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Author
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Topic: GS1200 Auto Threader
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted February 21, 2015 11:36 AM
Is the auto threading release on your GS1200 acting slow, or occasionally not working at all? In other words does the top auto threading guide stay stuck down even when the film has threaded all the way through to the take up reel? This is a very common , and recurring , problem on the GS, and in 99 out of 100 cases the cause is the failure of the front and/or the back microswitches. Both these switches have to be working in order for the auto threader to release when the film pulls on the swinging film roller at the back of the machine.
My GS threader has been acting up lately, staying stuck down momentarily, or requiring repeated tugs on the film coming out the back of the machine, to finally get the top guide to pop up. Yesterday it stayed down for good, multiple yanks on the film and repeated power ups just would not release it. So yet again, it was time to replace the microswitch. Usually it’s the front one, so I took the back cover off, removed the flywheel, pulled off the helical gears, and removed the switch. Checked it with a meter and it was fine, making contact every time. But passed experience has taught me that this means nothing, something happens to these switches over time, and even though they still make contact, they just will not carry sufficient current to activate the release solenoid. So I replaced the front switch, put everything back, powered up the projector, and lo and behold, it still would not release! ![[Eek!]](eek.gif)
So now it was time to replace the back one as well. Off comes the green film guide and power supply cover, and then the power supply itself. Unsoldered and replaced the back switch. Once again the back switch looked fine when tested with a multimeter. I reassembled the power supply and replaced the power supply cover. Powered up the projector, and this time, the release mechanism activates promply every time, with a reassuring thunk. Its now good for another couple of years! ![[Big Grin]](biggrin.gif)
Having done this now so many times on the GS I have concluded that the peak current going through these switches must greatly exceed their design capability of 5 amps, and the contacts inside the switch sustain some kind of arcing damage every time they close and activate the solenoid. In other words, this switch was a bad choice by the Elmo engineers.
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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 Browning
Phenomenal Film Handler
Posts: 1006
From: West Midlands United Kingdom
Registered: Aug 2011
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posted February 21, 2015 01:19 PM
I get your point Terry, and its the subject of much discussion on this forum, but there's plenty of people who on here know how to fix them, so these little problems would not phase me, its all part of owning these high end machines. There are plenty of problems with other machines, that come up time and again, it doesn't put people off buying them, or recommending them to others, much that goes wrong are wear parts, like with your car that's 30+ years old. I just see them as the plugs, batteries oil and filters.
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted February 22, 2015 11:40 AM
It's hard to beat a GS1200 in top working order. Certainly for public shows outside of the home it is the only projector I own that will do the job, as its level of screen brightness is so much higher than all my other machines. But for home use, I much prefer the 938, and I would use it all the time if I did not have to worry about head wear. I still think if Eumig had designed a 1200 ft machine with 200 watt ESC lighting, based on using the 938 film path and stereo electronics, they would have had a better projector than the GS.
I think ELMO kind of went overboard in the GS design. They tried to make it the ultimate super 8 machine, and as a result they built in many unnecessary complexities. Chief among them is the piano switch controls, with their associated switches, solenoids, relays, and logic circuits - all to avoid someone turning a knob! Then you have the undersized capstan and pinch roller which does not grab the film as it should, so you can get wow on some films, and if you stop the projector and start up again the sound will warble like a canary for a couple of seconds. To reduce this problem, Elmo decided to spin up the flywheel in the standby mode, by gearing it to the fan motor. But even that does not work that great, there's still WOW on start up, which is totally unnacceptable for sound editing on the machine. Eumig had none of this complexity, they just designed the sound capstan and roller to be large enough, and the pinch roller pressure to be high enough, to do the job. My Eumigs give instant wow free sound on start up. And then you have the auto thread microswitch problem, and the film scratch issues, and you see that you have a projector that requires considerable attention to keep it in top working order. My 938, in comparison, thrives on total neglect! ![[Smile]](smile.gif)
When you buy a GS this is what you accept comes with it, and if you like tinkering around projectors, then it can actually be part of the fun. ![[Roll Eyes]](rolleyes.gif) But its certainly not a projector for everyone.
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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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