I have an old school Rockford Fosgate Punch 75 with internal 15amp fuses.I am getting DC voltage out both channels I have checked all driver and output stage transisters with my trusty Simpson they seem to be fine.
I am thinking it is going to be a bad op am there are three in these old amps how do I know which one is the culpret.
I am thinking it is going to be a bad op am there are three in these old amps how do I know which one is the culpret.
Well I thought I would get some quick help on here . I will start by replacing the one clesest to a burnt 100 ohom resistor. It is most likely the culpret .
When I replace these op amps I always like to solder a socket in place of where the IC sits so I can easily replace it if I fry the new IC.
When I replace these op amps I always like to solder a socket in place of where the IC sits so I can easily replace it if I fry the new IC.
After Measuring the DCV on both channells
After measuring the DCV coming out of both chanells I found the voltage to be positive +-23 volts from the Orange wire to the black wire and a negative +-23 volts from the yellow to the Brown .
Keep in mind these amps use reverse wiring to bridge the amp.Between the two Hots or the bridge mode I found no voltage.Which means the negative voltage I measured was really a positive voltage. I hope I put that right.
After measuring the DCV coming out of both chanells I found the voltage to be positive +-23 volts from the Orange wire to the black wire and a negative +-23 volts from the yellow to the Brown .
Keep in mind these amps use reverse wiring to bridge the amp.Between the two Hots or the bridge mode I found no voltage.Which means the negative voltage I measured was really a positive voltage. I hope I put that right.
Those are the bridging wires, which are also the only wires you will have sound on or see a signal through the scope.
You either have shorted outputs or drivers.
Remove the corresponding fuses that go to the channels with the DC.
Does the DC go away with the fuses removed?
You either have shorted outputs or drivers.
Remove the corresponding fuses that go to the channels with the DC.
Does the DC go away with the fuses removed?
The op amp labeled NE5532P was shorted when I checked between pina 1 and 8 so I changed it out.No more DCV on the outputs but both channells are distorted.Do you think I may have another bad opamp
Check the D40D8 and D41D8 drivers to see if they are shorted.
Check the fuses with a multimeter, and check the fuse holders to make sure there is good contact between the fuses and receptacle and to the board.
You could have a bad op-amp but usually you will have no audio if that's the case.
If this amp is using fuses in the speaker harness check them as well.
Check the fuses with a multimeter, and check the fuse holders to make sure there is good contact between the fuses and receptacle and to the board.
You could have a bad op-amp but usually you will have no audio if that's the case.
If this amp is using fuses in the speaker harness check them as well.
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