I have a C&O 6-38406 Locomotive that takes off at full speed as soon as I apply track voltage. I am suspecting the main board($150.00) is at fault. I 'm also wondering if this is the FETS on this board that have failed. Any help will be appreciated .Thanks.
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That is not a FET problem. That is a signal problem. Put the engine on the track with the power off. Apply power to the track. If the engine starts (engine noise comes on) and it starts moving right away, then the engine is not seeing the command signal and is starting in conventional mode. Try running the engine in conventional mode. If that works, then you have signal problem. It could be a simple antenna wire is grounding out (touching the frame somewhere). I would make sure the antenna is not touching any ground. If that is not the case, it could be the radio portion on the board is dead. On some boards, it could be a bad solder connection for the radio. You would have to inspect the board to be sure.
@Joe Fermani posted:That is not a FET problem. That is a signal problem.
You assume facts not in evidence. This is an RCMC equipped engine, so it will not take off with no signal, it will start in neutral. The only way to get it to run away with loss of signal is two quick power interruptions.
In truth, this is more likely to be a real electrical issue.
My bad. I have mostly tmcc locs and assumed they behaved the same way.
A real electrical issue?
@amos posted:A real electrical issue?
Yes, a runaway meaning starts without command in a direction might indicate a pinched wire, blown FET or some other way that motor is seeing DC when it should not.
Opposed to a TMCC signal problem and the engine starting in conventional and then starting in forward when it should start in neutral.
Again, yes, you are not wrong to suspect a failure of the RCMC- specifically a failed motor drive FET shorted on "could" give the symptom you are having. Bigger question- what caused the failure and fixing that before the repair and just blowing it again or worse.
Do these boards or their FETS fail without a cause sometimes?The prospect of replacing the board(150.00) and having it fail again is concerning indeed. Thanks for any help.
@amos posted:Do these boards or their FETS fail without a cause sometimes?The prospect of replacing the board(150.00) and having it fail again is concerning indeed. Thanks for any help.
No, and that's what I'm getting at. You should know why it failed, solve that first -overcurrent or short to frame are 2 typical causes.
Pinched wires, motor failures, jammed mechanics stalling motors, high usage and loads, all just a few reasons that could root cause that.
I know I've put the shell on and have noise of something hitting and taxing the motors. I take the shell back off and re-route wiring so the hitting no longer occurs. When this does occur I don't just keep running it that way-I shut it down until I can take the shell back off. I guess it's possible it was damaged in this manner.Thanks,again. The information is greatly appreciated.
Truthfully, what kills them is something like a pinched wire or a dead short across the motor leads. Even a total motor stall will normally not damage the RCMC as it has motor stall sensing and protection. What can kill them is a dead short across the motor leads. I've had the crappy Canon motors in modern Legacy steam short out due to brush failure, that can and will take out the RCMC motor drivers.
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