I ended up buying the Ampeg V4BH that I mentioned in another thread. All tube, 100 watts (enough for me), mint condition 2 yrs old. Sounds great, warm, smooth.But this is my first tube head, so I really don't know how its supposed to sound. It has Groove tubes. Are these factory from Ampeg? anyway, I want to take it into a tech for a service and a go through. I was reading about biasing in the owners manual and online. How exactly does a tech bias this particular amp. I looked in the chassis, and dont see any trim pots, or anything. Just tubes and transformers. Will he have to drop the guts down from the chassis? Is there something inside the guts to adjust? Maybe this amp is self biasing? Don't worry, I'm not gonna try this myself, I'm just curious how this is done.