How to bypass MRC decoder in the Athearn Challenger?

[mmagliaro]

Fixing a first gen Athearn Challenger for someone... the one with the MRC decoder and
the remote control.  But... he had replaced the decoder with the Tsunami TCS-4664N drop-in
replacement for the MRC decoder.

I have no DCC set-up.  It won't run on DC because the analog isn't enabled.
But regardless, to test the quartering and rod repair I had to make, I really would
like to completely bypass the DCC electronics and run it on plain DC to test for mechanical
behavior, current draw, etc.

I am sure I could figure this out by popping the tender shell, pulling the decoder and figuring out
which wires go to the track and which go to the motor.  Is there an easier known way? 
(Maybe somebody out there knows that I could pull the decoder and just jumper a certain pair of pins
on the board to do this).

Thanks for whatever pointers you folks may have.

[mmyers]

Max,
 looking at the documentation for that decoder shows it has a 5 pin plug. Two pins will be track pick up, two for motor. One for headlight. I'd start wit a meter and find the two for track pick up first. My guess would be the outside  (1 and 5) pins. After finding the track pick ups, lokk for the light pin. just sit it on powered track and jumper the other pins. My guess on the light would be the center pin. That will leave the two motor pins. and you know what to do from there.

You definitely want to remove the decoder. Any voltage applied to the motor pins or light will blow the decoder.

Martin Myers

[mmagliaro]

Max,
 looking at the documentation for that decoder shows it has a 5 pin plug. Two pins will be track pick up, two for motor. One for headlight. I'd start wit a meter and find the two for track pick up first. My guess would be the outside  (1 and 5) pins. After finding the track pick ups, lokk for the light pin. just sit it on powered track and jumper the other pins. My guess on the light would be the center pin. That will leave the two motor pins. and you know what to do from there.

You definitely want to remove the decoder. Any voltage applied to the motor pins or light will blow the decoder.

Martin Myers

Thanks Martin.  Your approach is about what I expected.  I will have to disconnect the speaker as well, and I was planning to completely remove the board from the tender to avoid any chance of damaging the decoder.   Once I trace
the wiring, it won't be so bad.

[mmagliaro]

Just closing the loop on this.
The decoder board pops out with 2 screws and disconnects with connectors.  No desoldering needed.

And yep, jumper pins 1-2  and 4-5 on the 5-pin connector once you remove the board,
and that runs the DC track pickup straight to the motor.  Pin 3 is the headlight.
So I've got it running on straight DC now.  Runs great.