Slide a screwdriver under the chrome handle cover and snap it off, exposing the two bolts which hold the handle inn 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 its 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. Slide the chassis out of the case, depressing the reset button to clear the case as the chassis slides out.
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 furthest away from you. Remove the aluminum heat plate (about 6 x 20 inches in size) which is held in place with 8 screws. This will expose the two output boards. The main channel output board will be on your left and the monitor board on your right, nearest the speed control arm.
After determining which channel is malfunctioning unsolder the two wires which are connected to the little round thermal cut off. Remove the four screws which hold the board to the heat sink and then unplug the edge connector. Re-connect the edge connector to the new board before re-installing it on the heat sink. Put a drop of silicone cement or glue where the edge connector meets the board to keep it from working loose. Use clear silicone seal or equivalent; do not use any material which is a conductor. If you have further problems, call us.