Harrison High-Stability Lab PSU with Oven Stabilized Voltage Sense - HP 6102A

[saturation]

6112a is a good supply, its the ancestor of the 6114a, high precision power supply; IIRC about 20ppm accuracy.

[robrenz]

Very nice!  I bet it is something very minor or nothing wrong at all. These supplies were designed to survive stupidity.

[calin]

Supply is here ... of course took it apart before turn on so I respect the rules 




So far I did just a brutal brushing and blow cleanup but more cleaning will come. Side panels are soaking now ...


Attached are some picture of the PSU working .. Yeah I found the issue .. the power switch is gone. If you look careful there is a red wire that ties the power straight into the transformer primary. And look @ that .. last call i could find stuck on done in 6/75 and 10.000V read 10.052 ish .. damn that is good. I did not touch anything in terms of calibration .. just cleanup, some measurements to see what is wrong , check some voltages here & there to make sure it does not blow up and voila ... Its alive !!! and actually kicking some butt. I want to see a PSU from today doing this after 40 years.


Attached some pictures ... running with the guts spilled on the desk ... enjoy.

[calin]

Restoration complete .. i gess I can declare this one a winner.


In final I had to replace the power swtch and the main filtering electrolytic cap. That was gone and was causing some serious ripple on the output. After this and a calibration with the tongue at the right angle everything works as it should. I did some measurements with the tool I have @ home and after 2 days of continuos on on 10.000V set .. I barely can see any drift. See in the picture bellow .. that is after 2 days ON .. the meter flicker between 9.99999V and 10.0001V sitting moslty on spot on 10.0000V. Too bad I do not have a  GPIB interface to log some data from my Fluke so I get an nice representation for the drift. But anyways this seems damn stable .. I can say the most stable PSU I have .. not bad for an oldie
I also did some differential noise measurements using my Owon 7 using the poor mans differential/math approach @2mV. literally cannot see any ripple in the output ; I guess I need a Tek scope with 5uV/DIV to see anything .. good enough for me .


Couple of pictures bellow of the after restoration

[robrenz]

Very nice job   A real thing of beauty

[saturation]

  Kudos, too.  Great job restoring this precision PSU.