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Re: Reforming electrolytic capacitors (was Re: Sony CPD-1302 monitor -- IIGS cable?)

js@cimmeri.com wrote:

   Very interesting discussion.   So what's the moral of the story?
This kind of harks back to the old argument about whether to leave an
electronic machine on all the time (for a steady thermal state) or not.


In a distant way, but here we are talking about long periods (years)
of idleness, not avoiding the stress of turn-on.


  Eric, on my IMSAI chassis I recently acquired, I thought I would
reform the caps by putting the power supply on a Variac, and slowly
bringing up the AC voltage.   I had a small load on the bus.   I set
the starting AC voltage at 0 and ramped up every 30 minutes by 10V to
finally what resulted in 4V from the 8V supply, ran for 12 hrs, and
upped the AC voltage to give another another 8v supply volt every 12
hrs.   I pushed the 8V supply to 9V (and 16V supply to 17).

   I don't know if this worked or not but the supply is working.


Sounds like a good reforming procedure.  Something similar is often
done with old (vacuum tube) radios.


   Other than the IMSAI and my Apple Dot Matrix Printer (which I'm
recapping) and Imagewriter, I don't have any computer stuff that
doesn't use a switchmode power supply.... and certainly no monitors.


Doesn't matter whether it's switch mode or not--all power supplies
have electrolytics.  Switch mode power supplies have them on both the
line side (high voltage) and on the output side (low voltage).


   So is the moral of the story to occasionally power up your monitor
(or other switchmode device) for an hour or so?    How often is
occasional enough to give the caps their exercise?


If that were done every year or a few, I would not expect any problems
from loss of "formation".  Of course, there's still the drying out
problem, caused by the march of time, the quality of each capacitor's
seal, and the accelerating effect of heat.


    When I power up an old monitor for the first time in awhile, I do
it on the Variac too.. starting at about 90V to give it a softer
start.. then I take it up to 110V.    I don't like running stuff at
120V.. seems too hot and a lot of my stuff doesn't specify 120V as the
nominal voltage... but rather 110, 115, or 117.


This procedure is easy on the capacitors and on the tube filament, but
may actually result in operating modes for the sweep circuits that are
far outside design specs.

I'd call it a wash, and wouldn't bother with the "gentle turn-on" unless
its been more than ten years--and maybe not even then.

As they say, drinking kills brain cells--but only the weak ones.  ;-)
Consider a fast turn on as a way of weeding out "weak" capacitors.  ;-)

-michael

Music synthesis for 8-bit Apple II's!
Home page:  http://members.aol.com/MJMahon/

"The wastebasket is our most important design
tool--and it is seriously underused."