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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    A little more info if it helps any, both of these are v1.9 boards but they have the updated 100pf/300k RC network on the 6219's, but I don't believe that is where the fault lies as both were modded at the same time and only one fixture has the issue (also both are running v4.2 firmware since they have the updated RC network).

    The one with the problem you can feel the motor 'kick' if you put your finger on the color or gobo wheel while running in spin speed 1,2, or 3. So at face value it appears the 6219 is not getting proper information, like it's skipping a couple of bits of resolution. Still continuing to probe with my oscope to try to find the issue.
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  • 0
    A little more info if it helps any, both of these are v1.9 boards but they have the updated 100pf/300k RC network on the 6219's, but I don't believe that is where the fault lies as both were modded at the same time and only one fixture has the issue (also both are running v4.2 firmware since they have the updated RC network).

    The one with the problem you can feel the motor 'kick' if you put your finger on the color or gobo wheel while running in spin speed 1,2, or 3. So at face value it appears the 6219 is not getting proper information, like it's skipping a couple of bits of resolution. Still continuing to probe with my oscope to try to find the issue.
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