Hi All,  Craig Brougher brought to my attention the fact that the
original roll frame speed control design called for a wirewound
potentiometer.  PPCo later opted to use a cheap carbon pot.  Craig
also noted that the only reason the speed control worked with the
cheaper pot is that it's in parallel with a 6 ampere diode, which
he suggested should also be replaced with two similar diodes, just
to be safe.

Musically,
John A Tuttle
Player-Care.com
Brick, New Jersey, USA

 [ A suitable 5-watt wirewound potentiometer, 500 or 1000 ohms, is
 [ available at http://www.mainelectronics.com/potentiometers.htm 
 [ part no. 26TBL500 or 26TBL1K.  -- Robbie