Wiring help needed for Lionel GP-20

[Neil Robinson]

My lack of familiarity with these models means I'm incapable of performing what should be a very simple fix.

 

An internet search didn't find a useful circuit diagram.

 

The loco in question is a Burlington Northern example catalogue number 8-850003.

 

One minute it was running fine, the next it came to a dead stand with nothing functioning.

 

Removing the body revealed a detached wire,  A in the photo. I can't find any clue to where it should be attached. The other end of it is soldered to a pad, marked B on the photo on the underside of the board. On the wire side it is marked + on the board, this reinforces my suspicion that it's important and may be the only problem. The adjacent four wires are marked T, C, and two SW. All four of these connect via twist on connectors to the rest of the wiring. I was expecting to find the remains of a bit of surplus wire in one of the other twist on connectors, but no luck.

 

As it's not my loco I'm particularly keen on not finding out the hard way of where not to connect it!

 

[enginear joe]

 I'd love to help but honestly never seen the inside of one of these. Before I hazard an incorrect guess, I bet Chuck here on this forum could help you out when he sees this. I can only guess he's busy. I'm pretty sure he'd know. Maybe not though. Does this have the railsounds board inside?

[Chuck]

There's wiring diagrams for the Lionel GP9 online...somewhere 

 

I sold all mine because of the crappy way they pick power from the rails. I'd first check continuity from the wheels to the circuit board...chance are the brushes on the backside of the wheels are dirty and not making contact. Aluminum wheels don't help at all.