It's an FG servo, but you will be blazing new trails with this one. Take careful notes and pics, in case you are successful. Good luck...
Well, I sort of succeeded. I got the motor running again, but I was using to high a voltage to test it (using a 14 volt cordless drill battery) and I released the dreaded white smoke. Smelled like a resistor, and there is one in the end cap in series with the brushes. That was stupid of me. I think this motor usually runs on around 9 volts.
Here's what I found out:
1. The outer shell comes open with three screws The internal motor is held in place by both a front and back silicon vibration extrusion. There is no mu-metal shield, I guess the outer shell serves this function.
2. This exposes the internal motor, which also has its' end cap held in place by three screws. The motor power wires go into the motor through the end cap. The FG wires go down to the front (taped to the motor outer shell) and into the motor near the front on the side. BTW, no part number on the internal motor case.
3. With the end cap released, the motor easily comes apart. The fg coil is attached inside the case up at the front between the front of the can and the magnets. There is another magnet wheel mounted on the shaft (on the front side of the windings that spins inside the FG coil assembly when the motor is assembled).
4. The motor is a standard, 2 brush, commutator DC motor. There is a small electrolytic cap across the brushes, and a resistor in series with the motor power wires.
5. Looks like about 8 or 10 segments on the commutator. It was really black and burned looking.
6. The rear bearing is a cup bearing in the end plate, with a nylon washer and a flat oil retaining felt washer.
I had no problem putting the armature in my handy variable speed drill and using a burnishing tool (I didn't have any emery cloth or really fine sandpaper) cleaned up the armature. It looked pretty good after that. (I had a couple of dead spots in the rotation before I started).
The brushes are a little worn, and there was a lot of brush dust in the end cap. I cleaned that out with canned air, lubed up the bearings, and re-assembled the unit in reverse order.
The motor ran much stronger until I released the smoke. I'm going to take it apart again tomorrow and see if I burned up that resistor. It was already so burnt when I first opened the motor that I couldn't see what value it was. (I think it is a resistor)
After the smoke, the motor was completely dead. I figure at this point I've nothing to lose.
BTW, on my "parts" deck, I found the Control B problems and replaced a regulator, NPN pass transistor, and a 24 volt zener diode. The machine now works except for the capstan. Oh, and looks like I'm going to need a new reel motor. The supply side has significant wobble, I guess due to shipping damage. It's not very bad. I may take the rubber mallet to the shaft and see if I can straighten it, but I know this is probably a lost cause.
The deck plays audio (in both directions) if you spin the reels by hand (I don't have any pinch rollers on it right now), though the speed is highly irregular in "finger capstan mode".
David