Many hams have had problems with the arcing in the plate tuning cap. Heath
addressed the problem with a higher voltage cap.
I had the same problem with my SB-220 in 1978. What I discovered was a relay
sequencing problem. The single relay switches the antenna between TX and RX but
also removes the cutoff bias from the tubes. I found that the contacts on my
relay were removing the bias and putting drive to the amp BEFORE the antenna
was transferred, thus the amp was putting out full power without an antenna for
a few milliseconds, just long enough to cause the arc. The arc may be a
parasitic but most likely its just a result of having no load.
I solved the problem by installing another relay, using the bias contact of the
original relay to energize the new relay and have it switch the bias. This made
it impossible to put power out of the amp BEFORE the antenna was switched.
I believe many of the SB-220 capacitor arcing problems are caused by this
situation.
Greg
---------------------------------------------------------
Greg Chartrand - W7MY
Richland, WA.
DN-06IF
W7MY Home Page:
http://webpages.charter.net/w7my/
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