MAC250 "goer" Error

[bishopthomas]

I have a MAC250 giving me a Gobo Error message. Upon bootup the gobo wheel tries to move but just stutters in place. I can rotate the wheel freely and also rotate it via the motor axel, so it doesn't seem to be a motor issue. I swapped sensors with the color wheel and still the same problem, so it doesn't seem like a sensor error. I cleaned the magnet on the gobo wheel. I tested continuity in the wiring harness and even swapped cables with the working color wheel.

I'm out of ideas as to what to look for. Any thoughts?

 

[joeboo46]

Have you tried going to the control card and making sure nothing has come loose there? Even tried just unplugging and re-seating the harnesses on it.

Also make sure the magnet is passing in line with the sensor (within a fingernail thickness) is the way i usually judge it, and also make sure the sensor is square to the magnet.

 

[JD]

The stepper motors are two phase square wave motors. (A grown up version of what used to be used in computer floppy drives.) The symptom you are describing is what happens if one of the two phases are missing. There should be four wires coming off the motor. Two feed one winding, the other feed the second. You can unplug the motor and feel out with a multimeter if one of the windings is open. Unfortunately, many times it is the drive circuit that fails. However, checking the connector and the motor are easy so it's a good place to start.

 

[bishopthomas]

So there should be continuity between two pairs of pins on the connector? I checked the cable harness itself so if this is the problem I guess it lies within the motor. I considered swapping motors but there are so many parts to it that I'd like to save that for last.

 

[TimMiller]

Replace the driver chip. It's a 3775 located in the base of the unit next to where the wire comes off the pcb leading up to the head. They typically unplug out of the dip socket then you just push a new one in.