you can pull both sp-40's, then connect pins 2 4 and 6 together.
This will eliminate the modules, yet allow the amplifier feedback circuit (the 2sa798 and 2sc1438) to dc balance itself and allow the protection to operate, then watch and wait for the protection to pop out. You CANNOT have ANY load on the outputs, no headphones or speakers.
If it is stable, and behaves, you know it's the modules.
When the protection misbehaves, then look at Q5, q6 2sc1649, the 0.22uf caps if still original, and then the rest of the protect circuit.
