Hello,  Back in the 1970s and '80s Player Piano Company (PPCo)
manufactured high quality music roll frames for "A" and "O" roll
machines.  I have seen many, and have generally found them to be
very reliable.  A client of mine here in Connecticut has one on an
"A" roll build-up machine.

Recently, the speed has begun to vary at times all by itself.  I have
examined and checked the braking system, and have found that the brakes
are not causing speed issues.  Has anybody had this problem, and if so
are new electric motors and or speed controls available?  Thank you in
advance.

Herbert Lindahl
South Windsor, Connecticut
http://www.herblindahlpianotuning.com/ 

 [ Music roll frames built by PPCo and MSI frequently employed a Dayton
 [ gearmotor, part no. 3M153, 20 RPM, 115V, 60 Hz, 0.3 AMP.  This
 [ gearmotor drives the take-up spool of the MSI roll frame pictured
 [ at http://www.mmdigest.com/Gallery/Tech/SpoolF/gloeggler.html 
 [
 [ The speed of the Dayton 2-phase 2-pole induction motor is varied
 [ over a narrow range by a 500-ohm wire-wound rheostat and a diode.
 [ Maybe in your client's machine the rheostat or the connections to it
 [ are faulty (crystallized solder joints, for example).
 [
 [ The gearmotor is still produced by Dayton and sold by W.W. Grainger at
 [ http://www.grainger.com/Grainger/DAYTON-Parallel-Shaft-AC-Gearmotor-3M153 
 [
 [ -- Robbie