Bias questions

[Ampaddict]

Forgive me for stupid questions but...

1) Remove the backpanel. You'll see three (four) jacks above the fuses.

2) Set your multimeter to mA and plug your black probe into the black jack and the red to one of the red jacks.

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp. Why volume to zero and what if it's NOT at Zero? Also does it matter if a guitar is plugged in?

4) Now switch it on and read the bias current from your multimeter. Adjust it to the proper value by turning the bias pot which is accessible with a little flathead screwdriver through the hole in front of the red jack.

5) When finished, turn off the amp, install the fuse and repeat the same
steps for the other pair(s) by using the other red jack(s) and removing the other fuse(s). Can I just hit the amp on standby, put the fuse back in, take the next one out and proceed?

 

[MARK2C]

3. Any signal to the power amp may skew your bias results and show a fluctuation while trying to bias.
If you have signal from the guitar and try to play while biasing with the OT shunt method, you will hear a bad fizz.

5. Turn the amp fully off for safety and take your time.

 

[Hey_bert_whtcha_doin_bert]

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp. Why volume to zero and what if it's NOT at Zero? Also does it matter if a guitar is plugged in?

You have to zero the masters because your setting the "idle" of the power tubes, you wouldn't adjust the idle on a car at full bore would you?

2nd question I don't know.

 

[duesentrieb]

2nd question I don't know.

Just shut the amp off. Its for safety.

 

[Ampaddict]

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp. Why volume to zero and what if it's NOT at Zero? Also does it matter if a guitar is plugged in?

You have to zero the masters because your setting the "idle" of the power tubes, you wouldn't adjust the idle on a car at full bore would you?

2nd question I don't know.

So if I Biased 'em w/ the volume up a tad the Bias is wrong. Is this correct?!

 

[duesentrieb]

3) Remove the jack-corresponding fuse from the fuse holder which is located on the backplate, turn volume controls to 0 and make shure a load or speaker is connected to the amp. Why volume to zero and what if it's NOT at Zero? Also does it matter if a guitar is plugged in?

You have to zero the masters because your setting the "idle" of the power tubes, you wouldn't adjust the idle on a car at full bore would you?

2nd question I don't know.

So if I Biased 'em w/ the volume up a tad the Bias is wrong. Is this correct?!

Yes and no. If no signal was applied - same bias. That changes if you apply signal (play guitar). Should be same if you didn't.

 

[Ampaddict]

So if I Biased 'em w/ the volume up a tad the Bias is wrong. Is this correct?! [/quote]
Yes and no. If no signal was applied - same bias. That changes if you apply signal (play guitar). Should be same if you didn't.[/quote]

I'll check it again. It's still out of the chasis. Thanks guys