B52 212 - Are Bias Instructions the same as B52 100?

[Jecarroll7]

Working on a 212, tried to bias it following instructions for a 100 (SS setting with amp meter across fuse holder tabs) and a grid resistor on an output tube smoked.

May just be coincidence but thought I would check. I've also heard there is a bias mod for this amp that improves stability?

[The Dude]

I see no reason why that shouldn't have worked. Possibly you have a bad tube. I would use clips on the fuse holder for a solid connection. Make sure the meter is set to read current and not voltage. I can't speak to the bias mod. I've not had a problem with the existing hardware.

[Jazz P Bass]

The schematic can be found here.
B-52 Pro Audio AT212 100W Combo INFORMATION PAGE

Did you remove the fuse when you where attempting to measure the overall current draw of the amp?

[Randall]

What is the function of the diodes between the cathodes and plates of each pair of 5881s?

[Enzo]

Regular old flyback diodes.

[Randall]

And D8 is to divert flyback voltage thru R95 15W?

No, that's wrong. Cathode current flows thru R95 during normal operation, and flyback voltage is shunted thru D8 when conditions reverse, such as shutting off the amp. Is that correct?

[Jazz P Bass]

The flyback diodes are there to help protect the output transformer from abnormal spikes.:ie: open load on the secondary: severly overdriven output stage.
(unless they fail shorted )