The manual can be found here: https://www.hafler.com/pdf/archive/DH-220_amp_man.pdf The DC offset and bias are covered at the top of page 11. It's been a while so I don't remember the details. diyaudio.com has a few threads on the subject. There is some good info there. For what you are replacing, I don't think values will change. Only make adjustments if the DC offset is over 50mv if I recall correctly. And if the amp is evenly warm, no real need to play with the offset. Too high a bias and you can burn out the transistors. I disagree with the manual about the settling time. It's more than a few seconds. I was also told later that two calibrated MM's make the job easier.