I recently bought an M3 for $50 and am trying to get it running. After a lot of oiling and waiting, it spins up fine, but as soon as I hit the run switch it stops turning immediately. There is no resistance measured across the 250 ohm resistor R9.It is a wire wound resistor and I am not sure if I go to Radio Slack and get a 250 ohm resistor to replace it, will it work? What wattage is required? Does it need to be a wire wound replacement?</P>
Yes, use a wirewound resistor. This has to do with the heat capacity during surges. If you can photo it with a size reference alongside I can probably estimate the power rating...</P>
For instance, one wond on a 1/2 inch ceramic tube that is 1.5 inches long would be about 25 watts, one that is 3 inches choose 50 watt size...</P>
From Raadio shack the best you can do is 5 of part # 271-133 in series... not a very clean arrangement...</P>
Try part # TMC50-250-ND from DigiKey.com. It is an aluminum housed high quality reisistor. 250 ohms, 50 Watt</P>
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I looked at the schematic. I believe the resistor is actually R90 rather than R9.</P>
It drives a little bit of current into the starting motor when in run mode. During starting, the resistor is shorted out and should read zero ohms.</P>
If you unsolder one lead, it should read 250 ohms plus or minus 10%.</P>
A 50 Watt resistor would handle worse case, athough even a 25 watt would have adequate safety margin. The DigiKey part I gave you should work fine.</P>
I unsoldered one lead and it does in fact read 250 ohms. Hmmm...</P>
The problem is that the start motor spins up fine, but as soon as I hit the run switch it all freezes... just stops completely... doesn't slow down, just stops dead. What could possibly cause this?</P>
I kind of suspected this... that is why I had you unsolder a lead...</P>
I want you to do several tests:</P>
1. Measure resistance of the run motor winding. Disconnect the leads to do this to avoid sneak paths.</P>
2. Measure the voltage at the run motor input with the switch set to run.</P>
Here are some possibilities:</P>
1. The start speed is insufficient to allow the syncronous run motor to lock in.</P>
2. The run switch does not connect voltage to the run motor.</P>
3. Bearings in run motor bad so that rotor grabs pole pieces magnetically when power is applied... bearings are replaceable...</P>
4. Windings in run motor are open circuit. </P>
5. Sometimes motors like the start motor may disengage when power is removed. If it is supposed to and doesn't, that would be the problem. Often this is done by the shaft sliding endwise to mesh gears against a return spring. When power is removed, the rotor is pushed back by a spring to disengage.</P>
Check possibility of 1. and 5. first... could be gummy bearings in start motor.</P>
Apparently the run motor has two coils then? If so, then those readings are about right.</P>
Is it obvious how the wires connect? If one of the coils were reversed by someonethe action you describe would result.</P>
If there is a possibility that someone reversed the parallel connection, you could try reversing one of the pairs of windings and do a <U>brief</U> test.</P>
The motor may have two windings that can be connected in series for 240 volt operation or in parallel for 120 operation.</P>
The schematics do NOT show two windings.</P>
How are the leads labelled? if it is 1 and 2 and 3 and 4,then I would expect 1 and 3 connect to one power lead and 2 and 4 to the other.</P>
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The schematic I have shows a black & red attached to terminal 4 and a black & red attached to terminal 7. This is what my M3 has. The resistance checks out ok. Looking at the wires from the motor to the terminals, they are not long enough from the 4th terminal to reach to the 7th, so I doubt they were reversed at some point. They aren't labeled in any way I'm now leaning toward the switch not providing power to the run motor. This is just a double pole double throw switch, correct? Can I get one from an electronics store and replace it? It isn't a special Hammond switch or anything is it?</P>
One thing that I learned in the first few days of owning my M3, is that they require a LOT of power to power up. To be VERY specific if I were to plug my M3 in the garage, it would shut down just as you describe. Because my garage outlets tip-off at 15watts. </p>
To start your M3 you'll need a GOOD 20+ watt hookup. This sounds silly, but its true. If you live in an appartment, pull out your refrigerator, and plug that M3 in the same outlet as the fridge. </p>
An old M3 (or any Hammond that hasn't been run awhile) needs to pull huge current to get the sycnch motor going after the asynch-motor kicks in): it can and WILL draw about 20+ amps.</p>
What I did with my M3 when I got it was to plug it into two huge extension chords off a true pair of 20+ plugs. Once you get it going, and it gets the oil and settles down; ... you'll find that it will start up with about 5 amps or less.</p>
Especially read about the strating motor... It apparently spins up faster than syncronous when you hold the start switch. While holding the start switch, you go to run then release the start.</P>
The start motor DOES disengage by sliding endwise when no power is applied to it. Make sure yours in fact does this.</P>
If speed at start doesn't get ABOVE the syncronous speed and fall back as described at that link site, then it will stop as yours does...</P>
This could be a lubrication problem as the start motor under excess load would "slip"" too much and run too slow.</P>
If you can warm the amplifiers first, you might be able to tell by firing a note and see if it is below pitch... if it is, then motor is too slow... I would estimate that during start the notes when sounded should be at least one or two notes above normal pitch since generator is spun faster at start.</P>
15 watts would not be enough to hardly run a synth... you probably meant "Amps"</P>
Frankly, as an electrical engineer, if you are having trouble running an M3 from an outlet fed by a 15 amp breaker, you may have serious or even unsafe electrical problems in that garage wiring. I would do a couple checks with a voltmeter and a load to check it for safety.</P>
Possible causes of problems may be excessive length from the breaker box, loose terminals, bad splices... Those push the wire in the back receptacles are notorious... don't use them... use the screw terminals on the side.</P>
Put a load on this plug, say a 1000 watt heater and measure the voltage... If you find less than say 115 volts, measure it without a load. If you have more than 5 volts difference between loaded and unloaded, investigate the problem... IMMEDIATELY !!!!</P>
This regulation test will point out bad connections, etc. and possible safety hazards.</P>
I have seen imminent failures in breaker boxes... One that was in a rental house cause whole place to burn down... landlord was warned and did nothing. Many houses using aluminum wires bringing the power into the breaker box have not been properly done. Aluminum wires take special handling and oxidation protection... The metal cold-flows and gets loose and then heats, oxidizes, then heats more until it fails with flames...</P>
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