Amp / Tube questions

[LPguitarman]

Ok, in a previous thread, I posted issues with my son's amp. He got it back from the shop, put in (3) new Pre-Amp tubes. He is still getting a crackling noise. We think it may now be the Power Tubes. He said one of them sparked yesterday while he was playing. Needless to say, he is afraid to turn the amp on again because of the spark.

 

My questions:

Does this sound like a power tube issue?

If he gets (4) new 6L6 power tubes "matched", does he have to have the amp re-biased?

What exactly is re-biased?

What happens if he just sticks the new tubes in the amp and starts playing?

 

Need some quick answers if possible.

 

Thanks, Santo

[Guest Farnsbarns]

That amp is either fixed bias or self bias, either way, no biasing has to be done. This is actually not considered desirable and there is a bias mod that can be done allowing proper biasing.

 

A perceived spark from a valve could be a number of things, I'd certainly be changing the valves and I think you'll probably fix the crackle too. However, a crackle can often be a dry/cold joint.

[LPguitarman]

That amp is either fixed bias or self bias, either way, no biasing has to be done. This is actually not considered desirable and there is a bias mod that can be done allowing proper biasing.

 

A perceived spark from a valve could be a number of things, I'd certainly be changing the valves and I think you'll probably fix the crackle too. However, a crackle can often be a dry/cold joint.

Thanks for the reply. So we don't have to do anything except put in new tubes? I assume the "bias mod that can be done allowing proper biasing" is optional since the amp is either fixed bias or self bias?

[Karloff]

Go online @ peavey. Should be able to download manual. Should say if it's fixed. Which I'm sure it is like mentioned. In that case it best to get tubes that are matched.

[Guest Farnsbarns]

Thanks for the reply. So we don't have to do anything except put in new tubes? I assume the "bias mod that can be done allowing proper biasing" is optional since the amp is either fixed bias or self bias?

 

Yes, the mod gives you more control but not necessary. Peavy built it without a bias adjustment.

[LPguitarman]

Yes, the mod gives you more control but not necessary. Peavy built it without a bias adjustment.

Thanks Again.

[LPguitarman]

Go online @ peavey. Should be able to download manual. Should say if it's fixed. Which I'm sure it is like mentioned. In that case it best to get tubes that are matched.

Thanks.