Teletype Troubleshooting

I am looking for troubleshooting tips for a 33 teletype. I'm testing in local mode and am getting incorrect characters on (almost) every keypress. The characters will change even with repeated pressings of the same key. I am pretty sure the keyboard is outputting the correct codes. I wiped down the distributor surface (it was pretty grimy) and no change. I tried adjusting the range finder but could never find a point where the characters were consistent. Is it possible to disconnect the motor drive belt and rotate the shaft manually to get a closer look at what is happening mechanically? It's very hard to see what is going on in the selector area with the shaft spinning so fast. By the way, my drive belt is somewhat loose. Is there still a source for these? Or maybe an adjustment for tightening? Thanks, Bill