MINI MILLS - MINI LATHES

Place jumper between 6-7 then check for 120V AC between 4-5, If none then test fuse, power switch and speed potentiometer. Switch contacts on speed potentiometer should read a short when control is rotated full ccw. If 120v is present between 4-5 check for 12V DC between P1-P3, If no 12v is found then board needs repair.

Check for 120V AC at L1 nd L2. If none then check power switch and fuse. Install a jumper from K3-K4.. Watch LED2(Power on) and LED3(Overload) indicators on the board LED3 will briefly flash and yellow LED will illuminate if overload detected. If yellow front panel LED is out when switch is in F or R,  check for approx 6V DC between P1-P3. If none board needs repair.

Be sure green LED is illuminated on power board. If not check fuse and power switch. If motor jerks violently, or requires manual rotation to start then power board needs repair. To test motor hall sensors, check for 5v/0 toggle on SA SB SC reference to common on same terminal strip. CAUTION 350+ volts present on these boards even 10 minutes after power is removed !

Obtain a 9 volt battery and touch the motor leads to the battery terminals. Motor should spin slowly and smoothly. If no rotation or speed is erratic then motor needs repair.

Older Sieg DC motor control boards usually have  4 terminals, 2 for AC in and 2 for Motor out, as well as a 3 terminal connection for the speed potentiometer. There should be 12V DC across first and third potentiometer wires(P1-P3). Mid production boards have 7 terminals per newer boards , but 6-7 are hardwired to the direction switch.

Many of these machines come equipped with poorly designed boards that will burn up on even moderate loads. They are square shaped small boards, and are a waste of $ to fix, contact me for options. Some boards with 5 large chips mounted to a heatsink are OK and repairable.