Trackspot motors 'surging' / 'hesitating'

I've got a Trackspot that has a very odd problem, it is affecting every motor in the unit. When you rotate or pan/tilt at slow to medium speeds every motor will hesitate or surge (depending on how you look at it) while moving. This happens about every .5 / .75 seconds.

My initial thought was one of the data busses feeding the 74373 latches was hung therefore unable to step through all the bit resolutions but checking with a scope I find both the data inputs to the latches and the outputs to the motor drivers all functioning.

I've also swapped the uProc and the Eprom with a known working fixture and the problem stayed with the fixture.

5v and 24v supply rails look good, good voltage, no AC ripple.

I give... any ideas? :confused:
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    Just something to check. I had a similar, but more intense, problem on a Trackspot that hit my shop recently. It was only one of the motors, the gobo wheel motor, but it jumped around like crazy rather than moving in any particular direction. I went crazy probing the logic driving the latches, and the output of the motor controller chips. Finally, I noticed while disassembling the unit to try to replace that motor (thinking that it must be the motor) that the wires running to that motor had gotten pinched, by a previous reassembly, and were making intermittent contact. The wires were hidden in the little tunnel that protects them from the lamp heat, so I assumed they must have been OK, but it turns out that was the problem.

    I'm not saying this IS your problem, but it's something to check.

    Jeff.
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  • 0
    Just something to check. I had a similar, but more intense, problem on a Trackspot that hit my shop recently. It was only one of the motors, the gobo wheel motor, but it jumped around like crazy rather than moving in any particular direction. I went crazy probing the logic driving the latches, and the output of the motor controller chips. Finally, I noticed while disassembling the unit to try to replace that motor (thinking that it must be the motor) that the wires running to that motor had gotten pinched, by a previous reassembly, and were making intermittent contact. The wires were hidden in the little tunnel that protects them from the lamp heat, so I assumed they must have been OK, but it turns out that was the problem.

    I'm not saying this IS your problem, but it's something to check.

    Jeff.
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