You posted to the Super8 Newsgroup:
>I found a perfectly new Elmo SC-18 sound projector; the one with the built-in "TV screen." The belts were completely loose, so I purchased and installed new belts from Elmo. Still, the projector runs precisely 5% slower, which is quite noticable in speech.

---> Congratulations on your acquisition of a really neat Elmo projector. This one can be pretty handy to have, especially if you 'build' your soundtracks using a projector.

>Any idea what I could do to correct the speed problem? Thanks in advance for any help!

---> If you remove the rear cover of the projector and look near the rear of the circuit board....you'll see a couple fuses, possibly up to three of them. By very close examination of the circuit board, you'll notice two potentiometers used for fine tuning the speed adjustment....and they'll be marked in extremely fine print, 24fps and 18fps. Since it is very easy to make a mistake at this point, carefully score or mark in some way the exact position of the 18fps 'pot'. Then, by using a plastic small flathead screw driver (available from Radio Shack or other electronic supply houses made for this purpose) tweak the adjustment clockwise to increase the speed, or counter-clockwise to decrease the speed.

---> You may want to make up your own timing loop from some scrap film. Cut a length of Super 8mm film that's about 3 to 4 ft in length, long enough to loop it thru the projector and then splice it together. Or alternatively, make your loop, then open the projector's film path and carefully 'install' your timing device (much more difficult). Anyhow, on this film loop, you will have marked off with two different magic marker colors the start and end points for an 18 frame length of film section. Or you can just completely color one section of 18 frames with one color, leave a section of 18 frames clear, and then color the next section of 18 frames etc. Whichever way you decide to do this....select the method and technique easiest for you to do.

---> Now, by using a stop watch or similar timing device.......be prepared to start and stop your timing device. Run the projector and your timing loop, and then start your watch the moment a timing segment shows on the screen and stop it the moment it ends. This is easier than it sounds....and with a little practice, you'll get the hang of it. By observing your watch or timer, you'll be able to tell approximately how far off the speed is. Set the speed upward in tiny increments, run a timing test, and check your results. When you are satisfied that you're correct, project a sound test film to see if you are pleased with the results. If it still sounds fast or slow to you.....you could 'fine tune' this by ear, by it is easy to get way off the mark here....so be careful. The entire procedure should take you about an hour to complete or so. There are other similar methods, and perhaps other readers of this newsgroup will share their ideas and/or methods for a low cost home use remedy of the speed adjustment.

>BTW: Why does Elmo use these thin belts, whereas Chinon uses one metal spring belt and another short and thick rubber belt that seem to hold forever?

---> Each projector company varied what they used in drive belts over the years of production. Elmo's reason for this is that their projectors ran quieter and smoother. This one a main reason most projector manufacturers switched to rubber drive belts from metal. Years ago when the early silent 8mm and 16mm projectors were made, metal was the standard and most had some form of metal sprung belts.....noise was not an issue...since the motors and fans often sounded like vacuum cleaners anyhow! Eumig had a novel idea with their beltless design using a rubber coated driven plate and changing the speed via the position of the drive shaft/ball on the driven plate's radii out from the center. It's like any product.....each company offered something that another didn't have that was often superior in some way.....too bad....they couldn't standardize...but then, neither do the car manufacturers. Moral to the story: stock up on extra belts and any other wear parts if possible to cover all projectors you use regularily.

Best wishes,
Martin
See Martin's WWW site at: Plattsburgh Photographic Services

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