How to install BIAS MOD in PEAVEY BUTCHER + Full recap and maintenance tips + Audio review

A Peavey Butcher came in the shop that needed repair. To give this amp a new lease at life all of the electrolytic caps were replaced, installed new output tubes, installed adjustable bias circuitry and installed a better output jack system than the counterintuitive one that comes stock.

Fast forward to the end to hear the amp through Celestion G12T-75's and Vintage 30's mic'd with an SM57

The adjustable bias was achieved by swapping R52 on the power board (470-ohm stock) with a 3K resistor and replacing R53 (47k stock value) with a 10K resistor in series with a 22K mini potentiometer with the wiper and opposite fixed end soldered to the large ground pad on the underside of the PCB.

This is, hands down, my favorite Peavey amp I've heard so far. I really like the simplicity of the design and it was super easy to work on. I think these were very well made and stand the test of time. After all, the circuit design in the preamp is almost identical to a Marshall 2203/2204 circuit.

Enjoy and happy riffing!