Author Topic: HP 6281A erratic meter movement  (Read 298 times)

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Offline ledtester

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HP 6281A erratic meter movement
« on: June 09, 2019, 03:27:47 am »
Hi,

I got an HP 6281A power supply from a university surplus sale for just a few bucks, and when I turn it (a cold start) on the meter behaves very erratically as seen in this video:



After a while it seems to settle down and start to behave normally, but it still can glitch unexpectedly. Also, when I change the meter setting from 9V to .9V it has a tendency to start flailing about again. Sometime turning the voltage knob back and forth gets it to settle down but not always.

The Aneng 8008 shown in the video is hooked up the power supply's output. It isn't the fastest meter, but it doesn't seem that the HP's meter is showing the real output voltage and that the output voltage is actually rather steady.

Any ideas on where to start looking?

Thanks!

Update: I've attached a photo of the rear terminal strip. The strappings are:

  A3 - A4 - A5 are connected
  A6 - A7 - A8 are connected
  A9 - (-S) - (-) are connected
  (+) - (+S) - A10 are connected
« Last Edit: June 09, 2019, 05:19:55 am by ledtester »
 

Offline wn1fju

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Re: HP 6281A erratic meter movement
« Reply #1 on: June 09, 2019, 12:36:16 pm »
There are probably a couple (or more) potentiometers in the meter circuit to set things like the zero point and the full scale voltage reading.  My guess
is that they are dirty.  Spray some cleaner into them and twist them back and forth a few times (returning to their original point).  See if that helps.
 

Offline Ordinaryman1971

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Re: HP 6281A erratic meter movement
« Reply #2 on: June 11, 2019, 02:18:49 pm »
Clean the range switch as well. You can spray a bit of whatever you favorite contact cleaner is in the round openings in the switch assembly. Switch is between ranges few times and you should be good to go.
 

Offline ledtester

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Re: HP 6281A erratic meter movement
« Reply #3 on: June 12, 2019, 06:46:37 am »
There are probably a couple (or more) potentiometers in the meter circuit to set things like the zero point and the full scale voltage reading.  My guess
is that they are dirty.  Spray some cleaner into them and twist them back and forth a few times (returning to their original point).  See if that helps.

Yes it did help! Thanks!
 


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