8mm Forum: GS-800 popping sound

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Posted by Vidar Olavesen (Member # 3354) on April 23, 2013, 01:51 PM:

Anyone know what could cause this? At random intervals the speakers go popping. Quite annoying. Anyone have a clue?

Thanks

Posted by Steve Klare (Member # 12) on April 23, 2013, 06:31 PM:

Sometimes it's electrostatic discharge between the film and the projector frame. This is usually worst in the winter because the air is dryer.

I have one film I have to keep away from my ST-1200HD because it pops like crazy, but any other film in that machine or that film in any other machine is just fine.

(I think maybe this film is acetate based and almost all the films I run through that machine are polyester based.)

Some sound tracks just come with their own clicks and pops. If it happens the exact same way every time you project the film, that's probably what you have.

Posted by Vidar Olavesen (Member # 3354) on April 23, 2013, 06:37 PM:

Nope, it's not the film ... Works fine in the GS-1200. And it's random intervals, I think.

Needs grounding I heard someone say ... But I don't know where and how ... Anyone done it and can do a picture?

Posted by Adam Deierling (Member # 2307) on April 23, 2013, 08:38 PM:

When runnng a film that pops, try touching the last rear metal roller with your finger. Sounds odd but worked on mine. If the popping stops you can connect a short wire from that roller to the frame of the projector. Popping will stop. Hope this helps.

Posted by Vidar Olavesen (Member # 3354) on April 24, 2013, 12:04 AM:

Will check that today ... Thanks

Posted by Ian O'Reilly (Member # 76) on April 24, 2013, 11:25 AM:

Adams cure will work, I cured many GS800's this way.

Posted by Hugh Thompson Scott (Member # 2922) on April 24, 2013, 12:00 PM:

I used to experience the same thing on the ST1200s when cleaning films mounted on metal spools,the spark could be seen discharging between spool and arm of projector, just static.

Posted by Vidar Olavesen (Member # 3354) on April 24, 2013, 12:29 PM:

Anyone have a picture of the solution?

Posted by Adam Deierling (Member # 2307) on April 24, 2013, 12:59 PM:

This is a picture I took a while ago enlarged to show the wire. I don't have this projector anymore otherwise Id open the door and take another picture for you to see where it attaches inside. But I'm sure you can find a screw to attach it to.

Posted by Vidar Olavesen (Member # 3354) on April 24, 2013, 01:00 PM:

Ah, okay, I thought it was the one inside the projector ... Thanks ... Will try to fix something to it and see :-)

Appreciate the picture

Posted by Lee Mannering (Member # 728) on April 25, 2013, 07:15 AM:

Done a few of these.

Remove front drop down cover
Remove green film guide which you will need to carefully un-screw along its rout.
Run a single strand of wire (I strip back a length of mains lead for this) and right along the back of the green film guide you need to have the wire make contact with each rollers screw that is screwed to the green guide.

I remove the large metal bracket at the top end of the green guide and start the wire behind it. Gradually work your way down and finally secure the wire along the back of the guide with insulation tape. If done neatly and right it works every time.

Posted by James N. Savage 3 (Member # 83) on April 26, 2013, 06:40 AM:

My Sankyo ST-800 does this too, usually after 60 - 90 minutes of projecting. A single pop, every minute or so.

James.

Posted by Steve Klare (Member # 12) on April 26, 2013, 07:36 AM:

I wonder if the real problem here is the film rubbing against that long plastic guide just before the exit and maybe against the flanges of the takeup reel: building up charge.

I went over the projection path of my ST-1200HD with an ohmeter, all of this is already metal and grounded to chassis:

-top sprocket
-gate and pressure plate
-sound heads
-bottom sprocket

There shouldn't be any buildup of charge in this part of the path, but then you have this long plastic guide with a plastic roller at the end, then you can throw in a plastic reel that may rub once a turn as a bonus.

-rubbing an insulator on an insulator (film on plastic) is a classic recipe for static electrictity.

It would be interesting to see the difference using a metal reel makes. I'm using an Elmo 1200 footer right now, I'll have to swap it with my old plastic reel and see.

Posted by Vidar Olavesen (Member # 3354) on April 26, 2013, 09:21 AM:

I tried putting my finger on the roller where I was told to, no help. Seem to stop when I put my finger on the metal take up reel (metal ... maybe not so good?) and it didn't pop a single time on my 800' Smokey and the Bandit yesterday, but I put on a Donald Ducks Dilemma (I think this was the one I noticed on a couple of days ago too) it pops again ... Yeah, about every minute or so, but not like clockwork, sometimes earlier, sometimes later

Posted by David Ollerearnshaw (Member # 3296) on April 26, 2013, 10:02 AM:

Not sure if it applied to all ELMO ST/GS series projectors, when mine went back to C.Z. Scientific for a service. It had the same problem, they fitted a modification to it. Basically they fitted an earth to the flywheel, it cured the problem.

They told me due to the grease drying out that's what caused the static. Don't know if it was true, but like I say it cured it.

Try using a bit of wire and put one end on some bare metalwork on the casing and touch the other end lightly on the end off metal roller where the sound heads are.

The fix they did was inside though.

Posted by Steve Klare (Member # 12) on April 26, 2013, 10:24 AM:

I think a plastic reel would be worse, especially if it rubbed on the film while it turned. The problem here is the metal reel is ungrounded, so it can't drain off the accumulated charge. All it would do is take the charge off the film and they'd accumaulate out on the outer circumference (-because they repel each other)

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