
48
Troubleshooting
4. A diode (D2, D3, D4, or D5) may be open causing the
fuse to blow at no load or very light load. This may be
due to high armature current.
5. Diode (D1) may be shorted.
B. If the fuse does not blow, but the motor will not run:
1. The speed control potentiometer (P1) may be open.
2. The rectifier (SCR) may be defective.
3. A Transistor (Q1, Q2, or Q3) may be defective.
4. The filter choke (X1) may be open.
5. The zener diode (Z1) may be shorted.
IV. If the motor runs at high speed regardless of the speed control
potentiometer setting:
A. The rectifier (SCR) may be shorted.
B. A transistor (Q2 or Q3) may be shorted.
250-0021r5_readers.qxd 7/11/01 9:18 AM Page 48