Film-Tech Forum ARCHIVE: Century C shutter "ghosting" Adjustments

This is topic Century C shutter "ghosting" Adjustments in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Mark Farr-Nash (Member # 4233) on 09-08-2007, 03:00 PM:

Hey guys,

I recently replaced the intermittent in my Century C projector, so that mine can be repaired. I've re-timed and re-re-timed the shutter, and spin the knob in both directions, but I still seem to have an irregular streak or ghost from time to time. It was bad last night, so I cracked the case open and re-timed it (yet again) today. Now it's running fine with the test loop, but I have a sneaky suspicion that I'll have a ghost later.

My first thought is that the screws are no longer gripping the shaft and causing the shutter to slide over time. I can certainly get new screws to drop in, but is there maybe something else I'm overlooking?

Thanks in advance,

Mark

Posted by Louis Bornwasser (Member # 3063) on 09-08-2007, 03:50 PM:

If you are getting a true streak, then timing is your trouble. If you get an occasional up or down streak at random, then you may have a shutter bearing going bad. Even new bearings do not always help, since the newer bearings are very very intolerant of end loading and out-of-trueness. (being lined up precisely.) Louis

Posted by Mark Farr-Nash (Member # 4233) on 09-08-2007, 04:50 PM:

Well, I just started the film up and bingo, the movie was a streak-fest. I adjusted it as much as it would go, to a mere ghost, but at this point, it's pretty steady. I don't think it's a bearing problem. But could it also be related to the movement of the intermittent? I may have replaced a dud with a dud.

Mark

Posted by Louis Bornwasser (Member # 3063) on 09-08-2007, 05:32 PM:

Remember the knob will not adjust the shutter unless it is within range. Center the shutter knob. Loosen the shutter hub. Slowly turn 2 intermittent teeth down. Retighten hub after centering the blade, completely closed. It is important not to turn the shutter shaft when moving the shutter hub. Hold it firmly in one hand while rotating the shutter. Louis

Posted by Mark Farr-Nash (Member # 4233) on 09-08-2007, 06:19 PM:

I'm gonna go re-adjust it now. Thanks, Louis. I'll report back soon.

Mark

UPDATE:

Okay, with careful re-adjusting of the shutter, centering the knob, and lots of careful back and forth, I have reduced the streakfest to an irregular up or down streak. Picture is good for about thirty seconds, then a blip of streak appears either at the top or bottom. The knob won't correct it, because when it's clear, it's clear.

If the problem isn't the intermittent itself, then could it be the bearings?

Mark

[ 09-08-2007, 08:11 PM: Message edited by: Mark Farr-Nash ]

Posted by John Hawkinson (Member # 1135) on 09-08-2007, 10:48 PM:

Sometimes the fire shutter can interfere with the image in a way that looks kind of like travel ghost. Try making sure it's all the way up. Also, looking at the the image in the port glass can often help you get a better understanding of these these problems.

--jhawk

Posted by Daryl C. W. O'Shea (Member # 1303) on 09-09-2007, 02:50 AM:

Do one of the shutter blades have a small crack in them (located in the blade where it passes the aperture)?

Posted by Scott Balko (Member # 438) on 09-09-2007, 08:55 AM:

How much play is in the entire gear train? When you turn the motor flywheel back and forth by hand, how far can you go before everything hooks up? Do you have a sloppy gear pin or something that changes the position of the shudder to the intermittant in varying amounts depending on load? All the gears are helical so if a gear fits nicely on the shaft, but can move along the length of the shaft a little bit, it can change the timing in either direction.

Posted by Tim Reed (Member # 137) on 09-09-2007, 11:17 AM:

Scott's on the right track. I'd check the "intermediate" gear. This is the long fat gear on the vertical shaft that actually drives the intermittent movement. Check to make sure its retaining collar on the top hasn't come loose, or that the gear's not missing teeth. The slot and/or driving key can also become worn on this gear and can cause flashes of travel ghost.

Also, check your shutter shaft for proper tension and clearance to the vertical shaft shutter drive gear. There should be just a slightly-perceptible back lash in the gear mesh, and the shaft should not "bounce" when running.

I think you'll find your problem in one of these areas.

Posted by Mark Farr-Nash (Member # 4233) on 09-09-2007, 02:46 PM:

Okay, I checked the drive shafts, and I could indeed detect a noticeable movement (is it bouncing if it moves horizontally) along the horizontal shaft that is connected to the shutter. It moves the shutter closer and farther away in a slightly irregular pattern. My other projector doesn't have that movement on the shaft.

I checked the gears out and they appear to have all of their teeth. I checked the play by turning the intermittent by hand and found that the teeth immediately engage.

Could it be the shaft, then, that's causing my problems?

Mark

Posted by Louis Bornwasser (Member # 3063) on 09-09-2007, 06:51 PM:

There is a spring load on that shaft. If bearings are OK, then tighten up the spring load. If the spring load is already OK, then small hang ups in the bearings will translate into a "bump" of the shaft from front to back. Louis

Posted by Mark Gulbrandsen (Member # 72) on 09-09-2007, 09:29 PM:

Its also a good idea to check that the shutter loading spring does not suffer from compression set... after decades of being under compresson many of them do. Just compare it to a new spring side by side....

Mark

Posted by Steve Guttag (Member # 268) on 09-10-2007, 09:31 AM:

I've had shutter timing issues when the hub of a gear is slipping within the fibre gear too. Mind you it isn't like it is slipping sloppy loose but enough that the stress of start up will cause it to rotate slightly.

Note, the shutter shaft bouncing is an indicator of ANYTHING in the gear train being amiss. Being the fastest spinning thing in the projector (with relatively low mass), it will show off any instability.

Steve

Posted by Mark Gulbrandsen (Member # 72) on 09-11-2007, 05:58 PM:

quote: Steve Guttag
I've had shutter timing issues when the hub of a gear is slipping within the fibre gear too.

I've only had this happen on Simplex X-L's.

Mark

Posted by Steve Wilson (Member # 2411) on 09-11-2007, 07:57 PM:

I was having this kind of trouble back in the spring and my problem was a warped drive-In shutter blade. Louis sold me a New one and problem was fixed. Of course, you may have another problem. Found the solution to my problem right here with the good buddie of Film Tech.

Posted by Monte L Fullmer (Member # 2797) on 09-12-2007, 04:11 AM:

..would his intermittent assembly not be set to the proper clearance where there is too much gearplay between the drive and driven gears?

Posted by Mark Gulbrandsen (Member # 72) on 09-12-2007, 08:39 AM:

quote: Monte L Fullmer
..would his intermittent assembly not be set to the proper clearance where there is too much gearplay between the drive and driven gears?

I have one today here in Billings that I have to rebuild that someone didn't set the intermittent into the drive ear teeth properly.... as a result half of each tooth is worn away.

Mark

Posted by Mark Farr-Nash (Member # 4233) on 09-12-2007, 09:10 AM:

Final verdict: I just had my tech out here, and he replaced the entire vertical shaft (which was causing movement all along the train), and replaced one of the gears which had been worn down. Now it runs like a top. There was about a half an inch, total, of slack and play in the whole assembly.

Thanks guys, for pointing me in the right direction.