Film-Tech Forum ARCHIVE: Century SA travel ghost problem

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Posted by John Westlund (Member # 913) on 12-01-2003, 02:51 PM:

I can't seem to get rid of this travel ghosting problem on our Century SA. I have timed the shutter several times on this machine when changing intermittents etc and never had a problem getting the timing just right. A week or so ago I noticed a ghosting upward problem that occurs only at the bottom of the screen. I have tried twice to time the shutter to get rid of it using the same method that worked in the past and cannot get any better results. Could this be due to excessive wear in the gear train or some minor thing that I am just over looking? Thanks.

Posted by John Pytlak (Member # 331) on 12-01-2003, 02:57 PM:

Excessive play in the gear train usually results in ghosting that drifts in and out, sometimes on BOTH sides of the light objects. Do you feel any play in the gear-train between the shutter shaft and intermittent drive gear? Are you sure that the shutter blades are not damaged (e.g., warped, burned)? Is the blade somehow slipping on the shutter shaft after you time and tighten it? Is the lamphouse distance, focus, and alignment correct?

Posted by Mark Gulbrandsen (Member # 72) on 12-01-2003, 06:38 PM:

John,
Does your projector have a knocking sound when it runs? If so that is indicitave of a bent verticle shaft and will cause the shutter to slip on the shaft even though you've formly tightened it down. If the knocking noise is present replace the verticle shaft along with its matched intermittent drive gear. Also throw on a new shutter gear while you're at it. This is a fairly common problem with Centurys if the shaft was incorrectly installed to begin with or re-installed improperly after a tear down to fix something else. Also check to see that the shutter timming adjustment, knob and associated parts is not real loose and slipping. This camn also cause timing to drift a bit. Another possibility is if you are using a Xetron Lamphouse...there may be spill over at the sides of the shutter. Some models had just a tad too large of cone of light at that point for a Century Shutter necessitating a larger diameret shutter blade.
Mark @ CLACO
P.S. I replaced a bent vert. shaft down in Page, AZ. last Wednesday... its more common than you'd think.

Posted by Dave Macaulay (Member # 813) on 12-01-2003, 11:37 PM:

There's a few things to look at I think. Is the shutter damaged? A hole or burnt edge, or a bad warp - pretty common when the lamphouse is maladjusted or the main dowser is left open with the lamp on - will cause ghosting trouble.
As the geartrain wears it gets looser, and the shutter timing when you do a static setup doesn't easily match the way it runs at speed. Until the gears and keyway are really sloppy it should run OK as the shutter and intermittent drag tend to keep everything on one "side" of the slack; when it's time for a rebuild you start to get the wandering ghost that John describes.
Adjusting the shutter is a pain, as you probably found out. Try turning the machine over forward slowly while feeling the intermittent and watching the shutter, it should be just covering the aperture when the sprocket starts to move and just uncovering it when the sprocket locks up again, the angles should be equal (though reversed). If they aren't, regardless of how perfect the tiiming looks using the pin and notch - it's wrong. If you advance the shutter a bit and do the screws up so the shutter just slips on the shaft then set the intermittent to 2 teeth advanced - turning the machine forward - then turn the shutter (without making the shaft turn) back to where the pin and slot line up and carefully tighten the lock screws... you've hopefully kept all the loose bits on the working side of their looseness. The shutter adjustment should manage to correct any ghosting that remains, just make sure it was centered before you did the previous step.
Since you only have one direction ghosting, I think the machine has a few hours left before it needs new parts. Unless you have wandering ghosting or simultaneously on top and bottom then it shouldn't need expensive surgery to eliminate the problem.

Posted by Michael Rourke (Member # 1142) on 12-02-2003, 12:40 AM:

Make sure the intermittent bearing collar nut is tight, if it is loose it will allow too much play in the shafts and throw the shutter out of time.

Posted by Mark Gulbrandsen (Member # 72) on 12-02-2003, 08:36 AM:

As for setting the shutter.... it is VERY easy on a Century! First set the outboard timming adjustment to the center of its range, then with the shutter loose on its shaft advance the mechanism slowly while holding a screwdriver tip next to an intermittent sprocket tooth. Advance the mechanism till you count the second sprocket tooth and stop. Then align the little V notch on the side of the blade with the large pin thats behind the sight glass and tighten the blade down. This method always results in perfect timming and the outboard adjustment will give you timming adjustment on both sides of dead center.
Mark @ CLACO

Posted by John Westlund (Member # 913) on 12-02-2003, 11:38 AM:

The way I learned to time the shutter was a different way. I learned to first take the shutter blade loose from the shaft. Then advance the machine until the screw holding the intermittent flywheel is parallel with the vertical shaft. Then align the notch in the shutter blade with the pin in the sight glass. This has always worked for me perfectly but I will try these suggestions when I get back to town on Thursday.

Posted by Bob Koch (Member # 1062) on 12-02-2003, 01:22 PM:

John: Do it the way Mark describes to you. That must be an old instruction book you have that describes the method you use in it. Its very poor, in my opinion. The "Mark" method works best on any projector. "Advance 2 teeth and set shutter to block light path".

Posted by Paul G. Thompson (Member # 655) on 12-02-2003, 02:01 PM:

John, Mark's method is the most accurate way to do it. I might add that you should insure the fine shutter adjust carriage is set in its mid-position before you time the shutter.

Since you have only a little ghosting, the fine adjust knob should be able to take care of that.

If you have a pulsating ghost, your machine is not feeling very good. A pulsating ghost is caused by shutter bounce and usually indicates some warn gears, rough gears and/or bearings or improper shaft (vertical and/or shutter) loading.

Posted by John Hawkinson (Member # 1135) on 12-02-2003, 09:17 PM:

Does the SA have a fire shutter? If so, perhaps it is falling into the image? That can look like travel ghosting at first.

--jhawk

Posted by Mark Gulbrandsen (Member # 72) on 12-02-2003, 10:32 PM:

Paul,
The shutter bounce I experienced last Wednesday in Page, AZ and on numerous other occasions always turned out to be a bent verticle shaft. Most common cause of a bent shaft that I've found is improper re-installation of the shaft at some point after a tear down for major cleaning or what ever other work may have been done. Ususally the area where the intermittent bearing block is clamped by the two allen screws is full of white paint and some people don't clean away the paint and will literally force the block back in place distorting the vert. shaft without realizing they've done it. Also the bearing block mounting pads should be free fomr paint and other debris. The only way a Century can function properly is if everything is sitting flat when its tightened down to the main casting. LaVezzi has a C2-G-93 replacement vert. shaft thats made from hardened stainless steel that is so well made you could pound nails in with one [Cool]

, these have never failed on me yet in the field.

Over the past couple of years I've encountered a number of LaVezzi SA Star Wheels that had slots which were a bit to tight. Although these movements almost always run hot, literally,not everyone may catch this. This can also cause excessive loading back on the mechanism during pull down and cause shutter bounce. Lapping the slots out slightly with lapping powder on a glass plate takes care of this problem. I actually had one of these today when I rebuilt an SA movement in the shop!!

Mark @ CLACO

Posted by Paul G. Thompson (Member # 655) on 12-02-2003, 11:55 PM:

Mark said:

quote:
This can also cause excessive loading back on the mechanism during pull down and cause shutter bounce.

You are absolutely correct. Seen it happen.

Posted by Dick Prather (Member # 1136) on 12-05-2003, 12:48 AM:

I agree with Mark, that is the best way I have found to time most shutters. The main thing is to center the shutter adjust assembly before timing the shutter. If you don't get the timing just right you can adjust it out with the knob.

I have found some SA's as they wear have the shutter adjusting assembly become loose. The model SA pins as well as bolts the dovetail block so play adjusting doesn't work as it did on the model C/CC. The SG-100 spring wears out and the assembly starts moving while the projector is running thus causing a travel ghost. Replacing the spring usually helps. You should feel some resistance when turning the shutter adjusting knob.

I also agree with Mark on using the hardened LaVezzi vertical shaft and gear. I started using them when LaVezzi first started making them and never had one come back.

Also check that the GR-8 or newer gear at the bottom of the vertical shaft is tight and the shaft has no end play. Century vertical shafts will wear out quickly and you will get shutter shaft bounce. The spring washers as well as other parts also wear out faster. I started replacing the screw holding the GR-8 with an allen cap screw and set spring load on the vertical shaft to have the lower ball bearing cover be hard to turn by hand.

I also replace the rubber tire bracket holding the GR-234 with the model C type BR-3. I believe Century's new machines have used the old style bracket and allen screw for a few years now.

Posted by Manny Knowles (Member # 1171) on 12-05-2003, 04:32 AM:

quote:
The way I learned to time the shutter was a different way. I learned to first take the shutter blade loose from the shaft. Then advance the machine until the screw holding the intermittent flywheel is parallel with the vertical shaft. Then align the notch in the shutter blade with the pin in the sight glass.

Someone suggested that I try it this way -- it was supposedly easier -- but I then had to use the shutter knob right away to fine tune the timing.

Actually, I found that I needed to turn the knob all the way in one direction or the other and that's a sure sign of a bad timing job...actually, in those cases, the actual timing *technique* was to blame.

Needless to say, I went right back to doing it the right way:

1. Set the shutter timing knob to its midway point;
2. Set the intermittent to the pull-down midpoint and then
3. Align the shutter so that the notch is lined up with the pin -- the blade should be centred to the aperture plate.

(It's worth repeating.)

If there's a little notch or a red line on your inching knob you may want to set that up so that it indicates the position of the pulldown blade on the shutter. I usually line that up first before locking down the shutter. Does anybody else bother to do this?

Posted by Dick Prather (Member # 1136) on 12-06-2003, 12:09 AM:

Manny,
I set the notch in the up position when the flicker blade is centered over the aperture. This gives you a visual aid when the intermittent is centered in it's rest position for film threading. I set the indicator after first timing the shutter properly. I have used this method on Century and older rear shutter Simplex (E-7 and older) projectors for years.

Posted by John Westlund (Member # 913) on 12-06-2003, 12:24 AM:

Well today I timed the shutter using Marks method. Problem solved. Thanks guys [Smile]

Posted by Manny Knowles (Member # 1171) on 12-06-2003, 12:14 PM:

Dick:

Knowing the centre of the rest position would be of little value to me since I thread at the "just rested" position. I find that threading in that position gives me the best upper loop size.

I started setting the indicator like that because I didn't like the idea of it being random so I imposed some kind of order onto it. It's not critical... one could easily "eyeball" the position of the shutter blades through the sight glass.

It's interesting to know what others do with that indicator.

Posted by Mark Gulbrandsen (Member # 72) on 12-06-2003, 02:06 PM:

Threading in the "just rested" position will also result in ALOT less strain on the gear train at startup.
Mark @ CLACO

Posted by System Notices (Member # 2357) on 09-06-2006, 05:52 PM:

It has been 1005 days since the last post.

Posted by Frank Dubrois (Member # 3042) on 09-06-2006, 05:52 PM:

Having an issue with ghosting. At first I figured I could just use the fine adjustment, and usually gets rid of the problem, but upon trying that, I found that the knob doesnt work. It seems hard to turn and when we can turn it, it doesnt seem to do any good. Would the projector ghosting now have anything to do with this knob no longer working? I can retime the projector using marks method with no problem, but if we have a small ghosting issue in the future, I'd like to be able to use the knob...what would cause this to tighten up and not work?

Posted by Frank Dubrois (Member # 3042) on 09-06-2006, 11:54 PM:

Anyone?

Posted by Michael Schaffer (Member # 1204) on 09-07-2006, 12:44 AM:

Whether you have the knob on the front with the cable attached to the back of it, or mounted on a vertical shaft inside the mechanism compartment, you can turn it slowly and then you can see how it works, by slowly moving parts on the main vertical shaft assembly up or down. It is a little hard to describe in a few words, but immediately obvious when you try it. If you have the knob sticking out of the front of the projector, you may just be lucky and find that the cable is simply loose on either the end where it connects to the knob or on the other end where it connects to the compensator parts (there is a collar with a small set Allen screw in it). That may take care of the problem. If the mechanism is actually jammed, try to carefully turn the shaft that the cable connects to (or that the knob sits on, whichever applies) with a pair of pliers. Maybe it comes free. If not, you just have to visually inspect the involved parts to see if they are jammed or damaged. You may have to take the vertical shaft out and clean and/or replace some of the parts. That isn't too difficult, and the manual describes in detail how to take it out. But it does take a little feeling experience to put it back in correctly. Mark commented on that on p.1. If reassembled incorrectly, it may actually cause some damage up to snapping the vertical shaft. So if you want this done, but lack the experience, it's time for a service call to a (hopefully) experienced service company.

Posted by Frank Dubrois (Member # 3042) on 09-07-2006, 01:07 PM:

I dont remember if this knob is mounted vertically or on the front of the projector. We have a few of each. If its mounted on the front then I wouldnt have to take the vertical shaft out for any kind of repair?

Posted by Gordon McLeod (Member # 33) on 09-07-2006, 09:02 PM:

Under the circumsatnces I would call in a service engineer
I don't think you understand how the shutter compensator works and it would be best left to someone who understands it

Posted by Frank Dubrois (Member # 3042) on 09-07-2006, 09:20 PM:

your right I really dont. I didn't know it was tricky to put back in. I thought if the knob problem was easier to fix than removing the vertical shaft, I'd give it a try. But i dont like to screw with things I have no clue about. Im just not that familiar with Centurys.

Posted by Louis Bornwasser (Member # 3063) on 09-08-2006, 09:09 AM:

A goodly number of Centurys have had the adjustment shaft "locked" at the factory. Later, Strong went to a non-adjustable shutter, which I think is a GOOD thing. Fewer adjustments for little kids to play with.

The non-adjustable Century is what the original (1941) had. The shutter adjustment was added to "compete." Once again the design was pure; the salesmen changed things to compete with the non-compensated shutter designs. (E7, Super, etc.) Louis

Posted by Frank Dubrois (Member # 3042) on 09-08-2006, 05:24 PM:

They seem to like the adjustment knob and think its worth having. I know any timing or ghosting issue can be fixed almost as quickly by simply re-timing it.