Bogner 101B Class A issues

[ademus]

Posting this for a potential buyer for my 101 B as it has this problem. I have the post cached as I cannot find it on the Bogner forum.

So I am reposting it here, I hope Fat Tony doesn't mind.

 

I bought a my XTC 101B new in 2004. I loved the amp and really liked the sound in Class A. There were times when we'd

be in band rehearsal and I would see my tubes red plating badly to the point that the amp would start cutting out. I had left it in Class A

the night before and forgot to switch back to Class AB. Long story short, I would end up ruining a quad of tubes in 2hrs.

 

I searched this forum and found the possible solution of swapping out the 2/250ohm bias resistors to 2/ 270ohm resistors. I ordered

2 new Dale 270ohm 50watt resistors off of ebay for $4. They arrived this morning and I installed them in about 30 minutes. You don't need to remove the PCB board, just unscrew the washers that hold the two resistors in place and unsolder the old pair and solder on the new.

Class A red plating is solved. jon_cf was one of the members that suggested this mod, so thanks.

 

Anyone with Class A red plating issues NEEDS to do this swap. It's not the tubes that need changing it's the components causing the problem.

I had tried Svetlana, Groove Tubes, and EH and always had the issue in A.