I have a Punch 200.4 board number PC-3084-A
I am having troubles tracking down some distortion.
I recieved the amp and the power supply was toast and one channel had a shorted output fet. It used the BUZ 272 and BUZ 21 outputs.
I switched them out for IRF540 and IRF9540.
The DC on the bridging terminal went away and the amp powers up fine and idles fine and does not draw current. The 3 and 4 series channels were the ones repaired. The 4 series channel has the problem.
The 3 series channel will bias and puts out clean audio, but the 4 series channel will not bias and it is badly distorted.
Any ideas where to look?
I am having troubles tracking down some distortion.
I recieved the amp and the power supply was toast and one channel had a shorted output fet. It used the BUZ 272 and BUZ 21 outputs.
I switched them out for IRF540 and IRF9540.
The DC on the bridging terminal went away and the amp powers up fine and idles fine and does not draw current. The 3 and 4 series channels were the ones repaired. The 4 series channel has the problem.
The 3 series channel will bias and puts out clean audio, but the 4 series channel will not bias and it is badly distorted.
Any ideas where to look?
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When trying to test the voltage across R452 the amp drew massive pulsing current with the bias fully clockwise.
This tells me there is a connection issue with that resistor to the board.
Upon removing it I found a broken traces, actually a few broken traces.
The trace from the source leg of Q411 which then goes to R448 from there connects to R452. The trace is broken in between R448 and R452.
I also found a broken trace that leads to R432 either from R430 or R461, not sure without removing them as I do not have a schematic.
This could be obviously causing the problem?
This tells me there is a connection issue with that resistor to the board.
Upon removing it I found a broken traces, actually a few broken traces.
The trace from the source leg of Q411 which then goes to R448 from there connects to R452. The trace is broken in between R448 and R452.
I also found a broken trace that leads to R432 either from R430 or R461, not sure without removing them as I do not have a schematic.
This could be obviously causing the problem?
I repaired the traces and the channel bias works fine and it produces clean audio.
Surprisingly the 3 series channel is now doing the same thing as the 4 series channel was. I dont know what changed, but it wont bias and it has distorted output. I have checked everything up to the point where you asked me to turn the bias fully clockwise and check the voltage across R452, R430, R431, and R439.
Should I do this for the 3 series channel?
Surprisingly the 3 series channel is now doing the same thing as the 4 series channel was. I dont know what changed, but it wont bias and it has distorted output. I have checked everything up to the point where you asked me to turn the bias fully clockwise and check the voltage across R452, R430, R431, and R439.
Should I do this for the 3 series channel?
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