I have this venerable amp that has, honestly, been giving me some serious issues.
It all started with a needle drop from my turntable. Thinking reverse voltage into the amp.
I saw that one of the KT88’s had gone short and replaced with a matched pair.
She ran well for over an hour on first listening and thought all was fine. Fired her up the next day and she didn’t last 5 minutes.
Some nasty sounds inside amp and blown Slow Blow use. Rectifier has tested ok with no scorch marks.
I checked all KT88 and all tubes show 60% on my Heathkit TC2 tester. Bias before failure was steady at around the .550v.
Testing here for 6550 tubes so I’m not sure if that is why I’m getting low reading on those tubes. They are all very close and testing near their limit of good.
I then moved on to the 12AT7’s. All showing a short.
My next move was to open up the unit and start to measure. All components seem ok, even pulled the Can Cap. Wasn’t getting a good read
in situe. No way of testing leakage on caps.
Just replacing the 12AT7’s and firing it up has got me nervous. Two KT88’s already costing $$s.
I know there is a Voltage list that Bob Latino has posted and thought I could go through that with a Dim Bulb attached
Would anyone know if that should be my next plan of attack? Is there a short in a transformer perhaps?
Need some guidance here.
Thanks!!!
It all started with a needle drop from my turntable. Thinking reverse voltage into the amp.
I saw that one of the KT88’s had gone short and replaced with a matched pair.
She ran well for over an hour on first listening and thought all was fine. Fired her up the next day and she didn’t last 5 minutes.
Some nasty sounds inside amp and blown Slow Blow use. Rectifier has tested ok with no scorch marks.
I checked all KT88 and all tubes show 60% on my Heathkit TC2 tester. Bias before failure was steady at around the .550v.
Testing here for 6550 tubes so I’m not sure if that is why I’m getting low reading on those tubes. They are all very close and testing near their limit of good.
I then moved on to the 12AT7’s. All showing a short.
My next move was to open up the unit and start to measure. All components seem ok, even pulled the Can Cap. Wasn’t getting a good read
in situe. No way of testing leakage on caps.
Just replacing the 12AT7’s and firing it up has got me nervous. Two KT88’s already costing $$s.
I know there is a Voltage list that Bob Latino has posted and thought I could go through that with a Dim Bulb attached
Would anyone know if that should be my next plan of attack? Is there a short in a transformer perhaps?
Need some guidance here.
Thanks!!!