I'd say it's more likely to be a problem with a transistor in your output stage than with a capacitor.
Why do you think it's a capacitor?
And with my background in transceivers, I would have to agree with Steve.
for 100+ Watts out, chances are there are 2 devices in the output stage. One or both
are probably short cct (or close to) between collector and emitter.
Can you tell us what the part numbers are on the 2 output devices?
and take a sharp well lit photo
cheers
Dave