The problem is not dirt if you can watch the rf signal on an oscilloscope and it drops off as the CD plays. It's the laser. Cleaning is rarely the issue.
I haven't given up on this, I've been really busy. I promise to get back to it. I have a Denon receiver with the same amp circuit in it and I can use that to check voltages and try different opamps and see how it affects a working circuit. I want to try different opamps in mine anyway to improve...
Also see if you can identify the reset line and look at it with a scope. Other things:
Look at the output of the IR receiver with a scope.
Tighten all screws on the pcb. They may be used to complete ground paths.
I will try to review the above later today. Do you have an oscilloscope? The rising current when you touch the base of that transistor indicates oscillation. Don't do it again for now.
Cadmium plating does have the gold tint with a rainbow finish. Most Japanese made audio equipment from the 1970's is cad plated. If you want to see if the plating is coming off, a standard test is to apply Scotch tape to it and pull it off. The plating should not flake off. If it does, that's bad.
You are going in a million directions at once, you need to be more methodical and look at one thing at a time. If you see a voltage that is grossly off, that is an area to concentrate on. voltages that are off by mV aren't likely to be a problem. D506 and D507 should have +/- 15V on them as...
We are babysitting our grand daughter tomorrow and I don't know if I will have time to check this, so I wanted to tell you you can use a 5532 as a temporary replacement for either opamp, but if you find that that is the problem, order a couple LM4562 opamps in 8 pin dip package. They are...
The diode below it is D527. Sorry, I was looking at it on my phone and had no way to open the schematic. Please test D527, TR551 and D509. On the schematic D509 looks like a LED..
That cap is for stability. It rolls the opamp off at some frequency so it doesn't oscillate. It is configured for unity gain. The feedback comes from R536 and R562.
Lots of information here to wade through. Are you sure you tested TR551? Please retest it using the Diode range on your meter with the power off. Also the diode right below it. I'll try to get back to this later.
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While I'm waiting for you to do the voltage checks, here is a primer on opamps:
1. An opamp is a device with a non inverting input and an inverting input.
2. If an opamp has no negative feedback around it, it will have extremely high gain. Theoretically it would have infinite gain but it's an...
So to start out, have a look at the block diagram below. From this you can see that the opamps are used in the DC Servo and feedback circuits and not in the bias. A2 and A3 appear to be feedback as well. To be continued...
I'll have a look at the schematic. I am not aware of Denon using an opamp in the biasing scheme. What I have seen is they use it as a voltage amp or feed forward. I have seen opamps used in a servo circuit to cancel DC. I bet that is what this is used for, and if so, a 5532 will work because...
I'm here every day, usually during lunch and dinner. I scan through the threads and chime in if one piques my interest or there haven't already been a whole bunch of good answers.