Trying to fix a broken car amp.

[David97]

Hi everyone. I bought a broken soundmagus Q-150 amp for cheap. The guy didn't say what was wrong with it but I assumed that it was something like bad transistors on the output line or a faulty PSU when I bought it. When I power it on it powers up fine, and does not go into protect mode. However when  speaker is connected it just ticks, like a clock. I have measured the voltage on the power supply while running and it measures a steady 32V, no sag when speakers are connected. I have also taken all of the output transistors out of circuit and they all behave as expected.


excuse the dodge cap. I did that because the original was swollen, and the electronics store didnt sell 3300uf, so I put in a 4700uf instead until the right ones arrive in the mail.

Because everything else is working fine, I think it has to be a issue with the preamps, or filters, something involved with the interpretation of the input signal. All the chips involved in this are getting the correct voltage. I'm not sure what to test next, but I have a feeling that it's going to get difficult without a oscilloscope.

I have a feeling that a way I could test this is by hooking up a pair of headphones to the RCA output on the amp. I think that this runs through all the filtering and preamp stuff, but not sure. Then If I got sound out of this I could verify that the preamps, and all that stuff is working correctly. I'm not sure about this, so if anyone knows that would be helpfull

Does anyone know what I should be looking at next? Or any advise on what It could be? Thanks, David.

[oPossum]

If all channels have that problem, then check the supply rails for the op-amps.

If it is just one channel, then check the SMD transistors that drive the outputs.

[Unelma]

Check all zener diodes.

[envisionelec]

Hi everyone. I bought a broken soundmagus Q-150 amp for cheap. The guy didn't say what was wrong with it but I assumed that it was something like bad transistors on the output line or a faulty PSU when I bought it. When I power it on it powers up fine, and does not go into protect mode. However when  speaker is connected it just ticks, like a clock. I have measured the voltage on the power supply while running and it measures a steady 32V, no sag when speakers are connected. I have also taken all of the output transistors out of circuit and they all behave as expected.


excuse the dodge cap. I did that because the original was swollen, and the electronics store didnt sell 3300uf, so I put in a 4700uf instead until the right ones arrive in the mail.

Because everything else is working fine, I think it has to be a issue with the preamps, or filters, something involved with the interpretation of the input signal. All the chips involved in this are getting the correct voltage. I'm not sure what to test next, but I have a feeling that it's going to get difficult without a oscilloscope.

I have a feeling that a way I could test this is by hooking up a pair of headphones to the RCA output on the amp. I think that this runs through all the filtering and preamp stuff, but not sure. Then If I got sound out of this I could verify that the preamps, and all that stuff is working correctly. I'm not sure about this, so if anyone knows that would be helpfull

Does anyone know what I should be looking at next? Or any advise on what It could be? Thanks, David.

The PT2313 is a CMOS Audio Switch. It's probably dead and won't pass a signal.