[Boatanchors] Ceramic disk capacitors

[shoppa_boatanchors at trailing-edge.com]

"Dave Maples" <dsmaples at comcast.net> wrote:

> All: I need to replace a group of ceramic disk caps in a transmitter.  It's
> the usual...500 volt, .005 MFD disk ceramics.  What's your favorite source
> for these?
>
> Thanks,
> Dave WB4FUR
>
>
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>

The classic answer is "Mouser" for this medium-voltage disk ceramic
stuff.  The one semi-gotcha is that many lines of disk ceramics no longer
have the ".005 MFD" value but do have the ".0047 uF" or "4.7 nF" standard
value (while some do still have the oldish standard value and some still
have both, whether they're the same part with differing marking is
irrelevant.)  And of course modern parts tend to be smaller diameter
disks with maybe a little bit more thickness at this voltage.

Mouser, Digikey, etc., have higher voltage disk ceramics too in the
1 and a few kV range that you'll be needing for a transmitter.

Many 50's or 60's vintage rigs that used micas for coupling or bypass
or neutralization can often (but not always!) use modern disk ceramic
insteads. At the 100W power level and above I'd be wary of working
entirely on voltage specs though and start thinking about dielectric
dissipation (power).

If you are picky about disk ceramics that do not look "new" but instead
look "period" there is Antique Electronics Supply and a few other places
that cater to those who restore tube receivers.

My personal preference for medium and HV disk ceramics is Mallory.

Tim.