Yet another 2270 bias question

[ZombyWoof]

part one:
I have recently recapped a 2270 and replaced output transistors, one was shorted. This is a serial number 46308J4 with a P750 that is a little different from the schematic. It has four pots on the board. The two in the center of the schematic, R794 and 795 have no technical description in my manual. Looking at the schematic these would appear to adjust the bias on the driver stages. Anyone have a clue as to the proper adjustment procedure for these? The drivers run considerably warmer than the outputs but clipping power is about 63 watts rms at 8 ohms.

part two: I love the amp and it makes sweet noise but they should castrate the goof that engineered the 2270. Too many changes, too many undocumented changes, too many unknowns

 

[catrafter]

There are at least two different versions of the 2270.
The adjustments in the basic service manual are for serial numbers below 3901.
The way to work on this stuff when the manuals haven't been updated is to deduce what the intent of the adjustment is and see how that can be applied to the current version of the circuit. It would be nice if everything was cook-book, but that's not the reality of it.
In section 15 step 6.5, where it says adjust R783 and 784, you would adjust R794 and 795. I will leave it up to you to sus out the J numbers for the alignment. Try not to blow up your amp while you are doing this, it is a distinct possibility.

For serial # 3900 and greater, to set the bias:
Connect your meter, set to DC millivolts to J754 and J760. Adjust R763 for 10 millivolts.
If you want to find out why your drivers get warm and your outputs stay cool, read ecluser's excellent analysis for everything you might want to know about the subject of bias and temperature compensation.

Tom

 

[ZombyWoof]

Thanks for the experienced insight.