I am fixing this class D amplifier and i came across this component. Which is attached to the frame of the amp. Has anyone know what it is as other that this i cant find anything else that gone wrong. By the way this amp died at the momet the subwoofer box touched the seat to which the amp is attatched (wasnt rough hit) maybe this is some kind of protection that failed after a nudge?

 

My guess is thermistor, for reading the heatsink temperature for protection. When it bumped the seat, did anything short? Did you check the fuses? Did you check if the power supply side of the amp is making power? Also check the various transistors on the power supply side and the audio output side to see if any are open or short. Also check the output of the amp, and check the continuity of the speaker wires. Maybe the amp is still working but the bump knocked the speaker wires off inside the box?

 

I have checked allmoast everything apart from transistors which will probably be the case and the problem is in the power side of the circuit as the indicator led that tells if its short or open does not indicate anything so must be the power side i can also tell its power side by that the pin 12 on the PWM IC which is supposed to get 12V does not have anything. Thanks for information will check the transistors next.

 

Its marked TH01 which will be a thermistor & is unlikely to be faulty.

 

Is mains involved? If so, live could have been shorted to ground or something (worst case scenario). Or sometimes - has continuity with earth, so if + touches another earthed appliance, it shorts it out. Was there any "magic smoke"? And check your caps. They may have been operating too close to the max voltage and quit their job. Finally, do some quick continuity tests. It could have scratched a thin PCB trace or caused other damage too it. Also, a picture of the whole thing would be nice, a schematic would be great if you can find it.

 

There the whole thing, unfortunately no schematics, it is a car audio amp Boshman zx3-s4e, nothing poped no smoke came out of it and there is no burnt component smell or anything the wiring was good. Done a lot of continuity tests everything seems to be fine with the pcb. I have also replaced the pwm module as i suspected this to be gone wrong as other components seemed to be fine but no help.

 

Is the power supply oscillating at all?

 

If you suspect a mechanical knock caused the problem, try looking with a good magnifier for a dry joint or hair-line crack in a pcb trace close to any heavy/large component such as a connector, big cap or transformer.

 

My guess is thermistor, for reading the heatsink temperature for protection. When it bumped the seat, did anything short? Did you check the fuses? Did you check if the power supply side of the amp is making power? Also check the various transistors on the power supply side and the audio output side to see if any are open or short. Also check the output of the amp, and check the continuity of the speaker wires. Maybe the amp is still working but the bump knocked the speaker wires off inside the box?

That device is certainly a bead type thermister epoxied into a wire lug. That is a common way of enabling them to be thermally connected to a heat sink.
And for the failure concurrent with the bump, I have seen fragile speaker voice coil connections come apart, and I have seen poor solder connections fail with just a gentle tap. I have been in the situation where it was much faster to simply re-heat all the solder connections on a circuit board rather than try to locate the failed one. Of course, it takes a good hand, a good magnifier, and a hot iron with a sharp tip.