Problem on Rowland model2 need help

[Chalitr]

Have somebody here familiar with these amp. I have the problem happen while the amp switch back to stand by mode during normal listening. Preliminary measure found DC voltage at right channel output, which cause DC servo shut it down. However, I just unplug the eletrical cable cord and start run the amp again on the next day and problem has gone. I can play the amp around 6-7 hrs without any problem. However, the problem coming back again on evening with the same right channel. Can sombody here probide me any suggestion on how to check this thing? In the PCB board, I found the 3 adjusting knob (1. offset 2. Biasand 3. Temp). I suspected that the amp is drift out and need to adjust them back to target. Can anyone here give me some suggestion on how to adjust these knob?

Appecaite your suggestion.

Chalit R.