Mystery Sound Troubles

[Fruma Elizabeth]

(I apologize if this topic is in the wrong section)

I’ve been having an issue I’m at a loss to explain; I use a Eumig Mark S 810 D Projector, and have two Super 8 sound films. Before a little while ago, both of their soundtracks played back perfectly. But, rather suddenly, they have begun to “waver” for lack of a better word; the sound with suddenly get very quiet, then shoot back up to normal, then quiet again. From what I can tell, the pattern is completely random (i.e., its not a stable up-down-up-down pattern) but doesn’t change each time I run the films. But as the films progress, the effect gradually disappears and the sound plays back normally. I’ve looked inside the projector to see if thats where the problem lies, but due to my inexperience with projector maintenance I didn’t get very far. To me, all signs point to the point to the films themselves being the issue. My best theory is that the stripes somehow got too close to a magnet which erased parts of the sound, but that doesn't explain the intermittent nature of the problem or the fact that it goes away about halfway through the films. I’m wondering if anyone here has some insight?

[Maurice Leakey]

Fruma
It's a long shot, but the volume control may be giving trouble with its contact with the carbon track which alters the volume.
After many years it is a good idea to "lubricate" its movement by turning the volume control fully forwards and backwards perhaps, at least, a dozen times or more.
Try it, it may help.

[Ed Gordon]

... But, rather suddenly, they have begun to “waver” for lack of a better word; the sound with suddenly get very quiet, then shoot back up to normal, then quiet again. From what I can tell, the pattern is completely random (i.e., its not a stable up-down-up-down pattern) but doesn’t change each time I run the films. But as the films progress, the effect gradually disappears and the sound plays back normally.

Your description indicates the magnetic sound head needs to be cleaned. Use isopropyl alcohol and cotton swabs to clean the the head (and the full path the film takes). Old/defective magnetic recording media (film, cassette tapes, reel to reel tapes) will deposit iron oxide on the heads and affect their ability to play back correctly.

It might also be a problem of "wow and flutter". You can search for that term in regard to tape decks to get suggestions on possible causes.

[Steve Lee]

I was also thinking that it could be that the heads are dirty, as this would cause dropouts to the audio playback. The only problem is that heads on this model 810 D there is no direct access to them. The entire sound head assembly has to be dismantled without touching the Azimuth adjustment in order to have access for cleaning.

[Steve Klare]

Actually cleaning the Eumig 800 heads isn't that hard:

Cleaning 800 Series Heads

In this case, I'd guess something more like a set of contacts somewhere in the audio circuitry. There are weak signals and a little oxide on a switch contact or volume control slider can make for trouble. The thing is to work switches and jacks repeatedly: they often can self-clean. The red recording switch is a big one on Elmos, but I've sen it silence a Eumig at least once.

I've been working with contact cleaner spray for the first recently and been impressed with the results. The problem there can be access to the contacts.

[Maurice Leakey]

[QUOTE=Steve Klare....The thing is to work switches and jacks repeatedly: they often can self-clean...[/QUOTE]

How about the N-S selector switch?
Perhaps a little working of this may help.

[Steve Klare]

I'd say anything audio is worth trying!

The first time I had one of these adventures I had a mute Elmo ST. I figured I'd divide and conquer, so I plugged in a set of headphones and see where the sound stopped. After I plugged in I got sound. After I unplugged I got sound through the speaker too. It was the switch in the jack. (It's nice when they give up without too much of a fight...)

[Shane C. Collins]

This reminds me of drop-outs, and other noises associated with audio equipment that I've had over the years. I have several reel to reel tape recorders that will occasionally give static noises, and some low audio drop-outs. Most of the time it's oxide on the volume, record, and bias switches. Some contact cleaner, or rotating the dials 30 times will fix the issue. And some times it's a dirty play or record head. I've even had to demagnetize the heads to resolve background noises. So yes this could be your issue.