Hoffman Amplifiers Tube Amplifier Forum

Amp Stuff => Tube Amp Building - Tweaks - Repairs => Topic started by: aquitania on January 19, 2015, 03:29:25 pm

Title: Dead 6L6 ??
Post by: aquitania on January 19, 2015, 03:29:25 pm

Hello all,
Have a twin reverb here.
I was getting some noise issues with it a while back. Still have them.

I've discovered that one of the power tubes has a much smaller bias current than the other three. ~11mA vs 33mA for the rest. Also it seems to be running a lot hotter than the other three.

Anyone seen these symptoms before?

(No I don't have a spare set of tubes to throw in, I'd have to buy some)

Cheers
Dan

Title: Re: Dead 6L6 ??
Post by: shooter on January 19, 2015, 08:21:17 pm

How many miles are on the tubes?  I've seen 2 amps with bad tubes, the funny thing, both guitar guys said there's nothing like the sound of a dying amp (paraphrased).

Move the tube, does the low bias follow the tube?

Title: Re: Dead 6L6 ??
Post by: 6G6 on January 20, 2015, 11:19:42 am

^ What Shooter said.
Swap the questionable one with one that is working well.
Does the trouble stay with that socket or move with the tube?

Title: Re: Dead 6L6 ??
Post by: aquitania on January 20, 2015, 01:59:12 pm

Good suggestion.
The problem moved with the tube.
This tells me the tube has issues and needs a tissue/replacement.
Tells the same to you gents?

Cheers
Dan

Title: Re: Dead 6L6 ??
Post by: shooter on January 20, 2015, 03:10:58 pm

Yup, I'd get 2 if you have the $$s.