Slide a screwdriver under the chrome handle cover and snap it off, exposing the two bolts which hold the handle in place. Remove these bolts. On the opposite side of the unit, locate the two rubber feet. Remove the bolts that hold these feet in place.
Make sure the tone arm is locked in it's clip. Lift out the platter, and set it aside. Be careful, not to lose the little ball bearing on which the spindle turns. Put a piece of tape over the hole so that you don't lose the ball bearing when you later turn the unit upside down. Pull the cord out of the cord holder space, and stand the unit up on the end where the rubber feet were. You can now slip the chassis out of the case.
Turn the unit bottom side up on a soft pad and orient it so that the front panel is nearest you and the speaker jacks are farthest away from you. Remove the aluminum heat plate (about 6 x 11-1/2 inches in size) which is held in place with 6 screws. This will expose the two output boards. The main channel output board will be on your left, nearest the transformer, and the monitor board on your right, nearest the speed control arm.
After determining which channel is malfunctioning, make a careful sketch of the wires leading to the output board. Before unsoldering the wires make sure your sketch shows which colored wire goes to which post. Unsolder these wires and remove the four nuts holding the board in place. Install the new board, resolder the connections, and reverse the above procedure to put the chassis back in the case. If you have further problems, call us.