hp 6286a supply

[Joe R.]

At 12:27 AM 1/17/06 +0000, you wrote:
>> 
>> At 01:04 PM 1/13/06 -0700, you wrote:
>> >
>> >
>> >
>> >I have found in a number of supplies the front panel adjustable pots  
>> >open up or the wiper go south. This will make the output go to max.  
>> >Another problem is small electrolytic caps in the voltage control  
>> >circuit going bad. Often, blindly shotgunning all the small caps will  
>> >make things work for another 15 years (sorry Tony...).
>> 
>> 
>>   Don't apologize. There's nothing wrong with that approach. If one cap has
>> failed, it's mostly likely that the other's aren't far behind.
>
>This is a constant flamewar in the UK vintage radio magazines...
>
>I would be careful shotgunning parts. Firstly that you don't introduce 
>more faults (either by using unsuitable capacitors or mis-connecing 
>them). Secondly that you don't cause problems by changing a capacitor in 
>a timing cirucit and having to re-align things). 

   I think both of those would apply without having to state the obvious.
   

>
>And of course you do need to be able to trace the fault 'properly' if 
>changing the capacitors doens't fix it.
>
>My expeireince with old HP instruments (mostly from their decktop 
>calculators) is that capacitors are not a major source of problems.

    That usually true of HP gear but it's a BIG problem in Tektronix and
other brands. I've found that I can't leave a Tektronix scope of the 465
vintage powered off for very long without them developing shorted
capacitors. I had a Tek 465 that I only used occasionally and everytime
that I turned it on (several months apart) it had a new capacitor problem.
That went on for over two years till I finally gave up on it and found a
newer scope (Tek 2445). I suppose the difference is due to the different
type/brand of caps that HP and Tektronix used.

   FWIW I like the Tek scopes better than HP scopes but the HPs hold up
better.


    Joe