Re-biasing after replacing output tubes

[Budweiser]

Bought my Marshall jcm2000 dsl50 over 2 years ago & decided to replace all the tubes as it has started to buzz louder & louder. I put all JJ's in, but haven't tried it out yet. I never knew the EL34's have to be re-biased? Learn something new everyday. So getting a tech to do that tomorrow, then have piece of mind. Then I can hear the difference between JJ's & what the amp came with. Hoping I'm pleasantly surprised.

 

[metlking]

Re: Re-biasing after replacing output tubes

Sweet.....the DSL50 is a great amp in my opinion. I had one, sold it. Wish I hadn't! You can bias it with just a multi-meter, no special tube adapter bias tool what-so-ever. More amps should be set up that way! Look on Youtube on how to do it!

 

[Gearjoneser]

Re: Re-biasing after replacing output tubes

Good to see you posting. Yeah, Jeff's right. The DSL is perhaps the easiest amp to bias because of the external bias points. I think they're under a shield on the back, if I recall correctly. If you don't have a volt/ohm meter, you can get them for $5 at Harbor Freight. Then find some info on the net regarding volts/amps etc.

EL-34's usually sit around 35 - 38mA as a median safe operating range.

 

[Surgeon]

Re: Re-biasing after replacing output tubes

The two previous post are great. However, I'd like to applaud your decisison to bring the amp to a tech when in doubt. Too few do this and end-up with problems.

 

[Budweiser]

Re: Re-biasing after replacing output tubes

Glad I brought it to a tech. The bias was set very low. He said marshall factory setting is low so the tubes last longer. Now she's all set up at 30 per side (whatever that means? Lol) and I can't wait to try it out tomorrow at practice! He said I'm gonna have way more power now & a better tone. Wish I did this years ago. I've been playing a low reving amp & didn't even know.

 

[Surgeon]

Re: Re-biasing after replacing output tubes

Rock that thang!

 

[Scott_F]

Re: Re-biasing after replacing output tubes

Glad I brought it to a tech. The bias was set very low. He said marshall factory setting is low so the tubes last longer. Now she's all set up at 30 per side (whatever that means? Lol) and I can't wait to try it out tomorrow at practice! He said I'm gonna have way more power now & a better tone. Wish I did this years ago. I've been playing a low reving amp & didn't even know.

Just having access to bias test points will not allow one to bias properly. You've got to know how many volts are hitting the power tubes. Weber's site has a very quick and easy calculator for figuring the set point out.

I bet it sounds great now!