Did I screw up my locomotive motor?


oplholik

oplholik

Member
Saturday I bought a DCC system and a decoder for my Athern SD75M N scale loco. I first set up the Digitrax Zephr to run the loco DC, and it ran good. Then I took the shell off and pulled the DC decoder off in prep for installing the DCC decoder. To make this a little shorter, without installing the DCC decoder I reinstalled the DC, put the shell back on, set the loco on the track and tried to run it, it wouldn't move. The control is still set for dc. Then I noticed that there was one of the large pins that I use to hold track down laying across both tracks, how it got there is beyond me, but I'm wondering if that would have done something to the motor. The lights on the decoder still light up, but that's it. I can't see what else it might be. Thanks.

Paul
 
Most boards have a plug that has to be installed to have the engine run on DC. If the plug is out, the engine won't run because the motor is waiting to see a DCC signal. Did you happen to remove the plug when you were getting ready to install DCC and not replace it when you went back to DC?
 
Kinda my thinkin', too, Jim. I've done that more than once in my early DCC days.

Many times I've left the jumper on the bench only to find it when I came back to "fix" the engine.

Bob
 
UP2CSX said:
Most boards have a plug that has to be installed to have the engine run on DC. If the plug is out, the engine won't run because the motor is waiting to see a DCC signal. Did you happen to remove the plug when you were getting ready to install DCC and not replace it when you went back to DC?
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I didn't see anything like a plug, however I'll take another good look at it. There are two contacts that touch the frame from the motor, maybe one of them slipped or something. Thanks.

Paul
 
Paul, it's usually just a piece of black plastic with pins that goes into the eight or nine pin plug that you use to connect a DCC decoder to the existing lighting board. It's easy to remove it when you're putting in a decoder and forget it was there if you don't put in the decoder. If the locomotive is really DCC ready, there should be no contacts that touch the frame from the motor.
 
UP2CSX said:
Most boards have a plug that has to be installed to have the engine run on DC. If the plug is out, the engine won't run because the motor is waiting to see a DCC signal. Did you happen to remove the plug when you were getting ready to install DCC and not replace it when you went back to DC?
Click to expand...

stationmaster said:
Kinda my thinkin', too, Jim. I've done that more than once in my early DCC days.

Many times I've left the jumper on the bench only to find it when I came back to "fix" the engine.

Bob
Click to expand...

oplholik said:
I didn't see anything like a plug, however I'll take another good look at it. There are two contacts that touch the frame from the motor, maybe one of them slipped or something. Thanks.

Paul
Click to expand...

UP2CSX said:
Paul, it's usually just a piece of black plastic with pins that goes into the eight or nine pin plug that you use to connect a DCC decoder to the existing lighting board. It's easy to remove it when you're putting in a decoder and forget it was there if you don't put in the decoder. If the locomotive is really DCC ready, there should be no contacts that touch the frame from the motor.
Click to expand...
N scale diesels don't have jumper plugs.
I put a Digitrax decoder in my Athearn SD70M, and it works well, but you need to carefully isolate the motor. The light board that comes in the SD70/75 is not a decoder, all it does is connect the frame halves to the motor, and is a spot for the manufacturer to mount the headlights. It's likely the contacts for the motor are not touching the circuit board, or the circuit board is not getting a good connection from the frame.
 
Last edited by a moderator:
bnsf971 said:
N scale diesels don't have jumper plugs.
I put a Digitrax decoder in my Athearn SD70M, and it works well, but you need to carefully isolate the motor. The light board that comes in the SD70/75 is not a decoder, all it does is connect the frame halves to the motor, and is a spot for the manufacturer to mount the headlights. It's likely the contacts for the motor are not touching the circuit board, or the circuit board is not getting a good connection from the frame.
Click to expand...

Your SD70 should be the same set up as mine. When you installed the decoder, did you have to trim the downward tabs to keep them from touching the motor can? How is the best way, a small pair of snips? How about bending the elect. wires to touch the tabs on the board? And finally, were you able to do this by just loosening the frame screws or did you have to completly split the frame? Although I don't want to try installing the DCC board until I can get it to run on DC again. And so far that ain't happening. I just realized that the first time I ran it on DC, the controller hummed, which the instructions said was normal when running a DC motor, now I don't even get that. Thanks for your help, and I apologize if this is getting too long winded here.

Paul
 
I bent the tabs on the motor leads out slightly, and soldered them to the ears on the decoder. I then put a slice of the yellow kaptan tape between the ears and the metal frame.
 
bnsf971 said:
I bent the tabs on the motor leads out slightly, and soldered them to the ears on the decoder. I then put a slice of the yellow kaptan tape between the ears and the metal frame.
Click to expand...

I don't know what this tape is. Is this the tape that came wrapped around the DCC board that held it to the styrofoam?

Paul
 
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