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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If it has the BUZ transistors, confirm that none are leaking or shorted from the gate to the source. The BUZ transistors often short that way and many people miss the short the first time they check.
Yes they are the same as all the other channels.
The x21's all read 0.420 vdc
The x23's all read 0.650 vdc
The x21's all read 0.420 vdc
The x23's all read 0.650 vdc
With the bias fully clockwise, what is the DC voltage across the following resistors?
R452
R430
R431
R439
R452
R430
R431
R439
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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