I got it to work Thanks. Ray
Hi, Ray
A decoder plugged in "backwards" should still work OK and not toast the decoder. NMRA did a good job of setting up the pins so this prevents harming the decoder.
I suggest you put the dummy plug back in the socket and be sure the Doodlebug runs OK on DC. If you have a meter that can reaad the current draw of the motor that would be helpful. Chances are though that the motor is OK and not drawing much over one amp.
With your meter you can set it to continuity (or some will beep when continuity is present) and set the doodlebug on a short length of track.
Place one probe on the right rail and with the other touch each pin socket. When you get a beep you found pin #8.
The pin across from it is pin #1 or the motor + (orange) wire.
https://dccwiki.com/NMRA_DCC_Plug
Does your board look like the one shown here?
https://estore.bachmanntrains.com/index.php?main_page=product_info&products_id=1047
If so you can see the pin numbers screen printed on it in the photo.
Sometimes you can follow the "traces" or copper film on the board and see which pin is soldered to the motor + or - or see where the right (red) or left (black) rail pickups trace back to the DCC plug.
This M-R review has a photo of the PC board with a decoder plugged in. It looks to me like the red wire is on the left side of the PC board therefore pin #1 would be on the left side toward the front of the board.
https://www.trains.com/mrr/news-reviews/reviews/staff-reviews/bachmann-ho-scale-motor-car/
Hope that helps, Ed
Does antone know which pin is #1 on the 8 pin conector for the decoder. It is not marcked on my loco and I have already fried a decoder. any help would be appreciated.
Ray