I recently picked up a used SVT CL and I can only get one of the bias to turn green. The right side one will only go red or nothing. I can hear it hum like crazy if I go to far one way or the other. I bring it back to red and then turn it till the red light just turns off.
My question is how do I know which tubes are bad? I have groove tubes in it now and I just bought a pair of Sovtek 6550we for it. The groove tubes say sovtek on them, so they should be the same?
sounds like you have unmatched tubes on the side that only does red. unfortunately, it's not enough to have a pair that match. you need to match them in triplets. the good news is you can use those new sovteks if you can get another one that matches them. and it doesn't sound like you need to replace both triplet sets.
they have to be tested in a tube tester for plate voltage and transconductance, whatever the hell that is the place you bought your tubes from might be able to help you out with that.
I swapped all the tubes around and the bias lights, after the new adjustments are the same. Green on the left and the right one will only go red of off. I even swapped the driver tubes around.
The only thing that I noticed is that with my gain about 3 I had my master up at 7 1/2 pushing my marshall 810 and I thought it should have been a lot louder than it was. It was loud, but I thought 7 1/2 would be really loud. This is when I discovered the bias lights and began to investigate why only one would go to green.
If you buy your tubes from either the tube store or tube depot the bias point is marked on the tubes and in the future you can order just one tube at the same bias point if that is all thats needed.
the place you bought your tubes from might be able to help you out with that.
