MTX Thunder 250X Protect

[kev79]

Ive been working on this dam amp for like a week now i cant seem to find why it will not run. here are my ic specs in protect mode.

Tl494 PWM

Pin 1: 6 mv
Pin 2: 4.49v
Pin 3: 67mv
Pin 4: 4.9
Pin 5: 1.7 sawtooth
Pin 6: 3.3v
Pin 7: GND
Pin 8: 13v
Pin 9: 8mv
Pin 10: 8mv
Pin 11: 13v
Pin 12: 13v
Pin 13: 5v
Pin 14: 5v
Pin 15: 5v
Pin 16: 8mv

Lm339


1. 0
2. 4.9v
3. 11.68v
4. 0
5. 3.12v
6. 4.2
7. 3.12v
8. 3.6v
9. 4.9v
10. 4.9v
11. 7.07v
12. 0v
13. 0v
14. 0 v

1,13,14 output pins all tie together.

So i checked all fets and recitfiers. all checked fine. so i hooked it up to my current limiting supply to limit about an amp at 13.8 volts and injected 5 volts dc from a point near the lm339 to pin 7 and the amp tuned on . So i hooked up my signal generator on the input rca's and a scope on my outputs and everything works fine , nothing is running away. ive tryed to hunt down why the amp is doing this but wihout a print i cant really tell. its a double sided well populated board and tracking traces on this is hard when it runs under other parts and to though holes in the board... so any suggestions what i can look for?

[kev79]

ok so i pulled the thermal resistors out and i found one to be 200 ohms at room temp and the other at 5k ohms so i pulled my bypass jumper off and the amp fires on ,, ive never seen one of these fail before. so wich one is bad is my next step to find out.

[kev79]

ok the 5k one is ok the 200 ohm one was bad