Harmon Kardon FL 8450 CD player display is dark and disk motor spins continuously

When powered on the display is dark and disk motor spins continuously. Possible Power supply problem.

Checked positive and negative 12 volt regulators, both check good.

Checked positive and negative 5 volt regulators, the negative was good but the positive 5 volt was outputting  zero volts. So I checked the input to the regulator. It was suppose to be 13 volt but it was sitting at 1.2 volts. So it's not the regulator, it the input to the regulator.

 I traced the input leg back, and I found a bad 1 ohm resister. (R312) was open. Replaced resistor and problem was fixed.

Mitsubishi M R8010 Receiver, Left channel has no output sound

When an amplifier or receiver has an output problem. (no sound from either of the channels) It's usually bad output transistors in the amplifier section. But before you just assumed that, you need to make sure the problem is not in the preamp section of the unit. Lucky for me this particular receiver had the jumpers between the preamp and Amplifier, so it was easy to check the two sections.

Output of the preamp section was good on both channels. So this means the problem is in the amplifier section. Possible output transistors. All output transistors and the surround sound power module was good. This particular unit had an STK3122II Audio Power amplifier IC that feeds the left and right output transistors.

I removed and tested it. I found that the left side was defective. Replaced it and problem was solved.