#1241 HP 6236B Triple Output Power Supply

Episode 1241
Big red tag says it is broken.

[JoseHernandez-mdtv]

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.

[thrillscience]

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

[wonderbars]

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.

[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..?

[frankowalker]

I love the look of the front panel.




Move along folks, nothing to see here. LOL

[fredflickinger]

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

[terrygains]

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

[mrenrollment]

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!

[artursmihelsons]

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

[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.

[johnwest]

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.

[qzorn]

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

[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.

[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).

[MAmerica]

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.

[lelandclayton]

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

[danharold]

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.

[johnjohn-edqt]

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.

[vincei]

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.

[thermionic_emission]

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