Is your Marantz Model 500 missing that little door?

Well,  maybe this will help you out. Here are the dimension so you can have one made. 

 

All measurements are taken in Millimeters

a) 13.2  b) 6.0  c) 15.5  d) 2.0  e) 2.1  f) 3.1  g) 3.0 

 h) 1.4  i) 0.5  J) 0.5  k) 0.5  l) 0.3  m) 1.2  n) 1.9

KENWOOD KX 630 Stereo Cassette Deck ( No sound output from Left channel)

I originally thought the unit probably needed a simple head cleaning, but I quickly found out, this was a more serious problem. Tracing the input signal, led me to the processor chips. one of them accepted an input signal and produced an output. The left one did not... BINGO!

 I found a bad LM1011 DOLBY NOISE REDUCTION PROCESSOR chips (seen in picture below)  This unit comes with two of them, a left & right. I replaced the left processor chip and the problem was solved! 

The LM1011 DOLBY NOISE REDUCTION PROCESSOR chip, is the same as the NTE 2003.

Sansui A 910 Integrated Amplifier (stuck in PROTECTION mode)

Stuck in protection mode. (The speaker relay does NOT click on) I checked voltages at the output transistors. The right side voltages looked good, but the left side voltages were bad ( that's why the relay doesn't click on)

I found a bad 45580 op-amp chips (seen in picture above)  location on the board (IC2) Replaced Chip and unit is working great now. Very nice sounding amplifier!

Pioneer QX 8000A QUADROPHONIC Receiver (no sound from Channel 2 & 3)

This is a four channel receiver, it had a problem with channels 2 & 3. Their was no sound output from either of these channel. The problem was on the control Amp Board. Capacitors C2 & C3 were found to be bad. Rate 0.47uf @ 25 volt.

Here's a Diagram of the bad capacitors

.