> It could very well be the plate blocking cap, especially
> if it is undersized for that power or not even rated for
> RF use such as the TV doorknobs.
Not much chance of that. It is a self-testing component.
If the plate blocking cap is dissipating hundreds of watts
it would explode or go up in flames in a matter of seconds.
It is not value critical, there is barely a difference in
output tuning when values as low as a few hundred pF are
used on 160 meters in amps with a reasonably high operating
impedance, let alone on high bands.
If we just take a few moments to actually look at the
impedance change at the anode as the blocking cap is
changed, we see how unimportant the value really is in
operation.
I remember when a buddy and myself were visiting K8KAS and
he had a 100 pF blocking cap in his 160 monoband amp. We
laughed and poked fun at him for something so silly. He got
all red-faced and said he misread the part value.
When he replaced it with a 1000pF cap the tuning barely
changed, the loading didn't change at all, and the amp ran
exactly the same power. I went back home and looked at the
impedance change at the anode and learned my lesson.
73 Tom
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