Atlas/Roco EMD GP9 - Repair Help

I went back and tried some more!

I now see that uncoiling the wires in the box with the one big screw allows one to move the motor and the trucks a bit.

There is a pin that holds the truck in the frame, but the wires make it hard to drop the truck, even with the pin removed. Are these attached with a slip connection? It looks like a very difficult place to solder. Even reattaching a slip connector might be a problem.

The motor moved enough to allow me to remove the 'universal joints' that drive the trucks. I managed to get at the commutator with some 'Conductalube' and a small cloth. The cloth came away very dirty. When I attached the motor to the tracks with clip leads, it spun up fine.

Perhaps I can get this one running.

Baumgrenze

Here's another pointer. The pin for the pinion gear at the top of the truck drive train, which also secures the truck in the frame, is ~0.060" which is only slightly smaller than a #17 brad. If you remove the head from a brad, chuck it in a drill press, and then gently dress it with a file and then some fine emery paper, you can make a ~0.18" long 'keeper pin' which you can insert as you withdraw the factory pin. When you reassemble, you reverse the process and push the keeper out. With the keeper in place you can drop the truck without displacing the pinion gear.

I took the first truck apart completely. It did not seem all that filthy and it was a PITA to reassemble, especially getting the pinion gear aligned. I also had to resolder one wiper.

I think I will just 'slosh' the second with rubbing alcohol, let it dry, and lube it. I'll put a droplet of the 'Conductalube' on the wipers in the hopes that they will stay clean a bit longer.

I've been cleaning the conducting wheel surfaces with a bit of 0.5 micron lapping tape that a neighbor brought home from the flea market. I wrap it around a flat toothpick and wet it with rubbing alcohol, or, if the tarnish is stubborn, with Deoxit or Conductalube. It leaves a nice clean, smooth wheel surface.

I thought I'd document what I've learned, both for comments and for future use by others, perhaps.

Baumgrenze

Harbor Freight sells a small sonic cleaner (used for jewelry) on sale occasionally for low cost. If filled with the _correct_ solvent the whole or parts of the engine could be put in and cleaned. Then just relube. Here the _correct_ solvent is the trick, make sure it will not hurt any parts of the engine.

Jon Miller spake thus:

There's nothing to worry about so long as you don't use extremely strong solvents like acetone (lacquer thinner) or MEK. Myself, I'd use lighter fluid (naphtha), which dissolves oil and grease like a charm and won't harm plastic (not even styrene). Better than alcohol.

So sulfuric acid's right out is what you're saying...