Beogram 4002 DC Platter Motor: Some Microsurgery on Disconnected Pickup Coils

I recently received a DC platter motor from a Beogram 4002 in Norway for some TLC. The customer already had done the 'oil infusion' process for the Oilite bearings, but after he put the motor back together and into the Beogram, the platter speed was much too high and could not be regulated anymore.

This shows the motor as received without pulley:

Runaway speed of a DC platter motor is a fairly sure sign (in absence of issues in the motor control circuit) that one or both of the RPM feedback pickup coils in the motor had been disconnected during the extraction/re-installation of the bottom bearing. This can easily be checked: Just connect a Ohm meter between the red and white leads on the plug, and if you measure an infinite resistance then one or both  coils are damaged:

If everything is alright the measurement should yield something between 35 and 45 Ohms. This varies across the various motor generations that were used. I opened the motor up and extracted the brush carrier that also holds the two pickup coils:

If you look closely, you will see the small disconnected wires on either side. Once this happens, a bit of microsurgery is needed. Basically one needs to unwind some wire under a microscope until about 15-25 Ohms can be measures between the two ends of the coil. Unfortunately, in this case this seemed to have been already tried, and the coil windings were cut to some depth. So I spent a bit of time with unwinding, tinning the end with solder (the wire is 'magnet wire' i.e. there is a coating on them that needs to be evaporated and replaced with solder before one can measure resistance reliably), measuring OC, unwinding until the wire piece fell off since it was cut off, and then anew. After a while I finally reached the still connected end and measured the proper resistance:

The wiring that I removed:

On the other coil it went similarly. Once this one was recovered, too, I put them back on the brush carrier.

This is the resistance I measured between red and white wires:

Then I reassembled the motor, installed it in one of my Beogram 4002s and measured the RPM with my BeoloverRPM device. This is the curve I measured:

This is as good as it gets with the Beogram DC platter motor! This motor is back in business!