8mm Forum: Sound Troubles

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Posted by Randy Murphy (Member # 6795) on January 21, 2019, 04:36 PM:

Hi All,

hoping to leverage some knowledge from the group. I have two projectors that have sound issues and I am hoping there are easy fixes to them. Both projectors are in great condition except for the sound problems.

THE PROJECTORS
First, there is a Sankyo Sound 762. The problem is that the sound is sped up just beyond it's normal pitch. Not "chipmunk " but still noticeable high than it should be.
https://youtu.be/jQsAbkDk7QM

Second, a Fujiscope Sound SH9. The opposite problem. Sound is slower, regardless of the Fine Adjust.
https://youtu.be/Lod6LeEqohs

Any help would be greatly appreciated. As I say, other than this these projectors are both in great condition.

Hope it is okay to post the youtube links. I just wanted to convey the sound issue accuratley.

Posted by Steve Klare (Member # 12) on January 21, 2019, 04:54 PM:

Hi Randy,

These are probably more a film speed problem than an audio issue. If you can adjust the frame rate you should be okay.

Posted by Lee Mannering (Member # 728) on January 21, 2019, 05:01 PM:

She could need a new motor drive belt

SanKyo will probably be the small metal pot/preset needing minor adjustment in the back. It's usually a small circuit board with 2 presets on. In the 80s my brand new 800 was incorrectly set.

If you are new to this take your time. 😎

Posted by Randy Murphy (Member # 6795) on January 21, 2019, 05:35 PM:

Thank you both. I can take a look at the pot on the Sankyo (thanks for that) but Steve, when you talk about the film speed are speaking of the frame rate (18 vs 24)?

Posted by Janice Glesser (Member # 2758) on January 21, 2019, 05:50 PM:

This is what the speed pots look like on the Sankyo 600. Take the back off your machines and see if you can find them. One will be for 18fps and the other for 24fps. Use a non-metallic object to turn the pots to adjust the speed.

Posted by Steve Klare (Member # 12) on January 21, 2019, 09:23 PM:

The film speed and the frame rate are directly proportional: so and so many millimeters per frame times so and so many frames per second. The trick is adjusting the millimeters per second to be enough so either 24 or 18 frames sneaks past the gate every second.

The ear is pretty forgiving up to about 5% of the correct speed. Outside that tolerance it starts to sound too high or too low in pitch.

Posted by Randy Murphy (Member # 6795) on January 22, 2019, 09:14 AM:

Thank you Janice and Steve. Most appreciated

Posted by Mike Spice (Member # 5957) on January 22, 2019, 09:58 AM:

Just a heads up for those who may not have the electrical safety knowledge.

If you, or anyone else, decides to go poking around inside a projector, even if it is unplugged for a week, the capacitors are still capable of giving you a proper electric shock if you happen to catch the wrong bit while touching another bit of metal, so be careful folks.

The capacitor is the big grey thing in the photo. They come in different shapes and sizes, some are capable of storing several hundred volts for quite a long time after power off.

Posted by Mathew James (Member # 4581) on January 24, 2019, 03:39 PM:

Mike, thanx for posting that! I was thinking the same thing.

Hi Randy. Thanx for the PM. There are not too many enthusiasts in this particular area that i am aware of, but glad to hear someone is closeby. I'd like to tinker in 16mm one day as well. These machines are similar in their maintenance needs...

I am not so familiar with these 2 machines as i like elmo machines mostly, but sankyo is a chinon based machine i believe, and the fujiscope is a good projector as well.

As mike says, just be extremely careful around the capacitors! I don't normally just freely poke around in any electronics anyways, but just be careful if you decide to try anything. Go slow, people here will help!

You should strongly think about replacing the belts in both machines if they have been sitting for a long while. They will stretch, crack, turn to black goo in some cases etc...
Van eck has what you need for these machines, or you can search ebay for the belt(s)

1. Sankyo 762 sound. There is a manual to the sankyo 800 on this forum here in case you want to look at it, must be very similar:
http://www.film-tech.com/warehouse/wareview.php?id=1756&category=2
Since the sound is fast on this one, i don't suspect the belt as much as the pots as janice shows and mentions. My experience is that belts cause slow speed rather, but i could be wrong and i would get new belts regardless. In the meanwhile you can try to find the potentiometers as janice shows a pic of and slowly adjust to back the speed off the 24 fps side.
Here is a link to sankyo 700 parts. i would ask van eck if they might be same belts for 762: https://van-eck.net/itable.php?lang=en&size=0&cat=film&merk=148&type=Sound%20700

2. Fujiscope SH9:
*funny how you got such diametrically opposed sound problems on these two machines [Smile]

You can order parts here: https://van-eck.net/itable.php?lang=en&size=0&cat=film&merk=61&type=Fujiascope%20SH9

On this machine there is a fine speed adjustment, but i think you mentioned you tried that already? if not, i would try to find that adjustment and alter...if you have, then belts next...
Welcome to the fun!

Posted by Robert Statzer (Member # 6708) on January 24, 2019, 04:07 PM:

I picked up an Elmo 1200 a few years back that had an issue with the film speed. It ran just a bit too fast; not enough that you could visibly detect it, but enough that it threw the sound off. Steve Osborne was able to tweak it, and it was as good as new.

Posted by Rob Young. (Member # 131) on January 25, 2019, 11:43 AM:

Quote:

"The ear is pretty forgiving up to about 5% of the correct speed. Outside that tolerance it starts to sound too high or too low in pitch."

Interesting Steve.

Can you explain more?

Posted by Steve Klare (Member # 12) on January 25, 2019, 01:03 PM:

It's actually a rule of thumb I learned from an old friend who was an audio engineer. What it means is in an audio presentation most people will perceive a difference in pitch from the true one within 5% as still being correct, as long as the difference is constant. (Rapid variations within the same program: no!)

It makes sense: All engineered systems have variability. It's something you can only minimize, never eliminate.

-the question is how much is too much.

Posted by Rob Young. (Member # 131) on January 25, 2019, 02:10 PM:

Posted by Steve Klare (Member # 12) on January 25, 2019, 02:28 PM:

Not random: constant.

-You start ramping the speed up and down, they'll be on you in a heartbeat even a lot tighter than 5%.

Within this limit people will tolerate the difference from exact speed. I'm not even talking ideal: just close enough. Not professional quality either, just good enough for Bugs Bunny in the living room.

Try to think about it like this: you have a typical Super-8 projector. You have this speed regulator tuned very often with a single turn pot without any kind of precision reference or speed measurement to adjust by. The mechanisms have a lot of lag: you twist the pot until the speed is what you want, you stop twisting but it keeps changing. How close do you think we are getting tuning these things in by ear? If I could hit 1% flying blind like this I'd be pretty proud!

If we have to get it dead nuts to be acceptable we are in trouble.

I find among my own machines, each one can sound fine on its own, but then I start running several in changeovers the difference in speed becomes obvious right at the change, yet a minute or two later it sounds fine again. It's the change that causes the red flag.

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