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Topic: Noisy Cat. 701

David Whitbeck
Film Handler

Posts: 70
From: Tempe, AZ
Registered: Jun 2001

posted 05-11-2002 06:52 PM

We have 2 Dolby Cat. 701 soundheads and both of them are quite noisy. One is about 3 years old while the other is brand new. Both make a lot of noise on the sprocket. It's mostly with newer prints but it lasts for the entire run with some of them. It sounds like the sprocket is nicking the sides of the sprocket holes on the film as it passes over the sprocket. Is this normal or not? Is my tension wrong? I usually have the tension pads on it about half an inch apart.

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 05-11-2002 07:00 PM

You are misthreading them. Go one sprocket lower. There is a tension guideline in the form of a white "half moon". Basically, you want the two rollers about as far apart as to barely be able to insert a pencil in there. Dolby penthouses do not suffer from this, although it is standard with SDDS.

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David Whitbeck
Film Handler

Posts: 70
From: Tempe, AZ
Registered: Jun 2001

posted 05-11-2002 07:22 PM

So I just want a pencil to be able to go in between the two tension rollers and touch both of them and maybe barely push on them?

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 05-11-2002 07:49 PM

I always put up with the noise and favor slightly high tension on the Davis loop as it can damp out better

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 05-11-2002 10:56 PM

Do check to be sure you are threading them correctly. Look for the half circle like Brad said. If you like them tight you can go for one sprocket hole tighter.

However... Do be sure there isn't too much back tension from your platter. Is the brain and the payout roller path correctly threaded? And, are all your rollers spinning properly?

I like them to be as silent as they can be because, when I was in the booth, I used to use that noise as a telltale for when one of the new guys was doing it right. I could walk down the row and suddenly walk up to the other guy and say, "Go check number 9. You have a misthread!"

On more than one occasion I was able to avoid any serious damage due to a brain wrap. I would be standing there when I heard, "buuuUUUZZZZZ!!!" I dove for the stop button just in time to save the film.

When you do things like that DO NOT explain these tricks to just anybody... How are you supposed to get the reputation as a miracle worker if everybody knows your secrets?

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David Whitbeck
Film Handler

Posts: 70
From: Tempe, AZ
Registered: Jun 2001

posted 05-11-2002 11:56 PM

Yeah, I had that same thing once, but I didn't stop the movie, I just fixed it while it was running... Stupid middle roller on the Christie brain came loose and the film popped out of it. Was able to get it fixed though and nobody was the smarter, we were interlocking so I wasn't planning on stopping it, it was our first time doing that. Pretty entertaining that's for sure. I don't really see what you're saying with the half circle thing, but I'll figure it out I'm sure. Everything else is laced properly so I'm pretty sure I'm just giving it too much tension. I did slack off to the gap being a little more than the size of a pencil cause any less and the rollers were almost touching. It seems to have quieted down so hopefully that took care of it.

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 05-12-2002 03:11 PM

Take a look right behind the bar that the pad roller attaches to. It's on the "bulkhead" right behind that bar. It's a little white half-circle, oh, about a 1/2 inch in diameter. The top edge of the bar is supposed to line up with the bottom edge of that circle when the tension is correct. There's one on the bottom as well.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 05-12-2002 06:34 PM

On the 700 with the top pad roller open the damper arms are locked and the best I have found is to pull just enough to lift the top damper then close the pad.
This was the way the old Simplex XL mag penthouse worked as well

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Jacob Huber
Expert Film Handler

Posts: 172
From: Evansville, IN, USA
Registered: Feb 2002

posted 05-12-2002 09:12 PM

I had this exact same problem because one of the guys who I was "training" with told me the tension rollers could be as far apart as was possible, but should never touch. I was walking by one of the proj. with the cat. 701 on it and it was making the worst noise. I talked to the tech about it, and pointed out in the manual they should be about .25-.50 inches apart. I thread them so when I try and stick my pinky in between, they have to expand just a tad. No problems or noise since.

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