[R-390] Orange Drop Caps vs Film Polyester Axial

[Bob Camp]

Hi

Let me throw another wrench into this.

There is an enormous knock off industry out there. I have very little concern for the stuff that Mouser or Digikey sell. Stuff I get at a ham fest, who knows. Stuff from the auction sites - worth looking at very closely. I've received several batches of parts that didn't look quite right, and they were indeed not right. 

Bob
 
On Apr 25, 2013, at 1:31 AM, Charles P. Steinmetz <charles_steinmetz at lavabit.com> wrote:

> Drew wrote:
> 
>> At issue is the self-healing action, which consists of momentary short circuit between the capacitor's "plates", followed by vaporization of a small portion of the very thin metal layer.  It would seem that at some low voltage this would not occur, and so we might use caps rated for, say, 800V in a typical receiver application where the voltage encountered is much lower.  Would this approach have merit?
> 
> My own tests, and those of others whom I trust, indicate that metallized film capacitors exhibit unacceptable self-healing events at impressed voltages of 200Vdc or less, regardless of their voltage rating.  On the other hand, unacceptable self-healing events have NOT been observed at impressed voltages of 50Vdc or less with metallized film capacitors rated at 50Vdc and above.  So, I use metallized film capacitors in SS designs but not in tube circuitry.
> 
> Best regards,
> 
> Charles
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