Jea48,
Thanks for your concern. I seem to be blessed with regards to my VT100. I ran it for a month on new input and driver tubes without even checking the bias. When I did do the biasing I found the 160 volt measuring points to be within the specified tolerance of +/- 20 volts of 160 volts and 20 volts of each other before I began to adjust anything and they remained that way after all was done. So I didn't have to swap the tubes around willy nilly. The tubes I ordered were not matched but the two sections were very close to each other for each tube. It took me over 2 hours of iterations on the resister pots to get everything within spec. I didn't measure any points not mentioned in the biasing instructions. After I biased the power tubes I went back and checked the voltages for the input and driver tubes again. The 60 volt points had drifted to 61.5 v. I turned them down with just one pot in each channel and the other voltages stayed within tolerance. I finally checked the power tube biases again. You can see why it took such a long time.
In spite of everything being within tolerance things can still fail. That is not only the nature of tube equipment but virtually any machine created by man. Tube gear just fails more frequently. I bought the amp 6 years ago and it is at least 20 years old. I figure I've had a good run with it. If something fails before I sell it I'm prepared to spend some addition money to replace it.
According to Alice Trillin, wife of famous humorist Calvin Trillin, “Money not spent on a luxury once considered briefly is the equivalent of a windfall income and should be spent accordingly.” I'm in her camp.
Thanks for your concern. I seem to be blessed with regards to my VT100. I ran it for a month on new input and driver tubes without even checking the bias. When I did do the biasing I found the 160 volt measuring points to be within the specified tolerance of +/- 20 volts of 160 volts and 20 volts of each other before I began to adjust anything and they remained that way after all was done. So I didn't have to swap the tubes around willy nilly. The tubes I ordered were not matched but the two sections were very close to each other for each tube. It took me over 2 hours of iterations on the resister pots to get everything within spec. I didn't measure any points not mentioned in the biasing instructions. After I biased the power tubes I went back and checked the voltages for the input and driver tubes again. The 60 volt points had drifted to 61.5 v. I turned them down with just one pot in each channel and the other voltages stayed within tolerance. I finally checked the power tube biases again. You can see why it took such a long time.
In spite of everything being within tolerance things can still fail. That is not only the nature of tube equipment but virtually any machine created by man. Tube gear just fails more frequently. I bought the amp 6 years ago and it is at least 20 years old. I figure I've had a good run with it. If something fails before I sell it I'm prepared to spend some addition money to replace it.
According to Alice Trillin, wife of famous humorist Calvin Trillin, “Money not spent on a luxury once considered briefly is the equivalent of a windfall income and should be spent accordingly.” I'm in her camp.