Could anyone help me confirm the cause of failure in this circuit

[romeoleung]

Thanks for the inputs, this is the whole diagram I have and that’s all, this channel has 6 power tubes but on the diagram there’re only 4 shown, so some part of this diagram is missing.
View attachment 1318828

This is an Audio Research power amplifier schematic, isn't it？

 

[nb63]

Oh, dang! Yeah. I missed that. That's a manufacturing and service nightmare ... and not good for the reliability of the resistors either.

Tom

The back side is difficult to access, might have to remove the board

 

[nb63]

This is an Audio Research power amplifier schematic, isn't it？

Yes it is.