[Boatanchors] Navy RAL Filament Voltage: Solved

[David Harmon]

What Rob said....


73

David Harmon
K6XYZ
Sperry, OK


-----Original Message-----
From: boatanchors-bounces at mailman.qth.net [mailto:boatanchors-bounces at mailman.qth.net] On Behalf Of Rob Atkinson
Sent: Monday, March 19, 2018 12:13 PM
To: Rodger Singley <wq9nsc at live.com>
Cc: BoatAnchors QTH <boatanchors at mailman.qth.net>
Subject: Re: [Boatanchors] Navy RAL Filament Voltage: Solved

> A lot of the “mica look alike” caps that are of a high value are 
> actually the old wax paper types in a flat pack that look just like 
> the mica construction from the outside.

That's one of the reasons why I shotgun all of them out.  There's an arcane, complex and difficult to remember way to tell the real micas from the micamolds but pigs will fly before I ever commit it to memory.

> Most failed micas do so because of silver migration which can occur 
> when there is a high DC differential across the capacitor but they 
> normally don’t develop the high resistance leakage common to older 
> foil/paper types sealed in wax.

Another reason why I shotgun out the old micas. Depending on the circuit they get replaced with either ceramic or polypropylene film.

Rob
K5UJ
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