Rockford Fosgate Punch 200IX
 

Can anyone tell me the value of R157 and R257? They are very burnt and I can't read the color codes.

220 ohms.

I emailed you the schematic diagram.

Thanks Perry got it.

Ok stay with me this amp seems to be a basket case.

Rebuilt power supply and all is well with that.

4 new IRF3205's, 4 new 47ohm gates, 4 new driver transistors. Amp powers up fine and idles.

L&R channels have recieved all new output fets, all new gate drives, and all new emitter resistors.

R157 and R257 have been replaced.

LM339 reads as follows:

pin 1: 4.41 vdc
pin 2: 4.41 vdc
pin 3: 17.87 vdc
pin 4: 0.188 vdc
pin 5: 2.995 vdc
pin 6: 4.34 vdc
pin 7: 4.99 vdc
pin 8: 4.67 vdc
pin 9: 2.916 vdc
pin10: 4.99 vdc
pin11: 8.21 vdc
pin12: 0.002 vdc
pin13: 4.39 vdc
pin14: 0.080 vdc

Amp produces 75.5vdc rail voltage and all op-amps have -16/+16 vdc on supply pins.

L+ bridging terminal has 16.5 vdc

R- bridging terminal has -2 vdc and bleeds down fast

The left channel wont bias and is very distorted, and the right channel has audio but tries to bias as soon as you try and turn the pot at all.

Q242, Q244, Q245 all have no rail voltage and have +37 vdc on their drains.

243, Q246, Q247 have rail voltage and have -1.950 vdc on their drains and bleeding down fast.

Q143, Q146, Q147 have rail voltage and all have +15 vdc on their drains.

Q142, Q144, Q145 have 1/2 rail voltage and all have +37 vdc on their drains.

I know this is alot of info but thought someone could kick it around looking at a schematic and maybe point me in the right direction to start.

Let's start with the 200-series channel.

Are you saying that the source legs of Q243 has no rail voltage?

Q242, Q244, Q245 source legs have no rail voltage.

Q243, Q246, Q247 source legs have rail voltage.

I goofed up in my typing in the original post these new readings are correct.

What's the DC voltage across R266?

-0.176 vdc across R266

Post the voltage on all three terminals of the following transistors. Place the black meter probe on one of the non-bridging speaker terminals. Place the red meter probe on the point where you need to measure the voltage.

Q128
B:
C:
E:

Q129
B:
C:
E:

Q118
B:
C:
E:

Q119
B:
C:
E: