic]

what's the pc-term for "mad scientist" these days?

[@TrentR42]

🎉 Comment for increasing engagement!

[@elektro-peter1954]

Thanks for not replacing the caps! i always hate to see someone throwing out perfectly good original caps that have lasted for lots of years. I feel in such cases it doesn't do the device a favor, the new cap might even break sooner than the old one would have. I see the retro guys recapping their C64s and I just think: why? I never saw one of the 3 big electrolytics bad in all my time repairing C64s

[@MrTurboturbine]

For real.

[@bradydennis9572]

I just thought you were cursing. Lol

[@RossTheGenMan]

I was watching the video earlier and it suddenly cut off and said it was no long available.

[@matthiasrandomstuff2221]

rectifier is dimensioned to handle the short. Just after a minute it got too hot, I think

[@1pcfred]

SMPS capacitors go bad because they are subjected to high frequency. That high frequency causes internal heating of the capacitors.

[@matthiasrandomstuff2221]

That power supply rarely even gets warm, and its usually in the basement, so it doesn't even get warm in the summer.

[@sacriptex5870]

hey Matthias teaches us to build one

[@matthiasrandomstuff2221]

start with an old tube tester from the 1950s... :)

[@sacriptex5870]

@@matthiasrandomstuff2221 ahhhaahah

[@BScatterplot]

I'm certainly no expert, but is there any chance the caps are only bad at higher voltages? IIRC, multimeters only measure caps at a couple volts.

[@matthiasrandomstuff2221]

I also measured the ripple current left after filtering, and that was the same as with the new caps, so I would assume they are good at higher voltages too

[@md51236]

I wish I was smart.

[@Petertronic]

The update rate on the scope-meter looked sluggish compared to the Zotek one. Also don't like the style of the digits. Await review with interest!

[@matthiasrandomstuff2221]

yes, it is indeed kind of slow, and the digits are hard to read at a distance. It's got other shortcomings too.

[@paintsey]

Comment engagement crew!

[@16ats]

5:51 there is a slight glitch

[@scruggs.jonathan]

Man, how old are you?

[@riz94107]

Hey now those of us around the same age take exception to this :)

[@scruggs.jonathan]

lol. I guess he just has a baby face. I would've thought he was no older than 40, but I don't think he made that when he was 3. Well, maybe... 🤣

[@guillaumeemualliug8220]

Subs at 0'18'' say "rock"while you say "rack", I believe. Sorry for the i-Tüpferlritterei ;)

[@TheWangbolizhong]

😅😅

[@aseq2]

This video sounds a lot like this video for the Rockwell Retro Encabulator to me: kzbin.info/www/bejne/iImtfJeeZrCNZtk

[@matthiasrandomstuff2221]

Perhaps to you it does!

[@deepakk1347]

so you are old!

[@spaz_chicken]

Unfortunately there are still audio glitches around the 6 minute mark for me

[@jamescollier3]

maybe you can get your money back?

[@spaz_chicken]

@@jamescollier3 I don't have a problem with it (or the original upload for that matter), I was just letting him know.

[@lifeai1889]

When a digitally controlled buck boost module is so cheap there's no practical reason to not use one of those in combination with atx pc power supply

[@jojoposter]

It you need fine output adjustment maybe, but it will also be noisy. Depends on what you want. Plus, why replace what still works?

[@1pcfred]

You can even adjust the output of an ATX supply. But it isn't ideal. All of the components in the PSU are sized for a specific output. But if you change the voltage reference voltage the output will change too. The control IC is just going to track the reference.

[@1pcfred]

@@jojoposter you can add more filtering to clean SMPS up a lot. What's in a PSU is like the bare minimum. Another layer of filtering helps. I've seen a substantial improvement adding a Pi filter on the output. From OMG to not tea bag.

[@lifeai1889]

@@jojoposter its not like the supply in the video is noise free it is not linear regulated,just a simple rc filter

[@lifeai1889]

@@1pcfred yes, with simple switching power supply there is always a 431 zener diode and by replacing the resistor you can tune the zener voltage (now the cheaper supply sense the voltage from auxilary winding though) but the downside is its allot less efficient if you want large voltage range and the voltage cannot go too low (but yeah indeed under 3.3v is rarely used) the cheap buck boost module also have percise current limiting which is very handy to test leds and to not destroy the circuit if something goes wrong

[@tastemystuff]

Okay smart guy