The run motor is a non-self-starting synchronous motor. Rather than delivering a constant power, it delivers a series of pulsations, one for every half cycle. That would be two pulses per cycle and 120 pulses per second with a 60 cycle current source. RPM is 1200 for 60 cycle motors. 1500 for 50 Cycle.
These motors do not usually have many problems. If your organ is having problems running you might suspect the run motor as having a problem. To be certain you must make sure it’s not a sluggish generator or a problem with the start motor not getting up to speed. Once you determine it’s the run motor, you need to determine whether it’s mechanical or electrical. The most common problem is the motor becoming sluggish or stuck from low oil.
Make sure the threads are in place going to each bearing.
From the oiling “tub” there are threads that go to each motor bearing. These threads provide the motor bearings with oil. There should be enough oil in the “tub” to make the felt moist which will supply the bearings via the threads with oil.
Make sure the motor spins freely.
To check the motor separate from the generator you must remove two springs that couple the motor to the generator. Once removed, you may spin the motor or generator independently.
If the motor is stuck, apply oil directly to the bearings and turn it by hand until it becomes free. You can also help free it up by pushing the shaft in and out.
You may have to remove the vibrato scanner to access the rear bearing but a carefully placed drop of oil can be directed to that bearing. Also soak the threads.
It should be free enough to spin so that it will gradually slow down and not stop immediately.
Checking the two coils in the run motor.
There are two field coils with four wires, two red and two black. Each pair of red/black wires go to one coil. It is possible for a coil to fail causing the motor to lose it’s normal power. In some cases it may still run but be very unpredictable.
The other pair of motor wires are connected to the seventh from the left or the right most terminal.
Now each motor winding has approximatlty 180 ohms of resistance. This means that the two fields in parallel would read 90 ohms. So if you measure the two terminals which connect to the run motor you should read 90 ohms if both coils are OK. If you read 180 ohms, then one field coil is open. If you read infinity, then both coils are open. Replace the motor.
All 60 cycle run motors are the same and you can use one from say an M series spinet organ or equivalent.
This information is for educational purposes only and no claims are made that this information will lead to any successful repair. Benton Electronics assumes no responsibility to its use.
|Hammond Generator Start Motor||Tone Wheels|
|Hammond Generator Start Motor|