One or more of the power transistors are shorted. There are eight transistors in the amplifier section - 2 high & 2 low for each channel. This unit is difficult to open up to work on.
Unplug unit and check speakers with a multimeter to make sure they are not shorted.
Take off front panel (8 screws).
Remove power supply shield with yellow tape (2 screws).
Remove 2 screws holding top of power supply, loosen bottom screws.
Replace front and hold in place with a couple screws.
Turn unit around.
Remove screws holding heatsink (6 screws)
Open rear storage door.
Carefully pull amp section out, being careful of tightly routed wires. Note any connectors you disconnect.
The amplifier is the board on the top, the power supply is in the silver box.
Push the power supply forward and loose the black screws holding the amplifier board bracket closest to the heatsink.
Loosen the top brass screws holding bracket to heatsink and remove the bottom screws.
Remove all eight of the screws holding the transistor brackets & transistors to the heatsink. Look and take careful note of how the plastic insulators weave through the transistors. If you get this wrong, you can short out the whole amplifier when you turn it on.
Slide the amplifier board down and out where you can get to the bottom. Note the wires and connectors going to the small protect board over the amplifier.
Check the transistors with a multimeter to find the shorted ones. Remove and replace bad transistors. These are connected in pairs.
Reassemble in reverse. Be careful of reconnecting wires and insulators. Don't test until the amplifier PCB is back in place and you're sure of all wires. If the PCB is touching the power supply, you'll short it out.
Good luck, I told you this wouldn't be easy!
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