I've got a friends fl-2100b that came from e-bay. It has had allot of experimental mods applied apparently to end oscillation. The thing seems ok until you get the drive up to where you are putting out about 200W, then the output (loading) cap arcs. There shouldn't be high voltage present since the antenna is presenting an almost perfect match without a tuner. I have my own fl-2100b that works perfectly on the same antenna, so I have experience loading these amps up. The amp was sold as having oscillation problems, but I'm not so convinced that is the problem. It has the original Cetrons still as well so I think it should have been fairly stable in stock condition.

Any ideas how the voltage is getting so high on the loading cap? The cap that blocks plate voltage from making it to the tank seems ok and the rf choke to ground is still intact so I know that DC plate voltage isn't present.

My initial plans are to put the amp back as close to stock as I can get it by removing the triple series resistor parasitic suppressors and then going from there.