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Author Topic: Movinghead repair problem  (Read 2273 times)

Anders Haggblom

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Movinghead repair problem
« on: October 11, 2005, 04:47:03 am »

Hi all!

Let me start by stating that I'm a sound engineer/service tech. I don't normally work with repairing movingheads. So forgive me if I don't know the correct name of every part I'm trying to describe.

I have a 5StarSystems Spira250 Movinghead that needs repair.

When powering up the unit, normally the panning motor (the horizontal motor located in the base) should go to its end position first and then return to a mid position perpendicular to the base. For some reason, the unit does not always recognise the end position. Instead the motor continues to try and turn the head even if it is not possible. To my understanding the end position is recognised by some kind of magnetic device located on the "arm" piece located directly under the big gearwheel. I don’t think that the problem is in the electronics that recognises the end position, since I’ve tried to exchange the PCBs with the PCBs in a working unit. My guess is that the problem is more of a mechanic nature. Have you heard of any problem that resembles this?

I appreciate any help on how to solve this problem.

Thank You

Anders
Kainos Media
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Ethan O'Toole

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Re: Movinghead repair problem
« Reply #1 on: October 12, 2005, 12:52:32 pm »

There may be a hall-effect sensor, or perhaps it's optical. Are there 4 wires coming back from the postion detector? If it's optical it could be dirty. I'm not sure what the failures of a hall effect sensor would be. If you have access to wires coming back from the sensor, and there are multiple sensors you can try to compare the output of them.

You will most likely have to tear it all the way down and repair/replace the pickup. On pinball machines there are lots of issues with hall effect sensors and optical sensors that are mounted to PCBs... the solder joints break on the little PCBs and the sensors fail.

Not much of help, sorry.

(Ethan O'Toole)
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Anders Haggblom

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Re: Movinghead repair problem
« Reply #2 on: October 12, 2005, 04:55:17 pm »

Quote:

Not much of help, sorry.


Any help is good help. Thank you for your time!

Quote:

There may be a hall-effect sensor, or perhaps it's optical. Are there 4 wires coming back from the postion detector? If it's optical it could be dirty. I'm not sure what the failures of a hall effect sensor would be. If you have access to wires coming back from the sensor, and there are multiple sensors you can try to compare the output of them.



It's a halleffect sensor, in fact there are two sensors. As I said in my previous post I changed the small pcb with the two sensors to a PCB from a working unit with no or little difference. So I think the sensor pcb is ok. Its probably the magnets that trigger the sensors (halleffect sensors ARE triggered by magnets, right? I'm just a sound tech...). What I don't understad is why the unit works sometimes and sometimes not. And I really don't want to tear the whole thing apart and replace the mechanic parts if I'm not 100% sure that it will cure the problem.

Thank you once again. More suggestions welcome!

/Anders
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Jordan P.C. O'Neil

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Re: Movinghead repair problem
« Reply #3 on: October 16, 2005, 10:15:55 pm »

Things to note:
A hall sensor can have a very limited range, down to fractions of a millimeter - check that the sensor/magnet mounts aren't bent/deformed/

Hall magnets are often glued on, and a poor choice of glue, combined with the wrong conditions can cause them to fall off. On a thin piece of metal, sometimes there will be a magnet stuck to both sides. (If the magnet has fallen off, you now have a new problem of finding where ##$!!@@ it is stuck inside the lamp  Evil or Very Mad  )

Best of Luck
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Luc Buytaert

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Re: Movinghead repair problem
« Reply #4 on: October 17, 2005, 03:37:04 am »

Most of fixtures like the spica have also optical sensors. It oare 2 optical sensors against each other, with a U-shape. Between the 2 legs of the sensor moves a wheel with gaps in it.

If these sensors are still OK, check then the connectors or cabling.

PS. 5 Star systems doesn't exist anymore !

Best regards,

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Anders Haggblom

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Re: Movinghead repair problem
« Reply #5 on: October 17, 2005, 05:25:59 am »

Thank you for your replies!


Jordan:
I'll try and play around a bit with the sensors. I think that this might indeed be the problem.

Lucken:
I don't think it has anything to do with the gapped wheel. As far as I can understand, the wheel keeps track of the relative position and the halleffect sensors give the endposition.


/Anders
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Anders Haggblom

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Re: Movinghead repair problem
« Reply #6 on: October 18, 2005, 07:05:12 am »

I think I have solved it now! Since there are two hallsensors there should be two magnets also. There was only one. I found the other one (was stuck under the gear wheel) and glued it in place. The unit works now. I just need to test it a couple of hours before I send it back to the customer.

Thanks all for your help!

/Anders
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