Check for any high ESR or shorted caps. These do cause problems with
the output drive tansistors.

The switching supply transormer may be damaged if the switching
transistors were shorted. I have seen this before in other similiar
units.

Unless you are an authorized service rep for these products, I doubt
Yamaha will sell you the parts or service schematic. You may have to
send them the unit to have it serviced. If the unit is not a very
expensive one, it will pay to replace it.

Jerry G.
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