Contact ARC for a manual.
Biasing This amp is easy and Dangerous. I have 30 years experience in electrical/electronics. This baby can bite, my hand hurt for 2 days. I think it is 575 Volts inside the case. Be sure you know how to use a multimeter, and you have good 1000V leads. A nice Fluke or equiv. If you are not sure, send your amp in to ARC and they will do it for you. I sent mine in for new tubes and they found a problem in the turn on circuit and fixed it for free.
Call ARC first and they will tell you how to ship to them.