[Central-Electronics] 20A ten meter issue. C81 as a suspect?

[Stan McIntosh]

Hello all,

While playing with crystals and outputs, I could only get a tiny signal out
on 10 meters, and we're talking well below a watt.  Although I wondered if
using the 4th harmonic of 40 meters might be taking things too far, I
started looking at C81.  Output increases with turning the screw clockwise
(to still well under a watt) without going through a peak.  If these are
compression trimmers, could they be subject to silver-mica disease, so the
effective maximum capacitance is not what it used to be?

Any other thoughts?

Regards,
Stan
KD4BTH