Thanks, super helpful response. I've unplugged the amp, and will wait until I have a multi-meter to check bias before I power it up again. From your advice it appears I can't really rely on a technician to do the bias check, as it really should be checked on a regular basis.
Any multi-meter you would recommend?
Apparently there is no Service Manual for the Luxman MQ-88se. I contacted Luxman USA and they sent me the following:
Bias Procedure for MQ-88uSE
WARNING * SHOCK HAZARD * This procedure should be performed by a qualified technician only.
Main body, just in front of LR output transformer, there are 3 points where you can insert tester leads.
The center point is for the ground, left and right points are for Left + RightKT-88 test points.
Please insert tester lead in the center point and left point, then using an insulated Phillips head driver, adjust the left potentiometer as needed.
The value should be 0.48V (480mV) +/- 5%, please adjust if needed.
Repeat procedure for right points and right potentiometer.
It is good practice to check the bias on the other set of KT-88’s to be sure they are within 5% of the specification.