Antique Turntables

I recently purchased an antique Stereo Cabinet/System. It is branded Stromberg Carlson, but was built my General Dynamics. The Cabinet and components are visually flawless and look as if it was built yesterday. Since the unit is at another location being repaired I don’t have any more access to more details of my unit. I believe it was built in the late 50’s possible into the 60’s. I have all of the original documentation with the unit at the repair facility, several miles from my home. The only information I can provide at the moment is below.

It is a Tube amp with a Preamp as well as a Turntable. I knew it needed work, so it is being repaired as there was a nasty hum and the turntable would not work. It is now several weeks later and the Amplifier has been repaired by replacing a badly leaking Cap, so the hum is gone as well as the crackle from all the dust cleaned out from the inside of the Pots for Volume, Bass, Treble and balance.

The turntable is receiving power but the mechanisms in the turntable changer that engage with the motor are just frozen. So the only way to return the Turntable to functional condition is a donor table to replace the frozen parts or an outright replacement. I would like to keep the unit original.

The model number of the Turntable is a Stromberg Carlson PR520 or lower end PR510, apparently the Turntable was also sold under several other brands as well. One of the other brands model # is Glaser-Steers GS-400.
I would appreciate any input into locating a suitable Turntable replacement or Donor Turntable.

John