Well, the green light comes on, and the amp does not go into protect mode. There is no foul smell coming from it. I don't know what to check. When I connect a speaker to it, there is a trace of sound coming from it, but that is with the stereo cranked up. This is going to be the first amplifier I am going to attempt to repair myself since nobody around my area will do it. There is one dude, but I can't get in touch with him. I know nothing about how to start doing this. I have a DMM. I can get other stuff if I need it, unless it is overly expensive. I have a soldering iron. I can get a picture of the circuit board if that is necessary for anyone of you to help me.
A picture sure wouldn't hurt 🙂
Go for the easy stuff first 🙂 Root around in there and look for any physical damage with the amp off. Really spend some time - I've seen a simple easily visible error hours after I began probing all over a circuit looking for problems.
Since you know you can successfully power the amp do that. I would first check the power rail(s). A lot of car amps have metal bars that bring power from the power supply to the amp. Use the DMM to check the voltages there - it will tell you if you have a single or split HV supply for the amp. That may also give you a clue about the amp's topology.
Next I would measure the LV rails. Find an opamp and check pin 8 to pin 4 - It will probably be 24-30V [+/-12-15V].
Turn power off and check the output filter. The inductor should be virtually a short, cap should be virtually open. Check the zobel if it's there. Turn the amp on again.
I'd next go to the gates of the output FETs and see if you're getting a switching signal with no modulation - usually that's a 50% square wave going from ground to 10-15V or so. You'll need a scope at this point. Look at the gate signal referenced to the source.
I am assuming when you say it makes a trace of sound that if you put input in, you don't get anything out. The next step would be the trace the input signal [much easier with a sine or other repetitive waveform] through the opamp stages and see if it gets to the modulator. The modulator will probably be at the input of a comparator, but I have seen opamps used if the amp is LF only.
By that time you should have at least a basic clue of where the problem might be. That's just my suggestion off the top of my head and everyone else might do it differently. Hopefully some more people can shime in with suggestions as well. Good luck!
Go for the easy stuff first 🙂 Root around in there and look for any physical damage with the amp off. Really spend some time - I've seen a simple easily visible error hours after I began probing all over a circuit looking for problems.
Since you know you can successfully power the amp do that. I would first check the power rail(s). A lot of car amps have metal bars that bring power from the power supply to the amp. Use the DMM to check the voltages there - it will tell you if you have a single or split HV supply for the amp. That may also give you a clue about the amp's topology.
Next I would measure the LV rails. Find an opamp and check pin 8 to pin 4 - It will probably be 24-30V [+/-12-15V].
Turn power off and check the output filter. The inductor should be virtually a short, cap should be virtually open. Check the zobel if it's there. Turn the amp on again.
I'd next go to the gates of the output FETs and see if you're getting a switching signal with no modulation - usually that's a 50% square wave going from ground to 10-15V or so. You'll need a scope at this point. Look at the gate signal referenced to the source.
I am assuming when you say it makes a trace of sound that if you put input in, you don't get anything out. The next step would be the trace the input signal [much easier with a sine or other repetitive waveform] through the opamp stages and see if it gets to the modulator. The modulator will probably be at the input of a comparator, but I have seen opamps used if the amp is LF only.
By that time you should have at least a basic clue of where the problem might be. That's just my suggestion off the top of my head and everyone else might do it differently. Hopefully some more people can shime in with suggestions as well. Good luck!
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