In response to Ian McLaughlin's posting about the drive system of
a Kimball Electramatic, I just recently repaired one of these and
I thought I'd share my findings.

The system for roll transport in this player (about 25 years old) used
two separate gear motors, one geared for 'play' operation, and the other
geared up higher for rewind.  Each motor was directly connected to the
spool with no transmission as in typical players.  There is, however,
a clutch of sorts that is intended to disengage the motor when power
is not applied.  The motor is of the 'synchronous induction' type found
in many phono turntables (remember them?) .  Its armature is set in its
bearings in such a way that it can float and move laterally about 3/8".
It is this movement that allows the motor to disengage itself from the
gearbox.

Here's what happens.  The oil in the motor bearing dries up, and the
armature shaft has trouble disengaging.  Now you've got a situation
where both the play and rewind motors are connected to the spools.
With a roll in place, there's no way one motor can spin the other one
due to the high gear ratios, even when one isn't powered.  So the motor
sits there stalled out, and it doesn't take long for this to overheat
the motor and quickly open its windings.

The key to keeping these happy is to keep those motor shafts lubricated
and free to move laterally, so that the clutch works consistently.  To
you, Ian, I found a replacement motor from fellow MMD'r Ed Gaida in
Texas.  Keep your eyes open in the surplus electronics market.  Had I
not found the part from Ed, I was looking at using the remote control
tuner drive assembly out of a 1974 Motorola Quasar TV (like an Ampico
works in a drawer), which had a very similar gear motor in it.

Eric Bergstrom
Saint Charles, IL