a question for amp builders and modders

[metalmachine]

i heard that you have to replace the film screen resistors in a 5150 before you can do the bias mod. is this true? do those really have anything to do with how hot you can set the bias? i heard it was justr on the older ones. mine is a block letter so i guess it is pretty old.
i am confident enought to unsolder a resistor and replace it with another resistor and a trim pot. but i am not confident enough to start replacing things without proper instruction.

any help is appreciated. thanks.

[glassman]

Re: a question for amp builders and modders

Yes.

5150's technically over-dissipate 6L6s at full signal. I regularly replace them in amps that maintain the stock non-adjustable bias as well. The stock set up eats tubes with no positive audible effect. In fact, replacing the stock 100 ohm/5 watt resistors with 1000 ohm/5 watters really brings out the punch in the amp and makes the tubes last a lot longer. It is major surgery to get to them and you shouldn't even consider doing it yourself unless you know how to drain the caps and have the means of being able to verify that they are drained before you proceed.

[metalmachine]

Re: a question for amp builders and modders

i really appreciate it man. thanks!