Film-Tech Forum ARCHIVE: JItter and ghost, shutter knob "racked"

This is topic JItter and ghost, shutter knob "racked" in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

To visit this topic, use this URL:
https://ft-forum.com/ft/cgi-bin/ubb/ultimatebb.cgi?ubb=get_topic;f=1;t=010833

Posted by David E. Nedrow (Member # 4981) on 03-05-2011, 10:25 PM:

Our number one projector has developed a pretty bad gate jitter with some ghosting. I am able to clear most of the ghosting, but it requires the I turn the shutter adjusting knob all the way to the right. Even then, there's still a bit of ghost.

Regardless of the shutter knob setting, I cannot get the jitter under control. I've tried the trap tension knob, but no luck. This projector (Simplex XL) has always been a little unsteady, though there isn't any weave to speak of.

It seems as though I may need to work on the shutter. Anything else I should look at before going for the guts?

Posted by John Wilson (Member # 269) on 03-05-2011, 10:36 PM:

Is it noisier than usual also?

Posted by Joe Redifer (Member # 3) on 03-05-2011, 11:21 PM:

Sounds like the intermittent might be going bad. How are the oil levels? Also, have you tried re-timing the shutter by hand? That way you might be able to turn the knob enough to get rid of the ghosting. The allen screws that hold the shutter on to its shaft may also be loose.

Posted by Monte L Fullmer (Member # 2797) on 03-06-2011, 01:17 AM:

...or the shutter drive gear being a fibre gear...

..or the vertical shaft isn't aligned correctly - with the upper section just barely meshing with the shutter drive gear creating too much slop.

Any brain wraps with this machine in the past? Wraps loves to knock things out of kilter with the machine when that film loves to make the machine suddenly work much harder than required..

Posted by Tony Bandiera Jr (Member # 2365) on 03-06-2011, 01:58 PM:

Ok class, time for the Simplex XL shutter timing tutorial:

1: Remove sight box cover to access shutter hub and setscrews.
2: Set the shutter adjust knob to the middle of it's range.
3: Set the FRAME knob to mid-travel. (I'll explain why later.)
4: Loosen the shutter hub setscrews just enough to allow the shutter to turn with a good amount of drag on the shaft. It should NOT turn freely.
5: Now, using the hand incing knob or flywheel on the motor, carefully step the intermittent movement EXACTLY TWO sprocket teeth from the dwell (at-rest) position.
6: Holding on to the flywheel or inching knob so the mechanism can't move, CAREFULLY rotate the shutter so that one blade is EXACTLY centered over the aperture hole.
7: Tighten the shutter hub setscrews. If they are in a position that is not accessible (and IF you left them tight enough on the shaft so the shutter can't freewheel,)slowly turn the machine over by hand until you can get to the setscrews and tighten them up. Be careful not to rotate the shutter while doing this.
8: Turn the machine over by hand several frames then repeat step 5 and verify that the shutter's blade is still centered over the aperture area.

Now, why did I include step #3? Because the XL mechanism includes a shutter timing compensator for the varying positions of the frame knob, necessary since the intermittent sprocket physically rotates to change frame position. Setting it to mid-point (as well as the shutter adjust knob) will ensure that you have maximum ability to compensate for timing errors.

After doing all the above (which actually takes less time to do than it took to read), start the machine with no film.

From the NON-OPERATING SIDE, use a flashlight and watch the steel gear on the shutter drive assembly. As you turn the FRAME knob from one extreme to another, it should slide back and forth on the shaft SMOOTHLY with NO BOUNCING OR JERKING. If it bounces or jerks, the thrust spring in the shutter drive is bad and needs to be replaced. I offer rebuilt shutter drive assemblies on a repair-exchange basis.

In extreme cases of bad thrust springs, the bouncing of the shutter as it runs (especially with two-blade drive-in shutters) will result in travel ghosting on both the top AND bottom of bright images.

If the steel gear isn't bouncing around, then it is possible that, like Monte suggested, the fiber gear is worn or the vertical drive shaft is mis-aligned and causing slop.

Posted by David E. Nedrow (Member # 4981) on 03-06-2011, 03:19 PM:

The projector isn't any noisier than usual. In fact, it's a lot quieter than when I took over the place. It's amazing what removing rust from high rotational velocity pieces can make in the smooth operation of a machine. [Wink]

Oil levels are fine. No brain wraps, since we don't run platters, but there is something similar with the spool towers, which HAS happened recently. Fortunately, I was in the booth when it happened. The jitter had been there prior to that, so I don't think it caused a problem.

I was about to verify the shutter timing, as suggested. It's probably the simplest thing to check first. Thanks for the other info, Tony, re: the shutter drive assembly.

-David

Posted by David E. Nedrow (Member # 4981) on 03-07-2011, 08:36 PM:

OK, adjusted the shutter positioning. It was WAAAY off. Probably 10 degrees. No wonder I couldn't fine tune it with the shutter adjustment.

So, the ghosting I can handle now. But I still have the vertical jitter.

I'll look at the drive assembly next.

Posted by Chase Pickett (Member # 5975) on 03-07-2011, 09:37 PM:

Also, check the sprockets on the intermittent. I've had issues with a vertical jitter from a hooked sprocket.

Posted by Monte L Fullmer (Member # 2797) on 03-07-2011, 10:10 PM:

Are your machines either the flat rail type or the curved gate/ steel band type?

I can see jitter with worn rails if the setup is the "flat trap" kind.

Also, if the picture looks kinda "pulsating", it could be a bulb that is focued too tight where it's more focused on the shutter than the aperture...

Posted by David E. Nedrow (Member # 4981) on 03-11-2011, 06:40 PM:

Monte, these are curved gate/steel band.

I believe that I now have the position of the shutter "perfect". I still have a ghosting issue at the very top and bottom of the frame. Nothing noticeable -- from the booth -- in the central portion of the image. Using the shutter adjust knob, I can transfer the ghosting from top to bottom, and vice versa, but can not get rid of it. I can get an even amount of ghosting at the top and bottom of the screen if I "center" the shutter adjust knob.

So, thinking about how this all works mechanically, if I have ghosting descending from high contrast material at the top of the screen, and ghosting ascending from similar material at the bottom of the screen, that would seem to indicate to me that the angle at which the shutter is set is too large. This is a standard two-bladed adjustable shutter.

Am I correct in my thinking, in that all I should have to do now is decrease the angle of the shutter until the ghosting disappears?

Posted by Tony Bandiera Jr (Member # 2365) on 03-11-2011, 06:44 PM:

Yes. That will eliminate the ghosting, with some loss of overall light.

Posted by Troy Powell (Member # 5505) on 03-11-2011, 07:33 PM:

Sounds like the shutter blade is burned at the edges.Check for that.

Posted by David E. Nedrow (Member # 4981) on 03-12-2011, 12:10 AM:

Tony, thanks for confirming. Theoretically, this -- shutter angle --would not need changed after the initial setup, am I correct? If so, the shutter either wasn't properly set to begin with, or was diddled with later.

Given who ran this place before, I can easily see a conversation along the following lines:

Owner: "Hey, some guy told me we could get more light on the screen if we open the shutter more."

Employee: "Umm, but that would mean a bunch of ghosting on the screen."

Owner: "They won't notice it with all the extra light. Besides, where else are they going to go to see these types of movies. Give me that screwdriver. Where IS the shutter?"

[Wink]

Posted by David E. Nedrow (Member # 4981) on 03-13-2011, 07:28 PM:

Hmmm, I just noticed that the shutter is moving back and forth a bit. Looking at the non-working side, I can see the shutter shaft operating like a piston while it spins.

When running, #2 does not show this behavior.

What would cause this kind of slop? Do I just need to open the back, hold the shaft in, and push the shutter back on the shaft?

-David

Posted by Randy Stankey (Member # 64) on 03-13-2011, 08:03 PM:

I have the shutter in my Simplex as far open as I dare, even at the expense of a tiny bit of shutter ghost.

I have a 31 foot wide screen and my lamp is only 2,000 watts.

I sat down in the theater and watched a few movies and thought about it for a while. "A little extra light?... A bit of ghost?..." I thinkered a couple of times until I found a setting that split the difference between the two.

No, not a 100% optimum setting but one I can live with. I have never had anybody notice. I have even pointed it out to a few people but they have a hard time seeing it even after I tell them.

The point I'm getting at is, maybe somebody at your theater made the same kind of decision but didn't think about it as carefully.

I suggest you reset it to the "proper" setting then go down and watch a movie and decide whether you want to keep it as-is or modify it.

Posted by David E. Nedrow (Member # 4981) on 03-13-2011, 08:52 PM:

Randy,

I'm pretty happy now with the light/ghost balance. Basically, I have the shutter angle set such that I have zero ghosting when running with the shutter adjusting knob centered. Move that knob a tiny bit either way, and ghostliness ensues.

Probably time to move the jitter issue to a different thread.

Posted by Randy Stankey (Member # 64) on 03-13-2011, 09:19 PM:

Okay, so you have checked your trap?

Clean. All parts that are supposed to be tight are tightened and those that are supposed to be lose are free? Check those lateral guide wheels at the top. If they are not aligned correctly they can cause weave but if they don't spin freely, they can cause jitter. Start at the top of the gate and follow the film path all the way down the gate until the film exits the intermittent.

Check your trap bands and your shoe rails. Clean and tight? The band tensioning screws? The tension adjust mechanism?

Check your intermittent sprocket for hooked teeth. Check your intermittent pad shoe for cleanliness, alignment and proper tension.

It's hard to explain every detail of troubleshooting the film path like this because a lot of it has to do with experience and intuition. Yes, the film path has to be set up in a specific way and, if it's not, trouble will occur but there have been dozens of times when people have reported trouble to me and standard explanations couldn't pin down the problem.

I can't tell you how many times people have reported problems like jitter to me and they couldn't figure out what the cause was but, when I went there, I quickly discovered that there was a piece of crud in the pad shoe or something like that. Often, a well-placed drop of oil was all that was needed.

Go down through that whole gate area, clean it up real good and pay attention to anything that isn't right. It's always a good place to start.

Do the easy stuff first. Right?