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Topic: Optical Sound on the GS1200
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Hugh Thompson Scott
Film God
Posts: 3063
From: Gt. Clifton,Cumbria,England
Registered: Jan 2012
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posted June 02, 2013 10:06 PM
The plastic film guide does wear, as the film cuts into the side,a repair can be done with epoxy resin or replacement,if you have a spare. I replaced this part many times on the ST1200.i wouldn't do any re adjusting just yet, as these lenses & receptors are factory set, and once moved,getting that little light slit re alighned is a devil of a job.The problem with the guide wearing ,is that it isn't good news for the soundtrack either,being liable for scratching. In desperation with this part, I once filed out the offendind side and fitted a little piece of aluminium,held with Araldite that did the trick for a while,being tougher than the plastic.
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted June 03, 2013 02:04 PM
Hi Mauritzio, You hit the nail on the head. It is definately a problem of not enough pressure on the rubber roller. When I push on the green arm at the roller, the loop of film between the roller and the bottom sprocket stabilizes against the black tension arm. When I do not push on the roller, the bottom loop size oscillates up and down, with the sound level also going up and down in phase with the loop size. I have tried re-adjusting the green arm position anticlockwise, but it did not help. I went to page 47 and 48 of the service manual and they say to adjust the arm pressure by moving the solenoid position (2). Have you ever done this?
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted June 04, 2013 04:54 AM
The green arm on my GS1200 already has the metal shaft insert. IMO this situation confirms what I have long suspected, namely that Elmo projectors are sometimes prone to film slippage at the sound capstan, due to insufficient roller diameter or insufficient pressure, or a combination of both. I have heard WOW on some of my magnetic sound films on my GS1200'S which I never hear on any of my Eumig's. Eumig's are totally WOW free. Elmo's can sometimes exhibit detectable WOW with some particular films. Its not every film by any means, but it happens often enough to show that the Elmo is sometimes touchy in regard to the physical properties of the film, how slippery a particular film may be, or how much flexibility it may have. When you switch to optical sound on the GS1200 the situation apparently gets even more touchy because, as Mauritzio has pointed out, you no longer have the magnetic sound pressure pads clamping the film, resulting in my case to wild swings of the film loop size between the sound capstan and the lower sprocket, which also oscillates the distance of the optical track from the sound sensor. Since I have only a couple of optical shorts I probably won't persue this issue any further. Magnetic sound is fine almost 100% of the time. I am reluctant to mess around with that solenoid position, who knows what else may get screwed up.
-------------------- The best of all worlds- 8mm, super 8mm, 9.5mm, and HD Digital Projection, Elmo GS1200 f1.0 2-blade Eumig S938 Stereo f1.0 Ektar Panasonic PT-AE4000U digital pj
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