MAC 500 Shutter Alignment

[blackadder]

Hi there

 

Has anyone got any advice on how to successfully adjust MAC 500 shutters? I have followed the user manual but cannot seem to successfully align the shutters so they function correctly. The closest I have got is they work fine slowly but if you run strobe then they get out os step.

 

Many Thanks

 

Mike

[DonkiDonki]

Hi there

 

Has anyone got any advice on how to successfully adjust MAC 500 shutters? I have followed the user manual but cannot seem to successfully align the shutters so they function correctly. The closest I have got is they work fine slowly but if you run strobe then they get out os step.

 

Many Thanks

 

Mike

 

 

Are the shutters start position identified correctly during a home?

If so you may want to check that both shutters are tight and not slipping on their shafts.

Try manually moving both shutters (with power disconected), do both stepper motors feel the same? One could be worn.

(I've never serviced a Mac500, these are just general things I've encountered on other units)

[KevinE]

The way I do it is to first of all disable the lamp (dont just remove it). Then loosen the shutter blade so it's still firm but can be moved with a light tweak of the allen screw that wont disturb it. Do a reset, and send blackout to the fixture either in test or off a desk. Look at the shutter once it's finished resetting. If it's in the correct backout position, send it to open and check it doesnt hit the far stop. If its all ok, tighten the screw fully and do another reset to check. If not, black it out again and adjust the blade (important not to move the motor shaft here) so the blade is slightly closer to the reset stop but still blacked out, then try again. This method assumes the motor and drive are ok and it's just a blade vs. motor issue.

 

Its important to know that there are several distinct steps (combinations of drive pulses) that a motor receives before the sequence starts again in a given direction. The blade must be 'phased' correctly with the motor shaft so that the blade hits the mech-stop during the correct phase of the drive waveform. This is because (in the case of a 4-step sequence) the blade will be up against the stop for only one of the 4 steps and will 'jump' back for the other three..this is why the shutter 'clangs' during a reset.

 

If the shutter resets fine and goes to open fine and back again, and only 'loses it' when strobing, its a sign the motor is skipping the odd step when operating at high speed. Either the motor's too stiff or the magnetism has faded. Strobing simply increases the likelyhood of the missed step occurring sooner rather than during a simple sequence of dimming or blacking out. If it were a loom fault or drive IC, the shutter wouldn't dim or open-close correcgtly at all and the shutter action would appear erratic.

 

:D

[djandydee]

Its important to know that there are several distinct steps (combinations of drive pulses) that a motor receives before the sequence starts again in a given direction. The blade must be 'phased' correctly with the motor shaft so that the blade hits the mech-stop during the correct phase of the drive waveform. This is because (in the case of a 4-step sequence) the blade will be up against the stop for only one of the 4 steps and will 'jump' back for the other three..this is why the shutter 'clangs' during a reset.

 

 

at 1.8 degrees per step the motor would find a home position that would still allow the blade to completely cover the beam even it was out by a full step either way (+/- 3mm). For the shutter to be out so far after a strobe suggests a fault condition rather than a fine alignment.

 

It is correct to say when the motors get old they loose strength and slip phases. Since the control board has no active feedback of the shutters position, it relies on the initial home reset and counts pulses. Even at full speed it never looses count so your problem is most likely a bad motor or less likely a bad driver chip.

 

If the motor seems dusty or dirty, it is possible to dismantle it and clean the rotor and stator although in only 10% of the cases, that has worked for me. If you have a spare mac try swapping the motor.

[KevinE]

at 1.8 degrees per step the motor would find a home position that would still allow the blade to completely cover the beam even it was out by a full step either way (+/- 3mm

 

But this isnt how it works. It has to be phased on the shaft so that the correct step during reset is the one that coincides with the hard stop. And you've got 4 to choose from during a reset. If it hits the stop at the wrong step, the other steps received by the motor will cause the blade to be in the wrong position once the reset has finished because the wrong steps can then cause the blade to jump backwards by 3 or more steps as they'll be out of sequence in the drive waveform.

[djandydee]

yes I agree but it would still only be out by a few mill. This does not explain why the OPs 500 is completly out of sync after a strobe. His motor is shagged

[KevinE]

Because if they are only slightly out, they can touch the mechstop at one end or another, not always a problem during dimming but if strobing, they can skip a step as they crash into the stops more violently. You can tell if this is the problem by strobing in a quiet room and listening for any 'clanging' or clacking noise at strobe frequency.

[blackadder]

The way I do it is to first of all disable the lamp (dont just remove it). Then loosen the shutter blade so it's still firm but can be moved with a light tweak of the allen screw that wont disturb it. Do a reset, and send blackout to the fixture either in test or off a desk. Look at the shutter once it's finished resetting. If it's in the correct backout position, send it to open and check it doesnt hit the far stop. If its all ok, tighten the screw fully and do another reset to check. If not, black it out again and adjust the blade (important not to move the motor shaft here) so the blade is slightly closer to the reset stop but still blacked out, then try again. This method assumes the motor and drive are ok and it's just a blade vs. motor issue.

 

Its important to know that there are several distinct steps (combinations of drive pulses) that a motor receives before the sequence starts again in a given direction. The blade must be 'phased' correctly with the motor shaft so that the blade hits the mech-stop during the correct phase of the drive waveform. This is because (in the case of a 4-step sequence) the blade will be up against the stop for only one of the 4 steps and will 'jump' back for the other three..this is why the shutter 'clangs' during a reset.

 

If the shutter resets fine and goes to open fine and back again, and only 'loses it' when strobing, its a sign the motor is skipping the odd step when operating at high speed. Either the motor's too stiff or the magnetism has faded. Strobing simply increases the likelyhood of the missed step occurring sooner rather than during a simple sequence of dimming or blacking out. If it were a loom fault or drive IC, the shutter wouldn't dim or open-close correcgtly at all and the shutter action would appear erratic.

 

:blink:

 

Hi

 

I think this must be a more sinister problem, the driver chip for the shutters keeps blowing... I have changes the shutter mechanism to rule out motors, I have changed the motherboard so I suspect I must have some form of loom fault? I have continuity tested the lines to the shutters and all seems ok ie connection fine and no shorts. But I guess there could be a short across to another circuit? Not sure best way to proceed. Any tips appreciated.

 

Regards

 

Mike

[marktownend]

If the driver chips keep blowing, it sounds like a short(s) on the wiring loom. Test this by not just checking for a short to ground, but by doing so as you move the head for the whole of its pan and then the tilt range, both backwards and forwards. Use a meter with an audible beep, and check each individual wire for the shutters.

 

Reason being, if there's a tiny spot of insulation worn away (and believe me, it happens quite often) with the movement of the wires within the unit as the head is moved around, the worn spot will not always touch earth, and may only do so at 1 tiny point in the movement. Of course, if you're unlucky, it'll only do it when the head's upside down rather than on the bench!

 

Be careful when you're doing this to keep the meter probes touching at both ends all the time, as it's very easy to find they've moved and there's no way then that you'll hear a beep!

 

Hopefully this will enable you to find a fault and determine which section of loom will need replacing (or bodging...). If you're getting a beep during the pan movement, then it's the awkward loom between the PCB and the arm; if it beeps during the tilt movement it'll be the slightly less awkward loom between the arm and the motor.

 

Once you've found the fault(s) then you'll need to replace the driver chip again. There's an advert in the Classified section of the forum for them ;-)

 

Hope this helps,

Mark