Martin mac 500 repairs

[FrankT]

Hi there 

I am new here, so I hope this is the proper way to ask my questions , I am also not a native english speaker

I am trying to repair a few mac500, cleaned them and some of them I got sort of working.

I saw that the colour wheels have magnets to detect their position

the rotary gobo however has what they discribe in the service manual as a mechanical index. I get a rger on that fixture so I guess there must be a problem with the detection.

can anybody tell me how the mechnical detection functions ?

Edited November 1 by FrankT

[DrV]

It's been a long time since I looked at one of those but it probably works by having an end stop. In other words on reset the wheel is wound all the way back until it won't go any further and then that is taken as the index position. That's certainly the way the shutters work.

[sunray]

13 hours ago, DrV said:

It's been a long time since I looked at one of those but it probably works by having an end stop. In other words on reset the wheel is wound all the way back until it won't go any further and then that is taken as the index position. That's certainly the way the shutters work.

It's knocking 30 years since I worked on Martin products, I recall some wheels worked that way on some series, I remember there being differences between 200 and 800 series, some had magnets, some had light sensors and other knocked hell out of an end stop but which and what has long since faded into oblivion.

One fitting in particular was very noisy as its wheels would return to start for any change, so say there was 12 positions and it was on the first, the stepper motor would make it clatter against the stop 12 times before attempting to send it to its new position. If it had 3 wheels (but I don't recall if any with 3 used this system) that could be 36 hits and a bar full of similar fittings...

[FrankT]

I have the error RgEr on this Mac500, according to the manual this error is displayed after a time out. After startup  I can hear and see the rgobo disk rotating until it hits the mechanical stop, it hits the mechanical end a few times but than it stops, I thinbk than the colour wheel starts rotating . A bit later the gobo figures are still rotating. so maybe the timeout is generated because of this.  

[DrV]

So there must be a magnetic sensor on whatever rotates the gobos to allow them to be projected the correct way up. IIRC there's a gear in the centre which rotates them and there might be a magnet on that with a corresponding Hall effect sensor (that looks like a small TO92 or E-line transistor). The alignment of that will be important. (And whether or not the magnet has fallen off!)

But then again, I haven't looked at one for over 10 years and I may be thinking of a completely different fixture. I might have some notes or even a pic but haven't got access to them until Monday.

[indyld]

I can't remember the 500 as it was too long ago, but most gobo rotation mechanisms have a magnet - there can't be an end stop because the rotation is endless.

On other fixtures, the magnet can be on one gobo holder itself which needs to be in the right place on the wheel. I don't remember the 500 having removable holders, as I recall changing gobos in position on the wheel. With that said, I've had this type of error on more recent spots when the holder has been put back in the wrong slot meaning the one with the magnet is not in position during boot.

This does sound like a similar issue, the fixture can't find where the rotation is and times out. 

[FrankT]

Ok I found the service manaul and the Rotating Gobo wheel has a mechanical index, so no magnetic detection. I also checked the schematics there are only 3 hall modules GOBO2 COLOR1/COLOR2/GOBO1 (=fixed gobo). I wonder how the software of the steppermotor detects the mechanical stop? because thet could be the problem. 

[DrV]

11 hours ago, FrankT said:

Ok I found the service manaul and the Rotating Gobo wheel has a mechanical index, so no magnetic detection. I also checked the schematics there are only 3 hall modules GOBO2 COLOR1/COLOR2/GOBO1 (=fixed gobo). I wonder how the software of the steppermotor detects the mechanical stop? because thet could be the problem. 

The point about a feature with a mech. stop is you don't detect it. If the wheel needs, say, 100 steps to make a full rotation, the processor sends 110 steps on reset which guarantees that by the end of it the wheel will be against the stop. From that point onwards the processor 'knows' the position of the wheel and tracks it by counting steps in each direction. If the power goes off the processor 'forgets' the position and has to do another reset sequence to find the position again. So you can't get a feedback error from a feature with a mechanical stop.

It's the same with the shutters. With the power off move them by hand to a half way closed position then watch as the power goes on - they step all the way open against their stops and keep on stepping because the processor is ensuring that they are fully open, regardless of where they started. Thereafter if you ask for 50% closed they will step to that position because the processor sends the right number of steps. But it can't tell whether they really are at 50% - it just assumes so.

 

[FrankT]

Thanks DrV for this explanation, I was getting confused because the previous owner had placed a magnet in the RGOBO wheel in one of my MACs. I took out the magnet the lamp still gives the RgEr (timeout error) after reset, but it seems to be working. I will look closer at the installation/removal of the Rgobo wheel in the service manual and run some tests in manual mode. 

 

[sunray]

3 hours ago, DrV said:

The point about a feature with a mech. stop is you don't detect it. If the wheel needs, say, 100 steps to make a full rotation, the processor sends 110 steps on reset which guarantees that by the end of it the wheel will be against the stop. From that point onwards the processor 'knows' the position of the wheel and tracks it by counting steps in each direction. If the power goes off the processor 'forgets' the position and has to do another reset sequence to find the position again. So you can't get a feedback error from a feature with a mechanical stop.

It's the same with the shutters. With the power off move them by hand to a half way closed position then watch as the power goes on - they step all the way open against their stops and keep on stepping because the processor is ensuring that they are fully open, regardless of where they started. Thereafter if you ask for 50% closed they will step to that position because the processor sends the right number of steps. But it can't tell whether they really are at 50% - it just assumes so.

 

You have explained that so much better than I

[jamieshurlock]

to ad to this, the gobo position is just an end stop time out but there is another hall effect sensor on the opposite side to the other 3 - this is for indexing the gobo position. so it will select the gobo as normal, rotate them etc but flash up the error as the sensor is not seeing the magnet on one of the gobo holders..... 

if you need parts or tech support email sales@jamiesmagitorch.co.uk

[FrankT]

Thanks Jamie, I found that one also.

I have now 3 out of 9 fixture working, one had a broken wire from the tilt switch, which was a challenge to replace.

I bought a small light mixing table with 16 channels, I can control the gobo’s pan tilt etc, except the light channel doent work (dimmer, shutter , lamp off) any tip what could cause that ?

gr frank