Kicker KX600.4 repair

I was given a Kicker KX600.4 amplifier to see if I could repair it. The person said that when in the vehicle, the speakers would pulsate peak-peak even with no RCA's attached. Then they apparently bench tested it and it turned on then turned off and he described it as hearing crackling noises inside the amp.

So I take it home and hook it up on my bench and it powered on, no issues there, I plug 2 RCA's into the channel 1/2 and both channels work great, and same on 3/4 when RCA's hooked up on that side, however, i did notice that when the signal is being sent into 1/2, the same output is seen across all 4 channel's. I looked at the amp at least 10 times before I realized there was no switch that could cause the 1/2 input to allow the amp to amplify out of the 3/4 output, there just simply isn't that option like some other 4 channel amp such as my Alpines.

So im assuming I have a short somewhere causing channel 1/2 to get to channel 3/4. I cannot find any visually shorted components, so basically what im asking for is, does anyone have a schematic available for this amp, or any suggestions on what the issue may be just to get me started?
Well, I gave it a good go hooked up to a old subwoofer with a 4 ohm svc for 5 min, after that I turned off the signal generator and the sub was still humming at what seemed to be a frequency in the 60-100 hz range, but my meter did not pick up a solid frequency. Then I disconnected the sub and noticed it sucked back in which lead me to believe it was sending out a DC current, which it is, 6.12V on every output with no input signal input connected.

Perry, I still haven't run across this in your amp repair DVD, is there a section in the DVD that I should look in?

There isn't anything to address this specific problem.

Since it's on all 4 channels, it should be relatively easy to find.

Were you measuring the DC voltage directly across the speaker terminals?

Does it have DC on the outputs with no RCAs plugged in?

If you place the red lead on the positive speaker terminal and the black lead on the negative speaker terminal, is the polarity always the same (allways a positive voltage or always a negative voltage)? or do you get positive voltage on half of the speaker terminals and negative voltage on the other half of the speaker terminals.

Do you have both positive and negative 15v on the op-amps?

Email me a few photos of this amp so I can see what it looks like. Please zip them before sending them.
ok with no RCA's hooked up I get Ch1 = +5.88V, Ch2 = -5.88V, Ch3 = +5.88V, Ch4 = -5.88V

I checked what I believed to be the op amp, didn't have tonnes of time between class to look up a data sheet, but under the signal input board on the chip I found pin# 11 has 15 volts , but the 2 other chips in the PS section only had 10 volts, I forget which pins, I can look more in depth into that when I find time again this week.

I tried to attach a ZIP file of the pictures, but it wouldn't work, can I e-mail them to you?
Power up the amp and measure the DC voltage on the op-amps on the driver board. Pin 4 should have approximately -15v and pin 8 should have approximately +15v. All other pins should be near 0v.

Measure the DC voltage on each of the audio pins of the driver board RI, RO, RL, RR. Are all essentially at 0v?

Place the black meter lead on the secondary center tap for these measurements.

I received the email.
I am sending you an e-mail of an Excel spreadsheet I put together for the Op-Amps. The values are for sure off! Every single value was a positive voltage. I measured with the black lead of the dmm on ground and red did the probing.
The OpAmps were NJM4558L.

And on:
RI= 14v
You don't have any negative regulated supply voltage. Check the voltage on both the top and bottom boards. Sometimes the connectors have bad connections.

If you don't have it on the bottom board, go back to the regulator and check it there. The regulator transistors are the ones standing near the large green resistors (R61 and R64). I'm not sure which one is the negative. The transistor part number will begin and A or a B.

The first leg (emitter) will be the output to the op-amps. This leg should have approximately negative 15v on it.

The second leg (collector) will be the input from the power supply rail (via the green resistor). It should have approximately negative 40v on it.

The third leg (base) will go to the Zener diode. It should have approximately negative 15.7v on it.
The Zener is probably leaky. Pull one end of it and check it. With the meter set to diode check, you will read ~0.7 v in one direction and open in the other direction if the diode is good.

Do NOT power up the amp without the zener in the circuit. If you do, you're likely to destroy all of the op-amps in the amplifier.

If the diode is OK, pull one leg of R63 and check it.

If it's OK, the transistor is likely defective (low gain).
Thanks again Perry, thats 2 amps you helped me repair now. I am really glad I bought your repair DVD, it's not only worth every penny and then some, but to get the hands on support from you is almost priceless.

Very much appreciated!!
Im going to speak to my teacher and let him take a look over the DVD, I told him how helpful it is and how it would be a great addition to every students tool box, especially the 1st year students just learning about the particular electrical parts. If you receive an order of about 50 or so DVD's, then you know I did my job :)