Last night I was re-tuning my AL 572 amplifier on 40m into a 40m dipole but I had the band switch on the 20m band. Just as I saw the reflected power go to 200 watts while tuning the antenna capacitor, I heard a faint "tink" sound. It did not sound like a high voltage arc. Operator Error! If I had the band switch on 40m, the tuning would have been very close to where it should have been and would only have needed touched up.
Now I get very little power out. Can someone please give me some guidance on where to start to troubleshoot this amplifier? I have an understanding of electronics but not vacuum tube based circuitry or failures. I realize reflected power and poor SWR are bad, but I don't know what may have failed.
I have a new set of 4 matched 572s but I am hesitant to install them without some testing first.
The only info I have found on the internet is to check diode D117, but I don't understand why this part would be bad. Any technical help would be appreciated.