8mm Forum: GS1200 Crackling when running Optical films

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Topic: GS1200 Crackling when running Optical films

Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 08, 2007 03:35 PM

Having now seen a picture of Ugo's GS1200 Xenon in my other thread about the cracked fan in my machine some of you might have read that I have the version of the GS1200 Xenon that has the extra transformer to boost the voltage to the fan motor.

This also has the effect that the earthing 'spring' is not present on the flywheel and I wonder if this causes the problem I have experienced.....

When I run an Optical soundtrack film after a while of running I get the odd crackle and pop int he sound track. I am wondering if this is in some way due to static build up and then discharge causing a spark 'seen' by the photocell. I remember reading that most Optical track 8mm films were on mylar or polyester stock which can exhibit more statis issues than acetate.

I don't get any such issues with magnetic track films, however that doesn'tmean that the static isn't discharging in this way, but that it doesn't affect he magnetic pickup just optical.

This is all just theory, as I have no idea whats causing this at the moment.

I woner if any others with the version of the Xenon machine that doesn't have the earth strap have had the same issue?

Regards

Clive

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted January 09, 2007 01:26 AM

Clive, you are spot on this is ststic and yes will be caused by the lack of earthing.

I have heard this on the ST1200 which doesnt have the earthing strip. You will also find that it's polyester film stock as the static builds up badly with this type of base.

There's not too much you can do about it unless you can find away to earth the centre of the flywheel.

I have heard it on the mag sound too in severe cases of static build up. The reason you hear it on Optical first is I think it arcs over from the back of the capstan onto the optical pickup cell.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Tom Photiou
Film God

Posts: 4837
From: Plymouth U.K
Registered: Dec 2003

posted January 09, 2007 04:53 AM

Definatley true about the polyester stock, on my older 1200ST the marketing films in particular use to crackle someting awful, what would help ease it for me was to run a little film cleaner before viewing, (didnt always work, but it did help reduce it)
[Wink]

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Lee Mannering
Film God

Posts: 3216
From: The Projection Box
Registered: Nov 2006

posted January 09, 2007 06:28 AM

I also found that cleaning the X airline prints helped with this problem, but when the prints were shown on my Fuji SD auto or Eumig MO I had no problems. Bit of a strange one this ....

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Clive Carmock
Film Handler

Posts: 69
From: London, UK
Registered: Feb 2005

posted January 09, 2007 03:17 PM

Yup the prints I have are ex Airline. One of the worst is a Fish Called Wanda which often seems to crackle like mad in sections, and only after it's been running for a while.

Since I have the transformer in the way Elmo clearly left out the earthing strap. I am wondering if I can fit a band of springy metal ilike an upturned U bolted to the chassis going up over the transformer and touching the axle of the flywheel to earth it.

Kev do you suffer from this issue on your GS1200? I assume yours has the earthing strap sicne yours doesn't have that transformer?

Clive

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Osi Osgood
Film God

Posts: 10204
From: Mountian Home, ID.
Registered: Jul 2005

posted January 09, 2007 05:53 PM

Hey Clive, you wanna part with A FIsh Called Wanda?

(hee hee)

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"All these moments will be lost in time, just like ... tears, in the rain. "

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Kevin Faulkner
Film God

Posts: 4071
From: Essex UK
Registered: Jun 2003

posted January 09, 2007 06:13 PM

Clive, The original is U shaped and no I dont get any problems at all. I think because of the way the capstan is mounted in the bearings is what causes the problem of static build up. Probably the grease in the packed bearings gives a bad earth.
A lot of the cheaper machines have very simple bearings and even just brass bushes which the capstan turns in but the Elmo's have ball bearing bushes.

Even the Elmo 16mm machines have this earting to the rear of the capstan so yes if you can devise a method to earth the capstan I'm sure it will help.

Kev.

--------------------
GS1200 Xenon with Elmo 1.0...great combo along with a 16-CL Xenon for that super bright white light.

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Del Phillipson
Jedi Master Film Handler

Posts: 679
From: Derbyshire, England
Registered: Dec 2005

posted January 10, 2007 01:24 PM

I have this a lot with "Over the Top" and "Rising Damp" but it's not as bad after a thorough cleaning but is still there, I always thought it was dirt on the airline prints. But thanks for the info, I'll have a play.

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Brian Hendel
Jedi Master Film Handler

Posts: 902
From: New York, New York
Registered: Jun 2003

posted January 14, 2007 10:48 AM

Last night I started getting severe audio popping on my GS1200. It kind of comes and goes, without ever completely disappearing. It's really annoying. It does sound like it's being caused by some kind of static problem but it's there on every type of film I play. I can mute it a little by putting the treble all the way down but then the sound is muffled. Is there really nothing that can be done to clear it up? Having had my projector back working for only a month I am very frustrated again. [Confused]

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Mike Peckham
Phenomenal Film Handler

Posts: 1461
From: West Sussex, UK.
Registered: Jun 2003

posted January 14, 2007 11:43 AM

Brian

You could try Kevs dirty switch cure, it worked for me: With out a film in the projector, set it running in the play mode, with the record switch slid over to the record position, then flick the record switches up and down a few times.

Apparently they are self cleaning when used but if the machine isn't used for recording they can tarnish and cause interference in the sound.

It happened to mine and sounded like a sort of static, clicking sound with a bit of white noise thrown in for good measure. Of course your problem might be something quite different but it wont do any harm to give it a try.

Good luck

Mike [Smile]

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Auntie Em must have stopped wondering where I am by now...

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Brian Hendel
Jedi Master Film Handler

Posts: 902
From: New York, New York
Registered: Jun 2003

posted January 14, 2007 12:43 PM

Mike - I'm going to try that now. It's something even I can do! I'll let you know if it works...

Brian

OMG It's working! At least for now the sound is normal again. I really think my GS is trying to drive me crazy. After all I've been through, last week the top threader stopped releasing again. After inspection I found that the back roller that releases it had unscrewed and fallen inside the projector. It took ages to fish it out. Then this weekend the crackle and pop sounds started. I think I am ready to try another 1200' stereo projector... any suggestions? I have a tempermental GS that's up for trades!

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