8mm Forum: Speed Problem on Elmo St-1200

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Posted by Adam Schultzman (Member # 712) on October 22, 2010, 09:35 AM:

hey all...
im having a re-occurring speed problem on the elmo st-1200 that i bought recently. it works fine when 18 fps is selected...yet when i try to switch to 24 fps, there is a problem... it actually runs slower than 18 frames/second instead of 24 fps! This problem *only* happens in the forward projection mode. in reverse projection, it works like it should (and *does* seem to run at 24 fps). its like this the majority of the time, which is super unfortunate since i run alot of sound film. i was told that all the belts were changed sometime in the last 2 years....Does anyone have any ideas on this issue? why would it work in reverse but not forward? anyhow, let me know if folks have any ideas. thanks!
~adam

Posted by Steve Klare (Member # 12) on October 22, 2010, 01:54 PM:

I feel your pain...

Literally: I have the same machine and I'm fighting the same issue. (-not nearly as bad though...)

I've made some progress on it. A lot of people think the ST-1200 really likes getting regular run time and doesn't do well when stuck in long-term storage. Mine had been on vacation a few months because I didn't feel like fighting this problem last Summer.

So last Saturday I started it running at 9AM with the lamp off and no film and I shut it off a little after noon. (...wanted peace and quiet while I ate my lunch!)

It does seem better now. Sometimes at the beginning of a reel it's a little slow but soon it's normal sounding.

Wild Guess: In forward projection with film loaded the pinch roller clamps the film down on the flywheel roller and there is more drag for the transport mechanism to fight. In Reverse the pinch roller is raised away to allow the film to move without engaging the flywheel.

Q: Does the machine seem slower in forward vs. reverse without film?

PS: Please make sure that bigger black roller is pressing firmly on the shutter wheel when you are going for 24FPS and for Heaven's sake don't walk out on a 35 year old machine operating long term unless your fire insurance is paid up!

Posted by Roy Neil (Member # 913) on October 22, 2010, 10:44 PM:

That pinch roller at the soundhead should not cause significant drag. The flywheel gets up to speed by means of a small rubber roller that disengages after a few seconds once the projector is switched into forward.

A friend of mine sent me his projector that was having the same problems. The pressure of the rubber rollers against the shutter may be an issue - try pulling the wheel away a tad to see if that speeds things up. Also the camtank may need to be cleaned/lubricated. I used a teflon based waterproof grease ( plastic compatible ) to lubricate the camtank. After that it ran perfectly.

Posted by Dino Everette (Member # 1378) on October 23, 2010, 01:05 AM:

I actually sold Adam that projector, and I ran it a bunch before sending it to him and it worked great, but I have had the slow down issue with elmo's before and usually I just put the machine in reverse for a couple of seconds and then put it in forward and I have always had that work... Is it possible that the little roller that moves when you switch speeds is not connecting firmly...Also Roy do you have a picture of the area you mentioned that should be cleaned?

Posted by Steve Klare (Member # 12) on October 23, 2010, 06:00 AM:

I'm not saying that the addditional drag of the flywheel would be huge, just a little bit more, and maybe just enough to push the thing over the edge.

Basically this machine depends on friction, and I'm thinking of the friction between the rollers and shutter wheel in particular. There are two kinds of friction: static and kinetic. Static is when you step on your brakes and the tires are still rolling on the pavement. Kinetic is when you panic and step too hard on the pedal and go into a skid. This is bad because kinetic is always less frictional force than static and you won't stop as fast (-there is the steering thing too, but that's beside the point here.)

The idea was that Adam may be putting his ST-1200 into a "skid" going forward and that last bit of drag that pushed him over the edge could be the extra drag of starting the flywheel going from a dead stop.

-So now the roller is slipping on the shutter wheel and the machine is slow because of it.

I've noticed the problem more after a switch from 18 to 24 FPS so maybe Dino is right an the roller isn't seating consistently and it takes a couple of seconds in reverse to wedge it in place. I've noticed some slop in the rocker mechanism, so maybe it's not certain how much pressure there is between the roller and the shutter wheel.

It could be a combination of his idea and my idea.

Roy, I don't understand what a camtank is. Please explain: waterproof teflon grease is ready when you are! Once again: every last bit of drag may count.

I'm looking forward to literally getting mine "up to speed": these are great machines and there 's a lot I can do with it once it's right.

[ October 23, 2010, 07:05 AM: Message edited by: Steve Klare ]

Posted by Adam Schultzman (Member # 712) on March 29, 2011, 11:53 AM:

Hey steve...
did you ever have any success in repairing your st-1200 projector? I'm finally getting around to working on mine...I tried fooling around with the pressure of the rubber wheels on the shutter but changing the pressure had little to no effect on the speed problem i have. anyone know what a "camtank" is? or how i would clean/lubricate it? or the name of a decent waterproof teflon grease (can you buy it at a hardware store?). let me know. thanks!
~adam

Posted by Steve Klare (Member # 12) on March 29, 2011, 12:17 PM:

I have mine to the point where at the beginning of the first reel the audio is a little too bassy, but within a minute it's at least close enough to 24 FPS that I can't hear the difference. This is the same for every reel that follows while the machine is still hot.

One thing I do which seems to help is I set up my projectors first and let the ST-1200 run empty and unlit while I round up films and pull the screen down.

I have the parts and the circuit design for a widget that would allow me to read the light pulsations coming out of the lens directly as FPS. Someday I'll build it and see for certain what's going on.

-After I finish my audio interface, and fix the wallboard around the air conditioner, and straighten up the mess in my backyard...and wax my car, and clean the gutters...and edit some films...and...and........

I haven't pursued the camtank issue...yet.

Posted by Roy Neil (Member # 913) on March 30, 2011, 03:56 PM:

Sorry for not seeing this more soonerererer ...

The camtank is the thingy that houses the cam, which the arm rides and which causes the pulldown claw to move down, in, up, and out - hows that for a technical description ? [Smile]

Remove the back of the projector, look at where the shutter attaches in the center. The shutter is attached to the cam, it is what causes the cam to turn. If you get a flashlight and look in there, you can probably make out a piece of foam rubber jammed in there which is meant to act as a 'lubricant reservoir'. Typically these are bone dry, and I use some teflon based grease ( just a tad ! ) to re-lubricate the cam, and any excess is sucked up into the foam rubber so now it has a little in the 'reservoir'.

To properly work on this area of the projector it really needs to be removed ... which is not trivial. I started to type steps and I realized its too complicated to type out here.

The slow down on these projectors can come from too much tension on the shutter wheel. The rubber wheels are designed to 'just touch' the shutter, not bear down against it with great force - too much force and it causes the mechanism to bind and slow down.

I have one machine that is kind of like my own personal pet project, it has been a huge restoration effort and still is not 100% - although - it works well enough for me to use and as such has become my primary machine of late. I noticed that until the machine is 'warmed-up' the film will run slowly, even though everything is in top condition. After it runs for about 2~5 minutes, there is no speed problem - until the machine is powered down for more than 2 hours, at which time it reappears. Since the problem only exists for 2~5 minutes it makes diagnosing the issue very difficult, as you must now wait 2 hours to re-examine, or, test a solution. After a year ... I have finally determined that it is the motor itself. I would warm up the machine by putting it in forward for 2~5 minutes, however, I have learned that only the motor needs to be activated, not the mechanics. I was under the impression that the mechanics itself were 'stiff' however it appears the motor itself will not achieve full torque until warmed up.

The take-up mechanism is another source for temporary speed problems. This is designed to 'slip' and if there is too much friction it can cause the machine to 'bog' until the clutch slips more freely. Do not put lubricant on the cork pad in the clutch ! it needs to be dry - if anything use a very small amount of teflon powder, do not use grease or oil !

Sorry for the lengthy and hasty post, Im short on time but I wanted to post a reply

Posted by Tony Stucchio (Member # 519) on March 30, 2011, 05:59 PM:

Both of my Elmo ST1200 HDs take about 5 minutes to warm up to speed. I put it in full forward gear to do this. Another method is to watch a short silent film!

[Smile]

I really don't like the rubber wheel design. Does the GS1200 have this as well, or is this unique to the ST1200s?

Posted by Steve Klare (Member # 12) on March 30, 2011, 06:35 PM:

The AC motor and roller speed control are definitely the weakpoints of the ST-1200.

The "lesser" ST's have a DC motor and an electronic regulator (I think the GS does too...) which once you dial it in is steady as a rock.

It's a shame Elmo just didn't do the same thing for the ST-1200.

Posted by Adam Schultzman (Member # 712) on July 08, 2011, 09:54 AM:

hey roy...
im finally getting around to trying to work on this issue again. i'm looking at what i believe to be the cam tank (following your description). I looked all around but I did not seeing any kind of foam rubber/reservoir. is there any chance you or someone else could post a picture of where exactly this is? help me obi wan, your my only hope!
~adam

Posted by Julian Baquero (Member # 2520) on July 08, 2011, 11:55 AM:

This might seem stupid, but it happen to me. Open the projector and check the position of the belts, it must be different for 50 and 60hz (USA/Europe). My projector had a brand new set of belts when I bought it, but the owner set the belts in the 50hz position, here in Colombia we use 120V/60hz as in the US, I noticed terrible sound and lag, until I open the cover and check the belts I noticed the were in the wrong position. I change the position of the belts and problem solved. The ST1200 as some have said before need some warming up to get to speed.

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