The believe the folks at Acoustic Sounds can guide you through this.
JP, I have the instructions for the amp. It is a word doc. How do I send it to you?
You have to take the back plate off. There are resistors at from where you have to measure the voltage. The voltage has to be set at 0.4V on your multimeter by turning the pots. The amp has to be on for about 5-10 minutes before your measure. The speakers have to be connected but all sources have to be disconnected.
It is very simple but you have to be careful not to touch anything.
I went through this years ago when I owned this same amp.
Take a bit of friendly advice. UNLESS you really know what your doing, I wouldn't open this up and start poking with a screwdriver in there.
It is a fantastic amp indeed, but the inability to bias this amp easily made it a non-keeper for sure in my book.