So, I got this Hammond M-2 tonewheel organ in trade for some labor. The power cord was almost rotted off. So I replaced it with a generic power cord from local hardware store.
So, going to start it up finally, the starter spins but only catches about half the time. That isn’t the real problem though. After the starter catches, I turned on the run switch, and could hear the amplifier warming up. If I continued to hold the start switch, I could hear the tone generator but the sound was out of tune and sickly sounding. But if I released the start switch, the tone generator slowly ground to a halt with a gradually decreasing pitch.
Based on the M-2 reference manual and Hammond stuff on the web, I suspected a problem with the run motor. The run switch was working because the amplifier was coming on. No motor was seized because the TG shaft was spinning freely (and could be spun freely by hand).
I unplugged the power cord, removed four screws from the shield near the middle, and loosened four screws at the top of the shield, and removed the shield. The scanner (round thing with screws around the edge) and run motor are on the left. The run motor turns the scanner with a gear that penetrates the scanner housing. The run motor turns the tone generator shaft through a ball joint plate anchored by 2 springs to the tone generator’s flywheel.
To test the run motor, desolder the two wire pairs (rightmost terminal, and fourth rightmost terminal). Use an ohm meter across the two pairs. If the ohm meter reads zero, then at least one motor winding is shorted. If the ohm meter reads non zero, then your problem is elsewhere, perhaps bad solder at the switch or at the motor terminals. My ohm meter read zero, so I knew the motor was toast.
I acquired a used run motor for $20 on the HAMTECH list. When it arrived, I tested it to make sure it was not shorted, and then proceeded to install it.
I first removed the 4 nuts attaching the run motor to the floating TG cradle. Then I was able to disengage the run motor shaft coupler from the TG shaft and remove its two springs. Finally, remove 3 screws that couple the vibrato scanner to the run motor, and separate the two pieces, being careful not to break any oil wicks that are not already broken.
Now, what can be a real problem is those old oiling wicks. They are made of cotton thread and over time simply decompose. There are two wicks that enter the vibrato scanner housing, and one wick oiling the shaft on each side of the run motor. All of these wicks need to be intact, and have one end in the oil tub on top of the run motor. I repaired these broken wicks by going to the store and buying a spool of 100% cotton thread, then tying a piece of new cotton thread to the broken piece of wick. (This is easiest by first making a loop with the new thread, then placing it around the broken wick and pulling it taut.) Then, to get the wick into the oil tub through the passages, use a needle to start the thread into the passage, then a small straightened paper clip to finish ramming it through. Do not pull the knot into the passage.
Then finish reinstalling the 3 screws that couple the vibrato scanner to the run motor (installing the oil tub onto the new motor at the same time). Reinstall the run motor to the shaft coupler with the 2 springs, then simultaneously engage the coupler to the TG shaft while aligning the 4 run motor studs into the bracket holes. Push it together, and reinstall the 4 nuts.
Solder the run motor wire pairs to the same terminals you removed them from (the polarity is irrelevant). Use a low flux solder and make sure the terminal is thoroughly heated so you don’t get a cold solder joint.
Plug in the organ (being VERY careful not to stick hands, tools, etc into the exposed area since live AC is in there), and test it by starting it and flipping the run switch. Mine worked perfectly immediately. Reinstall the shield, tightening all the screws, and pat yourself on the back!