#1241

[@thrillscience]

I love the way you're getting "for parts only" equipment to work again!

[@sleibson]

My favorite supply for the last 50 years. Had one on my bench at HP. Bought one 10 years ago and have it on my bench right now. Very handy for 2- and 3-supply situations.

[@artursmihelsons415]

That was amazing! 😂👍
After 2 years of shelf life, HP power supply was finally justified as fully functional..
Great video!

[@mr1enrollment]

I have had very good luck with many "repair" instruments. I look for dead units since mostly they are the easiest to fix. Yes sometimes you find something that just works, Congratulations!

[@leandrolaporta2196]

Those meters looks gorgeous

[@uni-byte]

I have it's smaller brother the 6235A. It also needed a repair but it was just a capacitor replacement. Got it for $50 CDN.

[@qzorn4440]

wow, nice power-supply, back in the hp USA days with nice faceplate. 😎 thanks.

[@johnwest7993]

I always like to fix equipment with repair tags written up like that. It means the repair person was not a tech, just a flunky following repair procedure documentation. It was in for recert and tripped a few milliamps below rated current so it got rejected because it didn't meet spec.

[@paulcohen1555]

The linear, variable, tracking +, - section is a golden addition for dual polarity op amp experiments.

[@MikeFikes]

I have one of these and it behaves exactly the same way. This is indeed just an internally-set constant current limit (which you can tweak for the +20V and -20V outputs via R6 and R26).

[@vincei4252]

I have the same power supply. It's one of my favorites of many PSU's that I own. I replaced the blown power indicator with a bright -white- green LED.

[@johnjohn-ed9qt]

The 6200 supplies are awesome. This is a great score for a good price. I have several 6200 series for different purposes, though my primary on the bench today are an E3634A and a 66312A, for automatic testing (curve tracer? what do I need that for? I'm in no rush). I also use a GW functional knockoff of the 6236B. I will note that the current dropout here is not a crowbar. It is foldback for the 6V, and a hard limit for the +/-20V, the difference being that a crowbar (traditionally implemented with an SCR) shorts the output to ground to protect from overvoltage, and only resets on power cycle or explicit reset. Foldback is load sensitive voltage reduction, and doesn't require a reset operation, as when the load drops sufficiently , the supply will comply again, as with hard current limiting (constant current for linear loads). R6 and R26 set the +20 and -20 limits. Using the current load, once you exceed the setpoint, the potential will go to near zero, as that is what the load forces, since sufficient current is not available. If you tested with a resistor, say 20 ohms, and set the supply to 12V, you should get 0.5A, give or take, and 10V.

[@M1America]

I have one of these. I like the smell it makes when I use it haha. Yep, mine works the same. Not very useable for most things but it would be nice for validating analog circuitry over a range of supply voltages. No constant currant and when used for things like 12v its only half an amp.

[@JoseHernandez-md8tv]

What a nice example of a bad diagnostic. Nice load design, found the link on the other comment and will soon rebuild it for my own, thanks for that.

[@lelandclayton5462]

This happens all the time at my job. Wish the techs would open a manual or at least look at a datasheet.

[@plainedgedsaw1694]

Or a front panel...

[@scottdrake5159]

I _love_ these. I have this variant, as well... nigh indestructible and easy to service. It's silly to want more, but I would dearly love another one to live next to it.
Funny thing: around the time that HP bought Harrison Labs, the lore is that HP engineers hated servicing them because of their alleged complexity (this was mid 1960s, I guess, so I can't fault them too much.) They didn't come in often, but required thought when they did, because of their designer's ahead-of-their-time feedback loops. Sort of the "alien technology" scenario. This specimen looks like a more recent sample, and of course they now have a reputation for being pleasant to troubleshoot now that the designs are well-known and became standard in most supplies.
I couldn't find the original lore on Harrison that I remembered... it's mentioned a lot on the web but I can't find the original boat anchor history site that had the HP engineers actually mentioning their head-scratching work on the Harrison designs, which were really, really advanced for their time, apparently; one reason HP bought Harrison was because Harrison had developed some of the earliest switching supplies, as well as the most reliable and stable early transistor supplies. I'd love a link to a site that could match that description if someone knows of it.
And, of course, the 60s/70s HP badges are pretty.

[@danharold3087]

HP put the schematics for a lot of their old equipment online. Not sure where.
Have one of these. Mine let the smoke out. Have not opened it. Suspect a electrolytic blew.

[@IMSAIGuy]

www.ko4bb.com/manuals/174.62.104.144/HP_6236A_6237B_Operating_and_Service_Manual.pdf

[@ddowlingau]

A dual tracking supply is great for op-amp circuit testing. It looks like the analogue current meter is reading a bit low on the +/- 20 V range. This might have confused the tech testing the unit.

[@PapasDino]

Now you have two pieces of gear to return to the "nice lady" at the goodies store so they can sell them as working!

[@IMSAIGuy]

I've already given them a few items. I think I need to keep this one as it was the supply on my bench when I was a real designer decades ago. One of those perfect designs. It just does what you need it to do.

[@wonderbars36]

Have 2 of these, a 6200B (unfortunately...that one has a failed lower tap on the transformer), and the 40V version of that one. Can't remember the model number of that one. Anyway one of the 6236Bs I had wouldn't regulate at all and was DOA. If the meter just pegs to max, chances are that's what's up. There's a reference opamp, a hard clamping 7.5V zener in the back that burns a crapload of heat, and the 3 regulating opamps for the +5 and the bipolar 20V outs. Both the 20V ones were blown in my one unit. One can replace those ancient TO-99 1558s in there (those are getting ridiculously expensive for what they are) and just shove a TL071 in its place and you're good to go.

[@Embeddedtronics]

I have same PS bought off eBay for $40 some years ago. Don’t use it much since no adjustable current limit. Still works great though.

[@victorman2227]

Such cool devices, great find

[@fredmitchel1236]

Good job..and just replace the knob.know.,
I thought you might check the ripple...but the meter looked steady...
I have that same meter...single supply...I know it good for 100 VDC...
Nice active load....

[@t1d100]

Getting the deal-of-the-day is never disappointing. Calling out the technician by name and making fun of him? = un-cool, dude. You should edit out that part of the audio.

[@rfdave3980]

You fixed it ! Wow you win the golden screw driver award. Have you done a video on your homebrew load tester?

[@IMSAIGuy]

czcams.com/video/OlqymCSZ4Ek/video.html

[@markgreco1962]

Love the hp repair videos

[@DonzLockz]

Had to laugh at you being sad it's not broken!😄

[@lmamakos]

Looks like the panel meter measuring current on (at least) the -20V range was incorrect. Your load showed 500mA, but the panel meter was closer to 450mA. If when testing he ran it up to 500mA on the panel meter, it would have likely shut itself down since the actual current was higher..?

[@IMSAIGuy]

No, I don't think so. any test lab would not trust the device under test. they would make measurements from the outside. There is a simple resistor adjustment inside the supply to set the meter. I should adjust it.

[@frankowalker4662]

I love the look of the front panel.
Move along folks, nothing to see here. LOL

[@stephaneshm3043]

hi
there a rifa capacitor to be change near the transformer.
my best power suply !

[@tannerbass7146]

Wow you're missing exactly the same knob caps as mine 🙃

[@Forensic1Man]

Hello! Are you getting these electronic equipment projects at " Excess Solutions" in San Jose, CA?

[@IMSAIGuy]

no, that store closed. read the description

[@SaLaGaDH]

It's great that the power supply turned out to be working, but $60 is a bit much for it

[@IMSAIGuy]

wow. where do buy these for $60. I'll buy more

[@andymouse]

Hahaha, classic ! bugger all wrong with it it was current limiting right where it is supposed to !...cheers.

[@KD0CAC]

Good for you , not so good for us ;)

[@FulvioGa]

Very lucky!

[@thermionic_emission]

Could have been an intermittent problem. They are the worse to troubleshoot.

[@Jyaastn]

OpAmps are Happy if that power supply are fix

[@EssArrB]

Not so much RTFM but RTFP - Read The Front Panel!

[@terrygains8327]

Hi, T I Nguyen here. Did I get any messages?🤣

[@fredflickinger643]

I would take it off your hands for $60 plus shipping!

[@sbelectronicaindustrial6652]

👍👍...!!

[@1shARyn3]

PS ammeter is miscalibrated

[@IMSAIGuy]

a bit low, maybe I'll go tweak it

[@byronwatkins2565]

I have a single 0-20 V I'll trade you for it :)

[@satyawanphougat]

Hello from india

[@IMSAIGuy]

nice user name