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GS1200 sideways judder

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  • GS1200 sideways judder

    I wonder if anyone else has seem the problem I am with the non Xenon GS1200 I have? Some films when run exhibit at intervals a rapid side to side judder in the projected image. The same film run on my Xenon GS1200 does not exhibit the problem.

    The gate area is clean. The side pressure pads are clean and free to move and do rest against the edge of the film correctly.

    I had wondered if some dirt had got in and was holidng those pads away fom the film, but have found that isn't the case.
    Any advice much appreciated.

  • #2
    Hi Clive. I believe what is happening here is that the claw on your standard GS is just catching the edge of the sprocket holes on certain prints. This is because the fixed guides that align the sprocket hole edge of the film in the gate are probably set slightly differently to the guides on your Xenon (possibly even a micro millimetre difference).

    Some prints don't quite meet the tolerance of 8mm and some projector gates are more forgiving than others. Also, possibly someone has fiddled with gate alignment in the past.

    This can be adjusted by yourself BUT it is a precision job which really should be done with the right alignment tools and, ideally, a qualified person.


    • #3
      Just a thought, but try getting some cotton buds right into the 4 gate guides, the fixed and flexible on both sides of the gate, just to make sure that they are both immaculately clean.


      • #4
        Hi Rob - thanks for following up on my post. We are thinking the same - I did use some cotton buds soaked in alcohol and cleared both the fixed and movable guides. I did wonder if it was the claw catching on the sprocket holes.

        I am guessing alignment tools for these machines will be impossible to get now. Can it be done without do you know?
        Last edited by Clive Carmock; December 04, 2021, 01:18 PM. Reason: Clive Carmock


        • #5
          Also consider dryness of the film edges. I have had this with 16mm and the solution was putting the film on a split reel to wipe FilmGuard on a cloth on the sides of the film. With super 8 treat between the spokes to get to the edges. Might help. Try it before taking the machine apart I would.


          • #6
            I have five GS1200´s in use. All restored and new adjusted in Calw and Filmway Area by myself.
            I also have a few Prints who has this side by side moving. But most it is only one or two Reels of a full length feature.
            So I think if the Knife from the splittig Process was worn out, the Film edge on the Sprocket hole side is not in order and the Film begin to move.
            If you have a GS 1200 where the side Guides are worn from the film edge it can be that the Film has not enough pressure from the movable side guide and this failure doesn´t came up on this machine. Another Reason is a worn Calw Tip. This can make an unstable Picture too.

            Take a look into the Elmo GS 1200 Service Manual. There are Pictures of worn Side Guides and Calw Tips.

            This machines are 35 to 40 Years old now. They had a lot of running in the Prime Time of Super 8 Home Movies so today every GS 1200 need a refreshing for a second life.


            • #7
              Here is the service manual of the GS-1200 for anyone interested:-
              GS1200SERVICE.pdf (


              • #8
                Thank you Maurice!
                On the Sides 19-23 you can see the worn Parts.


                • #9
                  Thank you for this - really useful. I'll try to get some good pictures of the claw tip and pressure pads to see if they look to be worn


                  • #10
                    Steven makes a very good point. I've had prints that exhibit this side to side vibration on my Elmo ST but not at all on my Beaulieu. A clean with Filmguard does indeed help with some prints.


                    • #11
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                      I have attached two pictures, one was intending to show the claw condition, but it doesn't really do that well. I don't feel a ridge in the underside of the claw though.

                      When loading a pice of white leader into the gate The lower claw appears perfectly centred, but the upper claw slightly to one side. From looking at the service manual this is not unexpected. Judging from these pictures I'd say the claw position looks reasonably good.

                      Last edited by Clive Carmock; December 05, 2021, 10:26 AM.


                      • #12
                        And be reminded to account for film shrinkage as well. After some 20-30 odd years its acetate base would probably had shrunken down somewhat. Not to the unprojectable point, but just enough to start causing some issues in certain projectors.


                        • #13
                          Yes and then at that point it's time to use the sledgehammer on it .


                          • #14
                            Clive, yes that claw looks pretty well aligned. But if the problem prints run ok in your other machine, then something must be amiss. This is where you really need a qualified engineer to make finite adjustments. Sadly, there aren't many left unless someone has a recommendation.

                            I wonder how many prints are causing you a problem with the one machine?

                            I would still try cleaning them with Filmguard as this can often perform miracles!!


                            • #15
                              Thanks Rob - I'd say about 30% of prints I run on this one have sideways judder. I will certainly try filmguard as I have a couple of bottles of that here.
                              I wonder if the spring tension is too weak on the pressure plate opposite the sprockets