MH 600 Yoke reset error

[Notsobright]

Hi All

 

I have a MH 660 that does a reset when switched on, the address numerals flash as no DMX is connected and once the unit has done its reset sequence the yoke vibrates quite rapidly.

 

when I connect the DMX controller and set the address the vibration stops but the light does not respond to any DMX commands.

 

When I run it in demo mode the yoke vibrates while the rest of the demo sequence runs.

 

The light developed a fault originally on the head tilt stepper motor which has now been repaired and the filter capacitor gave up the ghost and has been removed and shorted out.

 

I sincerely hope someone can offer some suggestions as to how to narrow down the fault as I am in South Africa and spares here are more scarce than chickens teeth and need to be brought in.

 

Look forward to your comments!

[timsabre]

Are you saying the yoke moves correctly during the reset sequence?

 

It sounds like a stepper motor driver fault, or possibly a problem with the power supply to the motor drive - but the yoke wouldn't move at all if that was the case.

[Notsobright]

Are you saying the yoke moves correctly during the reset sequence?

 

It sounds like a stepper motor driver fault, or possibly a problem with the power supply to the motor drive - but the yoke wouldn't move at all if that was the case.

 

During reset sequence the yoke moves smoothly and stops then runs smooth back to the stop then vibrates against the stop.

[DrV]

That sounds as though the optical feedback sensor is u/s. I think the yoke moves to the microswitch first just using the stepper without looking at the sensor. It then starts movement with reference to the sensor so if it gets no pulses back from the toothed wheel it will just keep going (until it hits the other end of travel). Sensor might be dirty or out of alignment with the wheel.

 

 

Dave

Edit to clarify

[Notsobright]

That sounds as though the optical feedback sensor is u/s. I think the yoke moves to the microswitch first just using the stepper without looking at the sensor. It then starts movement with reference to the sensor so if it gets no pulses back from the toothed wheel it will just keep going (until it hits the other end of travel). Sensor might be dirty or out of alignment with the wheel.

 

 

Dave

Edit to clarify

 

Hi Dave

 

Thank you for your feedback I am going to check out the optical sensor and I shall revert with any further info on what has transpired.

 

Thank you so far

 

Regards

[KevinE]

what was the original fault with the tilt motor?

[gafferted]

A common fault I've come across with these is the Molex connectors to the optical sensor boards corroding and failing to make contact. I can't remember the exact symptoms but I think the the pan or tilt goes very slowly during reset then sits vibrating on the end stop instead of jumping to the centre position. It seems much more common on the pan sensor since it sits by the base fan where all the smoke gunk gets sucked in.

I tend to replace the corroded contact but I guess if spares are hard to come by you could just solder the loom to the pins on the board.