capacitor aging claim

[Eric Smith]

>>    On 10/07/2010 03:15 PM, Richard wrote:
>>> Yeah, but this isn't what occurs when you just power on the device.
>> Actually, it is.
> No, it isn't.  The part you didn't quote is where the other poster was
> saying "apply increasing voltage gradually".  That's what you do when
> you reform a cap.  Its *not* what happens when you turn on the power.
> Otherwise people wouldn't need reforming circuits.
>

The specific context was a device that's been powered off a relatively 
short time.  The oxide has only deteriorated a small amount, and not to 
less than the working voltage.  Powering it up, at the working voltage, 
will do some reformation, and will no damage the capacitor.

I never said that this procedure was applicable to capacitors that had 
been powered off for a long time; in fact, I think I specifically said 
otherwise.


I described a different procedure for capacitors that haven't been 
powered for a long time, which involved limiting the current into the 
capacitor.  Limiting the current has the effect of not allowing the 
voltage to increase beyond what the capacitor can handle (assuming that 
you chose the current limit appropriately).  This is actually much 
better than ramping the voltage at a constant rate, because the 
capacitor make take longer for reformation during some points in the 
process than during others.  We saw that with some capacitors in the PDP-1.

Despite that, it is still the case that reformation is what is occuring 
in both scenarios, which is what I replied "actually, it is" to in the 
quote above.  It is the same electro-chemical process; you seemed to be 
claiming that it was not.

Eric