Wow. . a bunch of excellent responses including Alpha even offering the cap
bank as an assembly (I understand there may have been some failures of this
part). Anyway, I think I got some answers and several good options.
Thanks for sharing the knowledge. See you all in the Stew. . .73. . .
Dave, W0FLS
P.S. The cap is a ceramic disc.
-----Original Message-----
From: daraymond@iowatelecom.net
Sent: Friday, December 28, 2018 3:16 PM
To: topband@contesting.com
Subject: Topband: Need for capacitor
Greetings topbanders. . .
While CQing early this morning I began noticing a faint but troubling smell
in the shack. It smelled like over heated wiring or electrical components.
It continued to get stronger as I realized the odor was coming from the
Alpha 99 amp. Indeed, a few moments later it tripped out. I dug into it
this afternoon and discovered a leaky 75 pF/6 kV cap which is one of five
such caps in a parallel bank that is pulled in on the band switch to achieve
tank resonance only on 160m. I have removed the bad cap making the amp
operational once again with the air variable tuning cap making up the lost C
(and there’s still a little C to spare on the air-variable). After some
searching I cannot find a 75 pF/6 kV cap. Mouser does not have anything
even close in terms of the high voltage rating (hopefully I didn’t
something). The closet thing Newark has is 47 pF which I have ordered. I’m
guessing the 47 pF is probably OK but how important is equal current
distribution across the five caps? Maybe I don’t need to be concerned about
it? If I really do need the correct 75 pF/6 kV cap does anyone have ideas
of a source? Replying privately is fine. See you all in the Stew.
73. . .Dave, W0FLS
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