Hello all, I am fixing a punch 4040 dsm amplifier I got for free that had a shorted output transistor that caused the left rear channel to output rail DC. I have replaced all the buz11 output transistors and it solved the DC problem, but now the audio in that channel is scratchy and distorted at all volume levels. I've tried playing with the gain, treble, bass, phase, and input switches to see if any of those were causing it (like if they need a touch of deoxit for example), but no go.
What causes this and what parts would I need to replace next?
What causes this and what parts would I need to replace next?
To troubleshoot the scratchy audio problem, I took a source resistor off another channel and put it on the left rear channel and the channel I took the resistor off of now has the scratchy audio. Gotta order some .1 ohm resistors now.
The DC problem in the left rear channel resurfaced again, unfortunately. I had the amp go into protect at one point.
The DC problem in the left rear channel resurfaced again, unfortunately. I had the amp go into protect at one point.
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Yessir, it does now.
I found out why I think that DC issue happened: I had a voltmeter hooked up to the bad channel and wiggled the driver board for the channel and the DC went away, indicating a broken connection. To fix that, I reflowed and added new solder to the board's connections, and that fixed it. That issue might have also blown the source resistors and transistors for that channel as well (correct me if I'm wrong).
I now have to order some 0.1 ohm resistors and all the channels will be sounding good. Thanks a lot for your help, Perry.
I found out why I think that DC issue happened: I had a voltmeter hooked up to the bad channel and wiggled the driver board for the channel and the DC went away, indicating a broken connection. To fix that, I reflowed and added new solder to the board's connections, and that fixed it. That issue might have also blown the source resistors and transistors for that channel as well (correct me if I'm wrong).
I now have to order some 0.1 ohm resistors and all the channels will be sounding good. Thanks a lot for your help, Perry.
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Metal film or metal oxide film.
I think these were used in some amps.
https://datasheet.octopart.com/MOS3C221J-KOA-datasheet-13176473.pdf
In amps where there are parallel outputs in a channel, I recommend 1% parts in Rockford amps but this amp has no parallel outputs.
I think these were used in some amps.
https://datasheet.octopart.com/MOS3C221J-KOA-datasheet-13176473.pdf
In amps where there are parallel outputs in a channel, I recommend 1% parts in Rockford amps but this amp has no parallel outputs.
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