[time-nuts] HP 5328 PSU nightmare...

J. Forster jfor at quik.com
Sun Sep 13 16:00:24 UTC 2009


I generally use an external HV PS and bring the unit up slowly, roughly 50
VDC per step and let it sit for several hours at each step. Reforming caps
is a chemical process, and does not happen in microseconds.

-John

=============


> J. Forster wrote:
>> With tube gear, one fairly good way to reform the caps is either pull
>> the
>> tubes (label where they came from) or disconnect the filament supply,
>> and
>> then apply B+. You do need to check the schematic to make sure you don't
>> overvoltage caps that would see an increased voltage w/o plate current.
>> Also, cathode bypass caps may never see the reforming voltage.
>>
> Good advice, but leave the rectifiers (80, 5Y3, 5U4 etc.) in their
> sockets :-)
>
> Bill K7NOM
>
>> For solid state equipment, the light bulb thing will limit collateral
>> damage on simple rectifier-filter analog supplies. Switchers are more
>> problematic.
>>
>> -John
>>
>> =============
>>
>>
>>
>>
>>
>>
>>> And vacuum tube equipment using indirectly-heated cathodes:
>>> http://www.cpii.com/docs/related/23/Basic%20Tube%20Design.pdf
>>>
>>> "Operating techniques that are proper for filamentary tubes are not
>>> necessarily
>>> correct for tubes with indirectly heated cathode emitters. In
>>> particular, the opera-
>>> tion of cathode types at reduced heater voltage can be destructive to
>>> the tube."
>>>
>>> Leigh.
>>>
>>> Mark Sims wrote:
>>>
>>>> Be very careful powering up modern equipment on variacs and with light
>>>> bulbs in series, etc.  You go through areas where the bias voltages,
>>>> etc
>>>> are in  the right place to cause serious damage.  Switching supplies
>>>> can
>>>> be particularly entertaining...
>>>>
>>>> ----------------------------------------
>>>>
>>>>
>>>>
>>>>
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>>
>>
>>
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>
>






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