Bad crackle when running film on Elmo ST1200HD

[David Monard Ice]

Recently, I have had a rather severe problem with audio crackle when I am running film on my ST 1200 HD projector. In terms of sound, there is no crackle when I turn the projector on, nor is there any crackle when the projector is running forward but with no film threaded. But once there is film threaded it sounds like hail on a tin roof!

The only thing I did was clean everything with a Q-tip and isopropyl alcohol a week or so ago. But this crackle now is enough to make a film unwatchable due to the horrible sound. Any comments or suggestions? I have another identical projector, and everything sounds fine on it.

Thanks for your help!

[Rob Young]

Hi David, we have discussed crackle on the Elmo ST1200HD before as it is caused by static and it is a fairly common trait, although of course it should not be as bad as you describe. In fact, when it does occur it should be a mild annoyance at worst. But the symptoms you describe with crackle only when running a film does make it sound like static.

It can originate from the brass capstan roller just after the sound head and sometimes just lightly touching the side of it when running a film (with care) can help.

Other thing to try is putting the machine in and out of record several times as this can demagnetize the soundhead. And give all the rear switches and knobs a few pushes and twists too.

You can buy a demagnetizing tool reasonably cheap which you hold against the sound head and capstan roller and gently move away to demagnetize them, but then again, your case does sound as if something more is to blame.

So just a couple of quick things to try until someone else has any good suggestions (my only other thought would be something that supresses the motor has failed, but that's well beyond my pay scale).

[Steve Klare]

Hi Dave,

There is an experiment you can try, especially if you are using the Aluminum ELMO take up reel.

I've developed this suspicion that the static discharge is caused by the film getting dragged across multiple surfaces and then when it piles up on the take up reel, the charge does what like-charges do and pile up as far apart as possible. When enough of them gather on the reel the voltage rises up to the point where it arcs to ground through whatever is the easiest path.

If you have an aluminum reel, please run a film in full crackle-mode. Hold a piece of wire on some bare metal surface of the machine (-mounting screw, maybe?) and also drag it lightly on the metal reel surface and listen if the popping stops. (-or even just changes.)

This theory is currently just a wild-guess. You have the chance to show if there is any truth to it at all!

What's interesting is I always think of this being a winter problem because the dry air prevents the gradual discharge of built-up static. Then again, from my years working at a factory in Tucson, I remember "Arizona is a dry heat!".

[Paul Adsett]

Does the ST1200 have a copper grounding strap, contacting the end of the rotating Flywheel/sound drum shaft, as in the GS1200?

[Rob Young]

They don’t, Paul. A later mod was a capstan roller which has a rubber coating on it which certainly helped mine.

One rather rough fix back in the day was to go into the back of the machine and secure a piece of thin wire to the projector body and rest it gently on the capstan to act as an earth. Never thought much of that, although it probably worked. But it never crackled to the point that David’s is.

[Steve Klare]

Hi Paul,

I'd think the metal roller would be a pretty decent ground through its chassis mounted bearing, and also the lower sprocket has got to drain some stray charges off. (Then again, there is the entire gate!)

Where I wonder about is the long guide between lower sprocket and the take up. Everything is insulated material and there we go dragging film through it.

How about this?

Where there's an arc, there should be a spark!

How about Dave projects a film in a darkened room with the side panel open and the projection lamp off but the sound turned up?

-he can just sit there and look for blue flashes that coincide with the "pop"s. I'm not 100% sure they would be big enough to form literal lightning bolts ("-Kill the Wabbit!"), but what's the harm in trying?

[Leon Norris]

David is the crackling noise coming from the amp or the motor? I have fixed many ST1200 models. I know about the Elmo projector pretty good.

[David Monard Ice]

[QUOTE=Rob Young;n119644]Hi David, we have discussed crackle on the Elmo ST1200HD before as it is caused by static and it is a fairly common trait, although of course it should not be as bad as you describe. In fact, when it does occur it should be a mild annoyance at worst. But the symptoms you describe with crackle only when running a film does make it sound like static.

It can originate from the brass capstan roller just after the sound head and sometimes just lightly touching the side of it when running a film (with care) can help.

Other thing to try is putting the machine in and out of record several times as this can demagnetize the soundhead. And give all the rear switches and knobs a few pushes and twists too.


*******

Hi Rob! Thank you so much for your help. For some reason I have real problems navigating things on this site (it’s just me I guess). I did try to look for crackle or static threads or links, even going to the Google to try to find anything, and I couldn’t. Hence my post here.

I just wanted to say that I tried popping things in and out of record about eight or 10 times ans you suggested and voila! The hail storm stopped! Thank you so much for such a quick and easy fix!!! I am also going to demagnetize the sound heads and capstan roller as well.

I am a retired sound effects editor, and I have felt a strong pull to get back into Super 8 after neglecting it since the mid-1970’s or so. I started film collecting when I was just a kid, and was thrilled to find a black-and-white Super 8 magnetic sound print of the first film I ever owned – – Woody Woodpecker in NIAGRA FOOLS!!! I probably hadn’t seen that cartoon in 60 years and it really took me back down memory lane. Of course I was used to seeing it silent and at 18fps, but it was still a huge thrill to see it properly!

I love the feel of film in my hands and projecting an image that came from celluloid, not microscopic pits on a DVD or Blu-ray. So I sincerely thank you for your help in continuing my long neglected hobby of super 8 mm film.

[David Monard Ice]

David is the crackling noise coming from the amp or the motor? I have fixed many ST1200 models. I know about the Elmo projector pretty good.

This projector is really really noisy when you first turn on the amp. It crackles very loudly for about five seconds until it settles down and after about a minute it seems to settle down and go away. It is very annoying to start a show and have to mute the speakers somehow to let the amplifier stop it’s tantrum and do its job! Any suggestions would be appreciated! I have another Elmo ST 1200 HD that isn’t nearly as noisy when you turn on the amp.

[David Monard Ice]

Hi Dave,

There is an experiment you can try, especially if you are using the Aluminum ELMO take up reel.

I've developed this suspicion that the static discharge is caused by the film getting dragged across multiple surfaces and then when it piles up on the take up reel, the charge does what like-charges do and pile up as far apart as possible. When enough of them gather on the reel the voltage rises up to the point where it arcs to ground through whatever is the easiest path.

If you have an aluminum reel, please run a film in full crackle-mode. Hold a piece of wire on some bare metal surface of the machine (-mounting screw, maybe?) and also drag it lightly on the metal reel surface and listen if the popping stops. (-or even just changes.)

This theory is currently just a wild-guess. You have the chance to show if there is any truth to it at all!

What's interesting is I always think of this being a winter problem because the dry air prevents the gradual discharge of built-up static. Then again, from my years working at a factory in Tucson, I remember "Arizona is a dry heat!".

****

Believe it or not static is a real problem – – at least for me. I’ve learned how to be very cautious when I have to go to a doctors office or some other building because I will get static discharges like crazy. Very visible blue, arcing electricity between my finger and the elevator button or the door knob or whatever. It doesn’t matter what kind of shoes I wear or what the surface of the floor is either!! It feels like I’m electrocuting myself no matter if I’m walking on tile, marble, industrial carpet, or even Cement. Rubber or leather shoe soles don’t seem to make any difference.

For what it’s worth, my brother-in-law has to carry a pocket watch because he has so much electricity built up in his body that a regular wristwatch, even a digital one or an Apple Watch, won’t work because of his body electricity.

That said, I have never felt an electrical spark between me and the projector. It could be because I’m not moving or walking while I’m running a movie—or there isn’t enough charge built up to do the blue arc of lightning. But I’ll pay special attention next time I just walk up to the projector and touch a metallic part. Can you get static discharge flashes between a human body and aluminum? I’ve never pondered that!

[David Monard Ice]

Where there's an arc, there should be a spark!

How about Dave projects a film in a darkened room with the side panel open and the projection lamp off but the sound turned up?

-he can just sit there and look for blue flashes that coincide with the "pop"s. I'm not 100% sure they would be big enough to form literal lightning bolts ("-Kill the Wabbit!"), but what's the harm in trying?[/


I LOVE LOVE LOVE thunderstorms, especially our Arizona monsoon storms, which can be quite spectacular! I will sit in total darkness and see if my projector can conjure up a miniature thunderstorm for me!

[Leon Norris]

It sounds like the amp assembly needs a good cleaning. I use tuner cleaner with lubricant. That will take care of the problem.