I have a LL SW1200 (CN 1300) that I had converted to DCC. It ran well before on straight DC, but when it was returned to me it stalls, only starts to operate at speed step 60+ forward and basically not at all in reverse unless pushed (and then only at SS120+). At lower speeds it hums but seems to bind. I've disassembled the shell, the trucks are not binding in of themselves. I placed the frame on the tracks and got the above results. Whats the consenses? Is it a decoder or a motor issue. Do any fixes come to mind?
I doubt it's a motor issue. It's more like an installation problem. Three guesses: (1) The motor cradle might have been crimped during the disassembly/grinding/reassembly process. (2) One of the plastic pillows was reinstalled incorrectly--they look square, but only go in one way. (3) A wire is rubbing against the motor core. Since this is happening with the shell off, two possible fixes comes to mind. (1) Loosen the screws that hold the split frame together maybe one-eighth turn. The little spacers are compressible. If that doesn't work, (2) Take the frame apart and check to see the pillow blocks are installed the correct way. There are two little marks on opposite sides. The blocks have to go into the holders a certain way--and I'm sorry, I've forgotten which way, whether you can see the marks or not see them. Actually, a third thing just came to mind. Make sure there's enough clearance around the brushes, where the decoder is wired to them. I've had to grind out a little space. Otherwise, the brushes can be pushed against the armature too tightly, another source of binding.
