What your seeing here is the chassis of an HO scale GE (General Electric) 45T switching locomotive sitting on my workbench for repair.
I purchased this small switching loco as a used unit with a known problem. The locomotive was very sluggish at slow speeds requiring the throttle to be advanced to a higher notch than my other DCC locomotives for similar speed on the track.
The on-board decoder provides variable DC power to the motor, with alternating current encoded with control information on the track itself that allows this DCC locomotive to operate with many programable features.
Although I operated it that way for some time, I still felt there was a problem that needing addressing, so I decided to dismantle it and see what I could find.
For power the locomotive has a double-ended 12 volt motor with double jointed universals driving brass pinions part of the gear-train within the trucks at either end of the chassis.
The gearbox's have bottom covers that I removed for closer inspection of the gear trains. Everything appeared in order, and I lubed all the gears before reassembling the gearbox's. I then moved to the universal joints and related pinions located at either end of the double-shafted motor.
I temporarily disconnected the universal joints from the motor, and then disconnected the two feed wires that connect the decoder to the motor. With the decoder bypassed, I proceeded to connect the motor directly to my variable DC power supply.
This proved that the motor turned freely without any strange noises or other problems like dry bearings on the shafts at either end.
Reassembly was in order, and with DC power to the motor being provided by the power supply, and the locomotive chassis elevated to keep the wheels from driving the locomotive, I powered it up.
At this point I realized that there was more sound coming from the one truck than the other. Knowing the gearboxes were not the problem. With closer inspection of the noisy truck, I discovered that one of the wires that connects the contacts to one side of the wheels and the decoder had not been routed correctly from the factory, and was wedged in between the truck frame and the universal joint mounted on one end of the motor. I rerouted the wire and the noise was gone, with the amp draw shown on the meter of my variable power supply dropping slightly indicating less load on the motor.
After testing the locomotive chassis on my HO layout indicating all was well. I blocked up the chassis with the locomotive under power for an hour allowing the drivetrain to break in before re-assembly and put back to work on my switching layout.
Expand the photo for a closer look.....
CN 1 back in service.....