My Precor M9.23 treadmill stopped working, and after reading the troubleshooting manual and looking at the motor control board, the led indicated that the board is bad. Upon removal of the board, I saw that one of the diodes had failed (blown open). I can't see any indications on the diode to know what to replace it with, but attached is a close-up image of the blown diode, a similar circuit board with the diode intact, and a close-up showing the intact diode in question (small black/gray cylindrical, I believe uni-directional).
2 questions, should I attempt to replace the failed diode, or is it's failure likely the result of some other failed component? I'd rather not replace the entire board if possible, it's ~$300 US.
What can I replace it with? I can't make out what the markings mean. It's roughly 10 mm in length.
I've tried looking for the circuit diagram for this board, or better pictures of the TVS diode, but no luck.
Thanks.
Best Answer
This failure is the tip of the iceberg. TVS stands for transient voltage suppressor. It's job was probably to clip unusually high voltages to keep the rest of the circuitry safe.
If the above is true, then sufficiently high voltage at sufficiently long duration and low impedance came along to blow out the TVS. This means it no longer served its protective function, so the high voltage most likely proceeded to blow out other components. Very likely, there are several dead components now on that board.
Basically, that board is toast. Unless you have a schematic or a service manual, there is little you can do about it except replace it.
However, before replacing the blown board with a new one, try to figure out what killed the first board. Did you have a nearby lightning strike? Is the unit intended for 120 V and was somehow plugged into 240 V? If you don't identify the problem, you can't know the new board won't be subjected to the same over voltage, and fry as soon as you install it.