New to Ampegs

[Dave1966]

I have tested the FS to death, its definately OK, as is the cable although it looks very much the worst for wear. I have also tested all the caps, resistors and pots. Swapped the tubes as I dont have spares. No change. Maybe the caps read ok, but are "weak"? I get avery slight effect for a split second when throwing the switch, but it goes away immediately. I don't have any voltages on the schematic, what should I expect on the "B" node?

Thanks again for your help!
Regards

Dave