Jump to content



Photo

BFD and Master Primes issue...


  • Please log in to reply
10 replies to this topic

#1 Richard James Lewis

Richard James Lewis

    Advanced Member

  • Members
  • PipPipPip
  • 397 posts
  • London, UK

Posted 28 September 2008 - 06:20 PM

Hey guys n gals.

So I'm on a job at the moment using a set of Master Primes on the RED.
I have an MK-V FMG 6 and a BFD.
Our widest Master prime is an 18mm, and we have Super Speeds which are wider. Today we had the 18mm on the camera; I was calibrating the BFD on the lens. I started to roll out the wheel, and the motor and the lens started to violently twitch. I initially thought it wasn't getting enough power, but all I had to do to stop it twitching was apply a bit of pressure to the focus ring. Once that was done, the twitching stopped temporarily, that is until you made any move on the lens again, where it would commence rapidly twitching.
We took the motor off the mount on the bars, held it against the lens, and tried to calibrate again, no issues at all. It was just when back on the bars that it started twitching again. We tried mounting the motor at various different angles and the same would happen. We also tried to vary the amount of contact pressure against the lens with the motor.
Eventually after a bit of swearing and some head scratching, we swapped the 18mm for the 12mm Super speed, and everything worked perfectly.
There was a bit more resistance from the Super Speed, a tad stiffer.
The Master Primes are silky smooth and very easy to turn.

As I say, the only way I could stop it from twitching was to apply some pressure to the focus ring as the motor was engaged and doing its thing.

It couldn’t have been a signal interference issue as it worked fine with the Super Speed, also when in calibration mode and with the transmitter off, it would be irrelevant.

I checked that everything was tight on the bars, no movement there at all.
With the motor off the lens rolling out the wheels, the motor was fine, nice and smooth.

I’m stumped on this one, and any insight would be appreciated, especially as I’m back on it in a few hours.

Kind regards.

Rick Lewis.

Edited by Richard J Lewis, 28 September 2008 - 06:26 PM.

  • 0

#2 Gus Trivino

Gus Trivino

    Advanced Member

  • Sustaining Members
  • 236 posts
  • Buenos Aires, Argentina.

Posted 28 September 2008 - 09:06 PM

Hi Richard

Years ago I had the same symptom using BDF and M-One, and the problem was in the Motor cable.
try changed for a backup motor cable if you can.
All the best,

Gus
  • 0

#3 Lukas Franz

Lukas Franz

    Advanced Member

  • Sustaining Members
  • 187 posts
  • Zurich, Switzerland

Posted 29 September 2008 - 02:31 PM

Richard, check the power! If it's too low, errors like you described could happen. Maybe a power loss through cables or receiver!? Just check it.

Good luck.
Lukas
  • 0

#4 Richard James Lewis

Richard James Lewis

    Advanced Member

  • Members
  • PipPipPip
  • 397 posts
  • London, UK

Posted 29 September 2008 - 05:56 PM

Hey guys, cheers for the advice.

Same thing happened again today.

The thing is, it works with the super speeds! So it must be getting enough power, and the cable must be fine...

This is why I'm so stumped. Its just the Master Primes that are causing an issue.

Rick.
  • 0

#5 JimBartell

JimBartell

    Advanced Member

  • Sustaining Members
  • 494 posts
  • Long Beach, CA, USA

Posted 29 September 2008 - 06:24 PM

I've been thinking about this and I may have an answer. I believe the potentiometer in the motor is beginning to develop some drag and the gear on the potentiometer's shaft is slipping because of it. When you apply drag the motor can't accelerate as fast and the gear doesn't break free and start slipping. With the drag gone the transition from stationary to full speed (when switching into calibrate mode) is nearly instantaneous and the potentiometer gear breaks free and begins to spin, casing the motor to run wild.

If I am right the only way to test this is to open the motor up and tighten the gear (if that is even possible). And even if this does fix it the potentiometer is likely to get worse and will eventually fail. I would contact MK-V and have them service the motor.

I hope this helps.

Jim "Gyro Gearloose" Bartell
  • 0

#6 Richard James Lewis

Richard James Lewis

    Advanced Member

  • Members
  • PipPipPip
  • 397 posts
  • London, UK

Posted 30 September 2008 - 02:33 PM

Thanks for the information Jim, as much as I didn't want to hear that it was going to be such a big issue.

Let's hope MK-V can help me sort this out quickly. I shall let you know how I get on.

Many thanks,

Rick.
  • 0

#7 Richard James Lewis

Richard James Lewis

    Advanced Member

  • Members
  • PipPipPip
  • 397 posts
  • London, UK

Posted 02 October 2008 - 12:56 PM

Does anyone know how to take apart an FMG 6 motor?

Jim, thanks again for the insight. Why do you think that if the gear is tightened properly, the potentiometer would eventually fail?

Best,

Rick.
  • 0

#8 JimBartell

JimBartell

    Advanced Member

  • Sustaining Members
  • 494 posts
  • Long Beach, CA, USA

Posted 02 October 2008 - 01:09 PM

Does anyone know how to take apart an FMG 6 motor?

Jim, thanks again for the insight. Why do you think that if the gear is tightened properly, the potentiometer would eventually fail?

Best,

Rick.

All potentiometers will eventually fail, but it is hard to say in this case if it will fail soon or much later. I suspect the pot will be "sticky" and need replacement immediately, but that is just a guess.

Jim "Pot aficionado" Bartell
  • 0

#9 Richard James Lewis

Richard James Lewis

    Advanced Member

  • Members
  • PipPipPip
  • 397 posts
  • London, UK

Posted 03 October 2008 - 03:20 PM

My own electronics engineer has sorted this problem now...

After finally working out how to get the casing apart we found that, as Jim suggested, the potentiometer gear had come loose from the drive gear.
Strange design in there, but at least I know what to do again if anything goes wrong.

If anyone else ever has trouble with an MK-V FMG-6 that is out of warranty, feel free to get in touch with me, and I will see if I can point you in the right direction.

Best,

Rick.



Does anyone know how to take apart an FMG 6 motor?

Jim, thanks again for the insight. Why do you think that if the gear is tightened properly, the potentiometer would eventually fail?

Best,

Rick.

All potentiometers will eventually fail, but it is hard to say in this case if it will fail soon or much later. I suspect the pot will be "sticky" and need replacement immediately, but that is just a guess.

Jim "Pot aficionado" Bartell


  • 0

#10 JimBartell

JimBartell

    Advanced Member

  • Sustaining Members
  • 494 posts
  • Long Beach, CA, USA

Posted 03 October 2008 - 07:19 PM

After finally working out how to get the casing apart we found that, as Jim suggested, the potentiometer gear had come loose from the drive gear.


Boo-yah!

Jim "I rule!!!!!" Bartell
  • 0

#11 Gustavo Penna

Gustavo Penna

    Advanced Member

  • Sustaining Members
  • 61 posts

Posted 24 December 2008 - 01:05 AM

Absolutely the same, happened to me.... the last time happened when i was using the masterprimes, with the RED. the first time it happened it was with cookes. both times turned out to be the potentiometer on my M1. the last time i troubleshoot with everything and it was always the M1, i tried my other M1 & all was Sharp. i just got my M1 back from palomar & want to thank Don for his quick response on the fix.

GAP
  • 0




Omnishot Systems

rebotnix Technologies

Betz Tools for Stabilizers

PLC Electronics Solutions

Varizoom Follow Focus

Paralinx LLC

SkyDreams

Teradek

GPI Pro Systems

Ritter Battery

Media Blackout - Custom Cables and AKS

PLC - Bartech

Engineered Cinema Solutions

IDX

Boland Communications

Wireless Video Systems

BOXX