I'll gi' a deek in the drooers away at the castle!
I may have something.
However, power is easy. Measure from the plus and minus power pins of the op-amps to the edge connector. There's usually 5.6Ω or 10Ω as a fusible resistor in line with the power rails... that'll tell you where the power goes.
There are 2 more sch.. but there 332k. I tried to shrink but it makes them unreadable. PM me and I'll email. They are Eq ,Insert and Power , mixamp, Buss driver