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Topic: Unusual travel ghost problem

Ross Peard
Film Handler

Posts: 2
From: San Jose, CA, USA
Registered: Jul 2002

posted 07-31-2002 02:08 PM

I'm running a Century C with an 2K L.P. assoc. lamphouse, and I can clearly see travel ghosts coming down from the top, AND up from the bottom. No my shutter doesn't have any holes in it. This occours for both flat and scope features. What could be causing this and how can I fix it?

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William T. Parr
Jedi Master Film Handler

Posts: 823
From: Cedar Park, TX
Registered: Nov 2000

posted 07-31-2002 02:22 PM

Is the ghost a constant travel ghost or does it seem to pulsate meaning the ghosting gets large than small than large than small. If that is the case you have a gear shaft opening on the intermitten or shutter that is getting wallowed out and is not perfectly round or tight fitting anymore. Had that problem at my theatre on a Cinemacannica about a month ago.

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Dick Prather
Master Film Handler

Posts: 259
From: Portland, OR, USA
Registered: Feb 2002

posted 07-31-2002 02:28 PM

A couple of things that can cause that are:
Your shutter blade cut or is too narrow.
Needs to be a 90 degree blade
Loose gear train or gears no mating properly.
Check the shutter shaft for bouncing back and forth.
Check the vertical shaft for bouncing up and down.
Problem with all Century's over time is the vertical shaft coming slightly loose causing movement in the shutter shaft every time the intermittent pulls down.
If you find your problem above we can then offer solutions.
Dick

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Michael Barry
Jedi Master Film Handler

Posts: 584
From: Sydney, NSW, Australia
Registered: Nov 1999

posted 07-31-2002 02:33 PM

I'm thinking that the shutter blade may not be covering the aperture fully, like in a 'drive-in' shutter. That would certainly be one way in which the shutter would be simultaneously too early and too late.

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Ross Peard
Film Handler

Posts: 2
From: San Jose, CA, USA
Registered: Jul 2002

posted 08-01-2002 01:48 AM

The ghost's look just like normal travel ghost's, (i.e. if you were to turn your shutter knob to make the machine run out of time.) This head was re-built four or five years ago, and I understand that normal operation should not result in significant wear of gears, etc... (it was rebuilt in portland if that makes a difference.)
This machine has run for years without problem.
I'm not nearby now so I can't tell you if anything's loose in the non-operator side.
My original theory was that we had light reflecting somehow, as we did not have a problem before we upgraded from a 1.5 to 2k lamp. But , maybe more light just illuminated an existing problem?
I'll have to check the machine and reply about loose shaft's, etc..
thanks!

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Dick Prather
Master Film Handler

Posts: 259
From: Portland, OR, USA
Registered: Feb 2002

posted 08-01-2002 03:13 AM

If you work for Dennis then I probably rebuilt your projector. If you want to send me the serial # I can see what was done during the rebuild. When you increase the light output you will see more defects. Some drive in's had shutter blades really cut down and because of low light a travel ghost never would show. When you get time let me know about the shafts moving. When you turn the shutter knob does the ghost you are watching get worse either top or bottom?
Dick

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Dave Ganoe
Expert Film Handler

Posts: 119
From: Point Marion, PA
Registered: Jun 99

posted 08-01-2002 04:53 AM

I recently upgraded my lamp from 750w to 1600w and not I too have a ghosting noticable with credits or white parts of the image. It is a simplex super. When adjusting the shutter best you can get is where it is ghosting in both directions but not consistently and not terribly. The shutter blade is adjustable but seems not to be set to small.

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Pat Moore
Master Film Handler

Posts: 363

Registered: Mar 2000

posted 08-01-2002 07:41 AM

Hi; I think Dick has it covered on shutter blades, gear mesh, etc. The increase in light may made the problem more obvious as well. For indoor use with proper illumination, that shutter should be 90-degrees or very close to it to eliminate ghosting.

One other consideration -- after being sure the shutter is correct -- s the lamphouse. Is the working distance correct? If it's too close the angle of light coming into the machine might be too large. That is, the circle of light where the shutter wants to interrupt it is too large a diameter. I don't know what LP's proper working distance is, but if you have the time you might pull the lamphouse back one-half or even one inch and see what difference, if any, that makes.

Pat

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Steve Guttag
We forgot the crackers Gromit!!!

Posts: 12814
From: Annapolis, MD
Registered: Dec 1999

posted 08-01-2002 08:18 AM

Anyone that claims that normal use of a Century projector does not result in wear on the gears is telling a falsehood. With the exception of the sprocket drives all of the other gears have unfavorable gear ratios. That is, larger gears driving smaller gears. It is not uncommon to change out main-drives, shutter drives and intermittent drives (with the intermittent, sometimes it is the key and slot that are worn out).

But I must side with the others on this one...I'd make sure I have at least the 90 degree shutter blade (C1-D-48). It will cure most shutter ghost ills. If light is available, the C1-D-50S is a real winner...it is 100deg and is made from thin steel...doesn't seem to warp and provides a better flywheel effect.

Steve

------------------
"Old projectionists never die, they just changeover!"

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 08-01-2002 12:09 PM

If you have ruled out all the other things with negative results check the gears and shaft in the back of the projector. Especially the vertical shaft.

On one projector I used to work on, some butt head decided to try to clean out the gear compartment but didn't shut off the motor. Well, the red shop rag got caught up inside and did a job on the vertical shaft. It was bent just enough to make it go "Wooga-Wooga" and cause the shutter timing seem to fade in and out.

Of course, nobody would admit to it. If I ever get my hands on that Nobody guy...

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Mark Gulbrandsen
Resident Trollmaster

Posts: 16657
From: Music City
Registered: Jun 99

posted 08-01-2002 12:17 PM

Cinerama 3 strip machines had an interesting shutter in them. The blade actually floated on the hub and it was coupled to the hub by 4 springs. Not sure why they did this but it must have had some sort of filtering effect. I like the idea of the steel blade the best. Strong dod the right thing by going to this design which is similar to the way the original JJ's were made. IN the case of the JJ's they had dual steel shutter blades that were quite thick...mainly to take the heat of huge arc lamps, but it also added a highly desirable flywheel effect to the mechanism and smoothed things out alot. In fact these are among the most desirable JJ's to own if any of you are looking the market or one. Usually under ser# 500.
Mark G.

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