Seized DR needs a Jenny

Hi Thomas.  In general, DR machines are not likely to become stuck unless there is damage already occurred to the machine. The exception is when they sit for very, very long periods of time. If it was running and all of a sudden became stuck, the prognosis is not good. Not saying to give up, though. 

I have done some videos of un-sticking CA machines using a rotary converter which I am assuming is what you mean by a "Jenny" (or generator.) There is no commercial product like this. You will have to build your own if you decide to go down this path. There are some inherent risks to using such a machine. I would not want to advise on this build unless I had an electrical drawing in front of me to use for reference. I built mine bespoke and don't have a diagram. Some day I plan to build it into a nicer housing and have switches to select between the different boost modes. At that time, I will make a diagram. For now I will only explain the principle but not attempt to explain how to assemble it.

The basic principle is that you have one motor "running already" and then you connect its Common, Main, and Start circuits to the stalled compressor's Common, Main, and Start circuits. By making this parallel connection between the running and stalled motors, the stalled motor will receive two separate voltage waveforms, out of phase, in the manner required to produce boosted starting torque. All starting components of the Monitor Top control need to be out of the circuit to do this procedure. It needs to be just the converter motor and the compressor motor. You can produce forward and reverse torque with this sort of converter, based upon how you wire the converter motor's start winding. It is hard to know which way you are spinning the compressor, so it is a good idea to only boost for a fraction of a second or so. Then try a "normal" start. 

My setup allows selecting between 120V and 240V power to the compressor; as well as switching on and off the "S" circuit from the converter motor to the compressor motor. You can switch voltages instantly so that if it takes 240V to start the compressor, you can give it that, and then switch down to 120V while it's still running before it can come to a stop. The CA compressors when they get "tight" often need this sort of treatment to get them to continue running after they have been boosted and re-activated from being stuck.

It's easy to get confused between the CA machines and other models. The CA machines are the 1933 and 1934 models, which used methyl formate refrigerant. These have a series of issues which cause them to get stuck, without underlying damage. These are often very repairable.  All other models normally never get stuck; and if they do the prognosis is not good. 

The DR machines which sit for a long time can get stuck; however there is a higher likelihood that the starting system is at fault, instead of the compressor. Can you give us more details on your DR? Particularly the machine size (DR-1 / DR-2 / DR-3 etc.) and share some pictures?

The smaller machines use a starting resistor in the control. This resistor can burn out, leading to a no-start condition. The larger machines were polyphase motors with a transformer-capacitor device which was used for starting and running. This can fail and make it appear that the motor has burned out when in fact it is not the motor. The transformer-capacitor device can burn the motor if repeated start attempts are made with it in a damaged condition. 

Please let us know about your machine and there are several here who can give better advice!

Sincerely,
David

Anything is possible! He needs to be very careful; and ensure that he understands what is required to make this test / procedure happen safely.