Acoustat TNT-120 Bias and Offset Adjustment

I have a TNT-120 that I've owned for almost 40 years.  I want to check and possibly adjust the bias and DC offset of the amp, but I cannot find any info on how to do it.  The TNT-200 is well documented, but I cannot find anything for the 120, and they are different enough that I don't want to assume the 200 settings are appropriate.  Any guidance, or a link to the owner's manual, would be greatly appreciated.