[Amps] Weird Alpha problem

[rick darwicki]

I was working in my 76 converted to a 78 QSK and fine tuning the choke. I was getting 1100-1500 watts our cover off into a dummy load. For some reason I doubled the plate coupling cap size and put the lid back on.
 
on 40 and 80 if I keyed it the amp stayed in TX, then I noticed it was taking off, freq varied as I tuned the load/tune. Nothing would stop it short of unplugging the drive coax. There was a bit of arcing in the bandswitch. I shut it down.
 
This morning I get nothing out on any band. There is HV and plate current increases with drive, but no grid current or RF output when tuning. I can see the exciter output on the RF meter and the antenna is switching/keying.
 
If I key it on 10M there is no output, but if I put it on my 160/80/40 vertical thru the Nye tuner buttons, the amp takes off. Moving the bandswitch doesn't stop it but load/tune changes the freq. If I switch back to the beam the oscillation stops.
 
I has an MFJ-259B on the plate choke and accidentally pushed the Alpha on button trying to slide the amp back, which sent the HV into the MFJ, naturally it fried.
 
Suggestions and ideas welcome, posting the MFJ on ebay, "Parts or Repair" already heard.
 
Thanks


Rick, N6PE
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You can't fix stupid, but you can elect it."