Bias adjustment in an amp....need advice from the techs

[Audioman00]

I have an older model Yamaha receiver (one of the better ones) and I noticed a couple of little riostats or potentiometers right next to the output transistors (seems to be one for every channel) and wondered if this is the bias adjustment? or maybe a gain level? I dunno, I was hoping to catch a tech on this site and find out if it can be beneficial to adjust these in any way. Thanks for any advice!

[JoeE SP9]

They are probably level controls. Bias on solid state gear is usually not adjustable. On tube amps it is almost a requirement. When output tubes are replaced the bias is adjusted to provide equal current flow through the tube pairs.

[poneal]

There are quite a few EEs that frequent the site and will be able to provide you with more info. Regards, Paul.

[Jace]

without looking at the circuit, i couldnt tell you. it could be a great many things. what model of receiver is it?

-Jace

[Beckman]

http://www.tnt-audio.com/clinica/bias_e.html

[dave_bullet]

Try post at
www.audiokarma.org

The people there will almost certainly recommend you get a service manual rather than play... but there is a vintage Yamaha following there - if your amp is in that league there might be someone who can give you instructions.

I wouldn't recommend you play and see how it goes - you're likely to make it worse without a service manual.

David.

[Audioman00]

I blew it up shortly after posting this....ha ha... I decided to turn the bias all the way up while it was on..lmao and BANG!! dead yamaha... man I was dumb