HELP , More problems with Bias

Richard, What tubes are you using? I have two Rev 3 SE-40s and had to modify the bias circuit in order to get Svetlana 6L6's to bias correctly. You cen find more information at
http://golden_tube.listbot.com/cgi-bin/subscriber?Act=view_archive&list_id=golden_tube Cheers, Dan

I don't want to give the impression that it is common to have biasing problems when switching brands of tubes. It is actually rather rare. Most tubes of the same type can be changed for one another with no problems.

Hello Brucel483 Your advise on bias is welcomed. I have a Anthem amp1 and it came with ElectroHarmonix EL34's. I would like to change them but with what you advised Richardzerambo I will have to look at my manual to see what SF recommends. Richardzerambo I hope you get through this.

To answer to your last question about what happens if you play it in this condition. If the bias current is too low, i.e. the reading is set lower than .635V, the sound will be distorted. But no harm will be done.
If the bias current is too high as in your case, the tubes will be running hotter than normal. This would shorten the life of the tubes but not likely cause any damage to the amp.

Hello again. I would first switch the tubes from one channel to the other.
If the problem moves with the tubes, you have a tube problem.
If it stays on the same channel, you have an amp problem, or a compatibility problem with your tubes and amp. I would suspect an amp problem at this point since the tubes biased correctlty in the other channel, assuming the tubes are reasonably matched.
When you are adjusting bias, you are adjusting a DC voltage applied to the grid of the tube to set the amount of DC current flowing through the tube when it is idling (no signal). Sometimes the range of bias voltage available is not great enough for a particular type of tube. If the amp was designed with one brand of tube and they were later changed, this can occur. Theoretically, all tubes of a certain type, for example, all EL34's, should require about the same amount of bias, but this is not always the case. Replacing the tubes with those recommended by the manufacturer would take care of this problem.
If the problem stays on the same side, the circuit that controls the range of bias voltage is likely defective, and would require service.