Update: Wiring loco lighting guidance sought

[mecgp7]

I removed a decoder from an IMRC FP unit and replaced it with a DC board supplied by my good friend Jon (he's bailed me out a million times)! The DC board did not have a headlight wired so I attempted to solder the wires and headlight from another IMRC unit. The loco ran fine before wiring the headlight. I soldered the wires to the same two places on others IMRC boards. Once soldered and checked for any possible shorts, I attempted to run it. Dead as dead can be. There just happened to be another loco on the track and it ran just fine which leads me to believe I didn't short anything out. I detached one wire removing all possibility of  a short and still nothing. It wasn't until I remove the other wire that the loco ran. There wasn't any stray solder between the points on the board where the wires were attached.
So, what did I do wrong?

[MK]

Can you post some pictures showing what you did?

[mecgp7]

Can you post some pictures showing what you did?

Unfortunately, I pulled it all apart. I replicated other IMRC light boards even using the wiring and light from another unit. It's just weird that it wouldn't run with only one wire connected because you would think that I had a short on the board. But it wouldn't run until both wires were removed which means it wasn't the board.

[peteski]

Unfortunately, I pulled it all apart. I replicated other IMRC light boards even using the wiring and light from another unit. It's just weird that it wouldn't run with only one wire connected because you would think that I had a short on the board. But it wouldn't run until both wires were removed which means it wasn't the board.

With the description you provided (about the circuit) there isn't enough info to make a guess as to what the problem was.

[mecgp7]

Well since I failed at adding wires to the light board on my IMRC F units, I looked for an alternative. I took a Kato F unit light board which normally has the light bulb sitting over or on top of the circuit board. I bent it out so that it was pointed away from the board. I test fit it in the chassis upside down because the circuit on the board didn't allow for it to lay flat. There were two holes in the board already so I drilled through each into the chassis and screwed it into place. No need to tap the holes as the chassis metal is soft. I had to add insulating tape under the board where the circuit wires go through to the other side of the board. The board is directional and provides just the right amount of light. Not much good for you DCC guys, but it works for me.
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