So I have an MRC #1812 Sound Decoder in my N scale GP15-1. Whenever I place the engine on the track, it takes off without being commanded to do so. I can sound the horn, and other various sounds, but I cannot slow it down, stop it, or speed it up. I've searched and have never heard this problem before with any decoders? Anyone know how to stop this from happening?
gatrhumpyAnyone know how to stop this from happening?
Jim,
Do you own a pistol?...
Tom
https://tstage9.wixsite.com/nyc-modeling
Time...It marches on...without ever turning around to see if anyone is even keeping in step.
Sounds like a frame to motor short. Did you install the tape like the decoders instructions said?
Yep. I have had this decoder for a year and it was working fine. I doubt it's that because there is no way tape would come off, or anything like that. Why would a ground suddenly appear on an engine that was working fine for the past year?
gatrhumpy Yep. I have had this decoder for a year and it was working fine. I doubt it's that because there is no way tape would come off, or anything like that. Why would a ground suddenly appear on an engine that was working fine for the past year?
Had the loco experienced any recent derailments?
Whenever I have had a loco that was running fine, and suddenly decoder problems develop, it has been after a derailment when, for whatever reason, a short has occurred.
It could be a short.
Have you tried resetting the decoder to factory default mode?
Rich
Alton Junction
Never derailed.
Just tried to reset CV 8 to 8, and I can't put it on the program track because a short circuit was detected. Grrrrrrr.
Took it apart, and the only thing I could think is that the two prongs from the motor are touching the frame somehow, but they're connected to two pads on the bottom of the decoder.
The heck?!
There's your problem. The motor has to be isolated from the frame. Isolate the prongs and the problem should go away. Hopefully the decoder isn't fried. Joe
It doesn't take much to short the loco on a DCC layout.
You need to isolate those prongs with a piece of Kapton tape.
Once you do that, you need to test the decoder to see if it is fried.
Keep us posted.
This is what's pissing me off. I used a multimeter, and the prongs ARE isolated.
Why would the decoder still function if the motor leads were connected to track power?
The thing is a runaway locomotive. It's at full speed. I cannot slow it down. I tried to set CV8 to 8 and it does not respond.
I checked the resistance between each side of the frames. Nothing.
I checked the resistance between frame and same side motor lead. Nothing.
What the heck!
I placed the frame on the track for a split second and the rear light flashed VERY fast, like a short is present. I know it's present but I cannot find it.
Try disconnecting the decoder from the locomotive and run it on DC to see if the short still exists. If the problem goes away then you may want to inspect the decoder board to see if some solder has bridged a pad.
Dont' have the original decoder board to do that.
Engine running wild......typical MRC decoder failure.It wouldn't be the first one to do this.
The MRC decoder that came in my N scale challenger did the same thing. File thirteen it.
At this point, it is beginning to sound like the problem is the MRC decoder.
Probably the best advice is to pick up an NCE decoder or a Digitrax decoder and be done with it.
But before you install another decoder, make sure that the motor and brushes are isolated from the frame.
Otherwise, the decoder will be instantly fried.