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NPR Perfectone Motor Problem


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#1 Kevin Powell

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Posted 15 July 2011 - 11:40 AM

About two years ago, I had my perfectone motor rebuilt with variable speed crystal control at Optical Electro House(not the most pleasant folks). Bernie O overhauled my NPR, laserbrightened my gg, and converted to U16(Bernie is awesome). I ran one 400'roll through the camera, processed and transferred it with beautiful results. I then stored the camera. Now I need it for a project and for some reason, when I apply power to my motor, the sync light illuminates and my motor is dead. No response at all. Just sits there with the sync light on and doesn't run. I'm using a brand new 12v 5ah battery and my multimeter says it's outputting proper current. Anyone have an idea what could be wrong? Any help appreciated!

-KP

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#2 John Sprung

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Posted 15 July 2011 - 02:00 PM

I'd hope it's just resistance in the connector and/or the switch. Can you open it up and check the voltage after the switch?



-- J.S.
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#3 Kevin Powell

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Posted 15 July 2011 - 02:25 PM

Hi John, thanks for the reply. That makes sense to check there. I'll pull it apart this evening and see if I can troubleshoot the connector and switch. It seems so weird to me that it was working perfectly before storage, and now isn't working at all. I have two of these motors, the other has never worked though. I have never been able to track down any good info or schematics for these motors... I'm not 100% sure I know whats going on inside there... especially the crystal controller box. Does anyone know if there is special maintenance that I should be doing? Maybe lubrication of the motor/shaft, etc? My first reaction is to be a bit upset after what I paid Optical Electro to add the speed controls and "rebuild" my motor, only to now have a non-reliable paperweight.

-KP
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#4 John Sprung

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Posted 15 July 2011 - 02:38 PM

Maybe lubrication of the motor/shaft, etc?


With the power disconnected, turn the shaft by hand. If it feels OK, I wouldn't mess with it. If it feels gummy or grindy, that's the problem.



-- J.S.
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#5 Kevin Powell

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Posted 15 July 2011 - 05:33 PM

The shaft turns smoothly by hand. I'm hoping it's only a simple connection problem. Seems strange though that the sync light is receiving power but the motor itself isn't. I suppose that means that the problem is after the controller box in the circuit possibly. Besides the complexity of the controller circuit board/box, I imagine the motor itself is as simple as any other 12v motor I've dealt with.
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#6 Kevin Powell

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Posted 16 July 2011 - 07:17 PM

Disassembled the power connector and switch - meter reading was a full12v at the connector and the switch simultaneously. I removed both end caps, applied power, and just wiggled the motor around inside the casing... It fired right up. I'm not sure what I did to make it work... But at least it's worth something other than a paperweight for the moment.
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#7 Ian Cooper

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Posted 17 July 2011 - 03:41 AM

Disassembled the power connector and switch - meter reading was a full12v at the connector and the switch simultaneously. I removed both end caps, applied power, and just wiggled the motor around inside the casing... It fired right up. I'm not sure what I did to make it work... But at least it's worth something other than a paperweight for the moment.


Sounds like good news. Does your motor use the unreliable 'green' connectors, like the ones shown in this thread I started on my motor? In the end I replaced them with a modern alternative (which was a bit of squeeze to get inside the box!). Although I haven't used the camera a great deal since, I haven't experienced the motor problems when I have. If all you've done is wiggle connectors around then it sounds like a similar issue.

The fact the 'sync' light came on whilst the motor wasn't turning isn't too suprising. Whilst I don't know the precise details of your motor, in general closed-loop speed control means the motor will be driven by a PWM (pulse width modulated) voltage. The width of the pulses will determine the motor speed. There will be a speed feedback sensor fastened to the motor which will give an indication of the motor actual speed. The control circuit will compare the speed feedback from the motor to the reference speed generated by a crystal oscillator (or from a user twiddly knob), then adjust the width of the pulses driving the motor until the error difference is reduced to zero. If there is a big difference in speed references then it will apply a large correction to the motor pulses, if there's only a small difference in speed then it will only tweak the motor drive pulses slightly. If the difference is too great then the 'sync' light will be illuminated.

The fact that the motor wasn't turning would mean no speed feedback, so the error difference between actual speed and the crystal reference would be large, so the sync light would be lit up. This would suggest the problem lay on the drive side to the motor - either the connection to the motor, the transistors used to drive the motor, or the circuit generating the pulse train.

If you loose the feedback from the motor then once again the difference signal will be large and the circuit will try to compensate, only what will happen is the motor will run up to maximum speed in a vain attempt to reduce the speed error (or it will stop if it thinks the motor is running too fast, which is an unlikely failure mode). In this case the suspect areas would be the speed sensor on the motor, its connections back to the control circuit, then any electronics which process that signal and compare it to the crystal reference.

If you haven't got the equipment (oscilloscope) to start tracing the signals through the circuit then you'll struggle to do much more than plug wiggle or look out for obviously damaged components. Even with the relevant test gear one will still struggle without a circuit diagram to show exactly how the components are connected. Eclair didn't make life any easier by wiring everything together with great bundles of wires all the same colour!
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#8 Kevin Powell

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Posted 19 July 2011 - 05:08 PM

Hi Ian. Some good info there - thanks for sharing.

No "green" connectors in my motor. Once the controller box is removed from the top of the motor, it's pretty much just a circuit board. I definitely notice that the more I play with the motor...turning it on and letting it run for a bit, increases the response time. If I let it sit overnight and hit the power, it's response isn't as fast to get up to sync speed a if it's warmed up. Again, not sure why.

Anyway, taking it apart and wiggling things around seemed to get it going! I'd love to have a Tobin motor - they seem hard to come by though :(

-KP
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#9 Ian Cooper

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Posted 20 July 2011 - 02:03 AM

...I definitely notice that the more I play with the motor...turning it on and letting it run for a bit, increases the response time. If I let it sit overnight and hit the power, it's response isn't as fast to get up to sync speed a if it's warmed up. Again, not sure why...


Is that with it connected to the camera, or seperate?

If it's connected to the camera it might suggest it could benefit from a clean and re-lubricate? After you've let it run for a bit the greases and oils will have had chance to soften etc, motor warm though (ie. make the lubricant in its bearings soften up as well), so the camera load will be reduced a bit compared to when you start it 'cold'?

I don't know what your motor is like 'normally', my own motor reaches sync pretty much instantly. If 'wiggling' gets yours going then it suggests connector issues, or possibly dry solder joints? Both could give increased impedance on the motor connections and thus perhaps less starting current available to the motor, and therefore reduced starting performance??

Afraid that's somewhat clutching at straws and guessing though.
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#10 Kevin Powell

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Posted 25 July 2011 - 04:44 PM

The issue with coming up to sync speed doesn't appear to be directly realated to when the motor is mounted on the camera, but i'll have to test that more specifically when I get back to my studio tonight. She was all cleaned and lubed up just before I stored it, but that does make sense that over the course of the past year those lubricants may have stiffened up. From what I can see, the solder points all look good, but I suppose it's hard to tell without actually testing each of them properly with current. I'm liking your theory of hardened grease and lubricant... that seems to be a most likely cause. I have been running the motor mounted on the camera with a magazine periodically to see if I can "break-in" the lubricant and all the moving parts a bit more before I have to actually roll film through it. Once she's "warmed up" a bit, it definitely reaches sync speed in half the time... a second or two versus five to ten seconds.

-KP
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#11 dan kessler

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Posted 25 July 2011 - 06:03 PM

Pretty much agree with Ian's troubleshooting sequence,
and the fact that your motor fired up when wiggled
suggests a connection problem rather than bad electronics.

I would look for something loose, broken, brittle, cracked, etc.
in the power wiring to the motor, maybe even inside the motor
itself.
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#12 Ian Cooper

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Posted 26 July 2011 - 05:08 PM

...it definitely reaches sync speed in half the time... a second or two versus five to ten seconds.


Once again, I don't have any personal experience of the Perfectone Motor - I don't know exactly what the motor model on mine is - but five to ten seconds doesn't sound 'normal'. My motor hits sync in less than a second, it's as good as instant.

Afraid I can't think of much else to suggest you could easily try yourself.
Sorry, but best of luck trying to track down the solution.

Ian.
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#13 John Sprung

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Posted 26 July 2011 - 07:02 PM

How about brushes and commutator? Can you get a look at them?



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