Rockford Fosgate Punch 360a2

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Hello everyone.

I have a Punch 360a2 board number PC-2036-C

The power supply and both channels were defective.

I repaired the power supply and all is well.
I repaired the right channel and all is well with that as well.

The left chanel is still defective. I replaced all the outputs, the gate resistors, the source resistors, and a few smd transistors and diodes that were burned.

The left channel has no DC present but it will not bias and only produces the top half of the waveform.

Any ideas where to look next?
 
Double-check the 0.1 ohm resistors. If they're well out of tolerance, the amp will clip the output when driving a load.

If those are OK, double-check the transistors in that part of the protection circuit to confirm that there are no bad solder connections, no bridges and all of the transistors are the right ones for each location.
 
OK getting back to this amp after catching up on lots of repairs and bringing it back to the top. Lifting D104 allows the left channel to bias and produce the upper and lower half of the waveform. It also produces clean output on the scope and with a load to a speaker.

As I already stated I replaced every smd transistor and diode in the channel due to several being burnt. I have verified they are all in the correct spot. All of the 0.1 ohm source resistors are new and within tolerance. I have checked alot of the smd resistors and they seem OK.

Any ideas where to go next?
 
Solder the resistor back into the circuit and start desoldering the next transistors in line going towards the 0.1 ohm source resistors. Do this one at a time, reinstalling the one that has previously been removed. At what point does the amp no longer produce clean audio?

So re-install D104 diode ? The amp will immediately produce distorted sound with this diode installed. Maybe I didnt understand your request??
 
I decided to remove R153-R159 from the circuit to accurately test them.

I found R155 to be way out of tolerance, I replaced it with a new 1K resistor and the amp plays clean sound with a load and produces and clean sine wave.

Thanks for all you help Perry, when you told me to short the base and emitter of Q117 I did and referred to the schematic and it was obvious what I needed to check.

Thanks to you as well brandes.cm
 
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