8mm Forum: Eumig S710D Sound - Does the flywheel have to be spinning to get sound??

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Posted by Chad Gayle (Member # 3602) on March 22, 2013, 08:17 PM:

I posted to the forum a few days ago about my problem with trying to get sound out of my S-710D. With the volume turned all the way down, there was silence; with it turned all the way up, nothing but hum. I did everything conceivable except for changing out the capacitors or replacing the sound circuit, with no change.

Tonight, I took the back off and rigged up a connection between the DIN output jack and my guitar amp. At first, all I got was the same hum; then, after I put the projector in reverse with the lamp on, I began to notice some garbled sounds (voices) coming from the amp.

I had taken the back of the projector off to verify that the projector's speaker or its leads weren't causing a problem -- and when I looked at the naked back of the unit, I noticed that the large metal disc that faces the back side, and which isn't connected to anything except a spindle in the center of the machine, was moving.

When the disc (is this the flywheel??) stopped moving, I had nothing but hum again.

So does this disc have to turn for the sound head to pick up the track? And what makes it spin? It doesn't seem to be connected to anything.

* Addendum: I just took another look. With the projector running in forward, the large disc does spin -- but slowly. When I reversed it, the disc stopped spinning.

I think what I've got is a bad sound head.

Posted by Matt McBride (Member # 3311) on March 22, 2013, 09:06 PM:

Hi Chad, so first off the soundhead flywheel is necessary to keep the film going at a constant rate when it passes the soundhead. This is required otherwise you can get wow and flutter in the sound. Also, if you have a projector with the intermittent movement, you'll also notice that sprocket has a flywheel as well. Again this is to regulate the film through the intermittent movement. It basically keeps the "fluctuation" from the electricity "stable". Like you said in the addendum, you probably have a bad soundhead.

Posted by Zechariah Sporre (Member # 2358) on March 22, 2013, 10:20 PM:

I'm going way out on a limb here with no knowledge at all. But is it at all possible that something is broken where the film passes through the sound head and it isn't holding the film against the head. I once had a Eumig that was letting the film go through loosly and it has sound but it was gargley.

Posted by Matt McBride (Member # 3311) on March 22, 2013, 11:28 PM:

You are correct Zechariah. I am not familiar with this particular model, however at least with "modern day" 35mm films projectors, the soundhead has a little dashpot (damper) to help keep constant tension on the film when it passes through the soundhead. I believe the model of the 16mm eiki I have has this as well. If not there should be some kind of tensioning device that holds the film as it passes through the soundhead. So it is quite possible this could result in the gargley sound.

Posted by Chad Gayle (Member # 3602) on March 23, 2013, 03:08 PM:

You guys have hit it on the money. Do you think it's worth trying to get a new sound head?

I already have 2 silent Super8 projectors, so I figure I could sell this S-702D as is (as a silent one) and recoup part of what I paid.

Bummer!

Posted by Matt McBride (Member # 3311) on March 24, 2013, 09:42 AM:

As far as getting a new soundhead, it will almost certainly have to come from another projector out there, unless you post in the wanted section and someone has a spare lying around somewhere. Though with this crowd it quite possible. I just replaced my 35mm projector and I got three so I could have spare parts down the road lol. You could resell, as long as you make it absolutely clear that the soundhead doesn't work right. It will all come down to what you want to do with it.

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