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Topic: Sound Problem in Prints (WOW)
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Paul Adsett
Film God
Posts: 5003
From: USA
Registered: Jun 2003
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posted November 03, 2005 05:24 PM
I think Jan has hit the nail on the head- it's all to do with the smoothness of the take-up. One of my GS1200'S has a wow problem on many of the films I put thru it. You can see the black plastic tension bar (between the sound head capstan roller and the bottom sprocket)flapping up and down, but if you grab hold of the take up spool, thus releasing the tension from the take up spool, all WOW disappears, and the black plastic flapper is totally stabilized. I agree with Jan that this is an inherent weakness of all the Elmo's. None of the Eumig's , 800 or 900 series, exhibit any wow at all, no matter what the tension on the take up spool.
So how do you smooth out the take up tension on the GS1200 so that it does not jerk on the bottom sprocket?
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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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Rob Young.
Phenomenal Film Handler
Posts: 1633
From: Cheshire, U.K.
Registered: Dec 2003
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posted November 04, 2005 05:15 AM
Now this a strange one.
I bought my ST1200HD back in 1987 and it ran every print flawlessly (with the exception of one particular trailer I remember which was VERY over width). I had a couple of features from Derann (on Kodak), and these were perfect too.
In the early 90's I hired a few features from Derann over the summer and all seemed well except the last reel of "Poltergeist" which went crazy, with the two jockey rollers flailing up and down and the sound wowing like mad! Since it was only hired I lived with it and thought nothing more of it, but interestingly this was probably one of the first prints I ran which was on Agfa stock.
About the same time I bought the last reel of "Romancing the Stone" (on Agfa) and this did the same (Jan, I hadn't altered the take-up spool or tension at all). Since this was my print and I could mess about with it, I discovered that physically holding the two moving jockey rollers in place (whilst allowing them to rotate) stopped the wow. Now obviously there were some tension changes going on somewhere in the film path which would have to be absorbed elsewhere, so this was a bit naughty and could have potentially damage the print.
I stuck a scrap film loop on the projector and let it run all day with the jockey rollers locked in place. Then I examined it with a magnifying glass for any wear, especially strained sprocket holes, and found none. So when I ran this reel, I devised a way of locking the jockey rollers in place. It got me through showing the print wow-free many, many times without any excess wear (although heaven forbid I am suggesting anyone else try this! Do so at your own risk, I'm just saying it worked for me!!!)
Through the 90's I bought lots of new features and all ran perfectly until suddenly I bought one where all four 600ft reels wowed like mad. It was the same thing, the two jockey rollers moving around like crazy. I hadn't changed the take-up spool or altered anything and every other print still ran ok.
The very generous supplier ( ![[Wink]](wink.gif) ) offered to change the print, but the next one was the same. It was suggested that this may be the "twin" to the original print and that they would change it again for a print from the next new batch.
The next print ran perfectly ![[Confused]](confused.gif)
About the same time I bought lots of new trailers and one of them behaved in the same way, wowing like mad. No amount of Thermofilm seemed to help so I just lived with it.
A couple of months later I bought another feature (this was in the late 90's) and the same problem arose. A bit embarrased at the thought of ringing the supplier again (lets face it they had already been more than generous) I kept the print and decided to live with it.
I tried everything. Thermofilm didn't help, and locking the jocky rollers down this time didn't help either. You could see the lower film loop actually changing in size as the print refused to run uniformly across the capstan.
I sought lots of advice and one interesting point which came up was that if the print had too much lubricant on it (or the lubricant was not uniform) the print could slip when passing through the capstan, pressure roller assembly and then get "snatched" as grip was found again, creating wow. This it seemed was a well known issue on Elmos, especially with the brass capstan roller.
Cleaning off the Thermofilm didn't help and eventually I boxed the print up and stuck it in a drawer. Well, a few months later I had another go and amazingly the print ran perfectly!!!
Since then, if I have encountered this problem (and I have to say very rarely) I just leave the print for a few weeks and it usually resolves itself. I'm talking about polyester prints here. I don't claim to understand what is going on. I can only guess that it is because the prints are lab new and over time something changes. Perhaps the film base is not a consistent thickness after processing and this settles down as the print dries and ages slightly? Just as an after thought, as has been said already, you do have to make very sure the wow is being caused by the print not running smoothly and isn't actually in the recording itself as is sometimes the case ("Raiders", John he he).
Touch wood the newer Kodak stock prints don't seem to exhibit this.
I'd love some more suggestions on this.
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UBBFriend: Email this page to someone!
![[Roll Eyes]](rolleyes.gif)
one idea I've had is to use some kind of braking pad on the lower sprocket... sort of give it some resistance so it turns at a more constant speed without the take-up pulling force causing it to jerk around (especially at the beginning of a movie, when take-up pull is the strongest)... So far I've only thought it through in theory, though. (Wow, I think I just came up with a tongue twister here!!)![[Big Grin]](biggrin.gif)
![[Smile]](smile.gif)
![[Cool]](cool.gif)
I think I got the whole thing licked on my end, but should I run into trouble again, I might try fixing one of the rollers in place and just letting the other one do its job. Sort of a compromise between the way it's supposed to work and the way Rob dealt with it that one time.![[Mad]](mad.gif)
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