Film-Tech Forum ARCHIVE: RCA Soundhead Noise on sound track

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Posted by Mark Farr-Nash (Member # 4233) on 05-19-2007, 10:47 AM:

Gents,

I just had my projectors serviced, but I'm having a slight problem with one of my RCA soundheads (I think). Just after the splice for reel five goes through, the surround sound channels pick up a scratchy hiss. This goes away when I slightly increase the tension by pressing down the top roller? guide? and then after about thirty seconds, stops altogether. It didn't happen when I screened the print (naturally), but it happened during all of my evening shows last night.

When threading, I'm pulling the film across the soundhead tightly, and then backing off one sprocket, as I was instructed. Is this the correct way to thread? It's either that or the splice, at least, to my noobie way of thinking.

Any help/advice would be appreciated.

Mark Farr-Nash

Posted by Sam D. Chavez (Member # 1841) on 05-19-2007, 11:50 AM:

The idea is to have a little slack on the film after you close the lateral guide roller assembly. If you put your finger on top of the film going over to the top soundhead sprocket it should not be tight.

The lateral guide adjustment may be just a bit off. If you want to try moving this to see if it helps, first mark the nut with a Sharpie pen so you know where you started. You can make very small adjustments (like a 1/10 of a turn in either direction while listening to the sound on the booth monitor preferably with head phones.

Posted by Gordon McLeod (Member # 33) on 05-19-2007, 08:20 PM:

Because it is a split nut on the lateral guide it often shifts a little when one tightens the locking screw
I normaly close the damper and pull tight then back off 2 perfs (simplex sh1000 3 perfs) it was supposed to be 3 but the RCA is sloppy lateral guide and often the film will be too unstable lateraly after a splice

Posted by Bob Koch (Member # 1062) on 05-20-2007, 05:37 PM:

Gordon is right;2 sprocket holes on both of these reproducers. One hole is too tight.

Posted by Mark Farr-Nash (Member # 4233) on 05-23-2007, 01:55 PM:

When I thread the projector, backing off one or two sprocket holes seems to make the problem worse--meaning, the noise starts with the trailers.

I just ran it again, cold, to test it, after cleaning and oiling the machine. No problems whatsoever. But, running it a second time, with the machine all warmed up, that's when the "Schhhhhh" sound starts on certain splices.

I thought it was maybe the film guide on that particular gate, but now I'm thinking that the arm is too loose--sprung, or what-have-you.

Am I way off in my guess? Documenting the behavior of the machine this past weekend, that's what I came up with.

Mark