This is topic Make it stop, daddy! in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Bryan Redemske (Member # 354) on 04-22-2000, 11:44 PM:
we have a problem with one of our projectors - nasty shutter ghost. really bad. ugly even.it's a century head and i'm guessing the shutter assembly is the same type - either way, it's got to be one of the first ones sold in north america.
before we tried to fix it, it was ghosting on the top half of the screen. -by the way, the gate and trap are adjusted properly - so, we took off the cover and sure enough, it wasn't lined up right. we straightened it out and ran some test film. looked good.
a couple of days ago, it started again, this time on the bottom of the screen. what the hell is going on? do we have to go take it apart once a week now?
Posted by John Walsh (Member # 168) on 04-23-2000, 12:40 AM:
Was it bent, and you "straightened it?" Or by "straightened it" do you mean you fixed it? What exactly did you do that made it work for a while?If the shutter is bent/warped, you can try to flatten it, but it should be replaced. If it is flat, and goes out of timing (ghosting) check the 2 screws holding the clamp on the shaft. Also, it may be slipping even if the screws are tight.
See that knob in the front that says, "SHUTTER?" Follow the cable down to that assembly on the main shaft; it may be loose, or something. It's kinda complicated, so just check to be sure nothing actually falling off or anything, and it doesn't slide up or down real easily. The knob should turn a screw which makes a fork-like thing go up and down.
A little more info would be nice, like the projector model letters (SA, MSA, C, etc.);do you even have a "SHUTTER" knob?; are there two shutter blades or only one; did this problem just start suddenly, or was it a growing problem; did someone leave the lamp on and warp the shutter blade....
Posted by Brad Miller (Member # 2) on 04-23-2000, 03:30 AM:
Some Century machines I've worked on do not have the shutter adjustment and rely on a bolt adjustment where the shutter control would normally lead to. Turning that bolt (it has to be loose if it is wandering) will solve your problem unless the actual shutter itself has worked it's way out of range. Obviously, that bolt needs to be tightened once it is adjusted properly. If you cannot tighten it, I recommend taking a cable tie and looping it around itself until it is just slightly larger than the head of the bolt. Then slip it over and finish tightening and snip the end off. At that point, you can remove it (don't tighten it any more) and reposition it so that the bulge of that cable tie rests up against the side of the projector, which will keep the bolt from turning. That'll keep you running until you can get a tech out there.
Posted by Scott Norwood (Member # 30) on 04-23-2000, 08:21 AM:
This is going to sound really dumb, but is the shutter screwed down tightly on the shaft?
Setting the shutter timing should be pretty simple unless there's something grossly wrong with the mechanism: set the "shutter" knob (I've never seen the bolt arrangement that Brad describes) to its center position, advance the intermittent until it just barely starts to move, loosen the shutter from the shaft and (without letting the shaft itself turn, of course) move it until it just slightly more than covers the light path, then tighten it down. Advance the intermittent a few more times to make sure that the light path is always blocked when the pulldown occurs, then replace the cover and run some film; use the "shutter" knob for fine adjustment as needed, preferably with the scope or flat/Academy lenses and plates and a pair of binoculars.
Posted by Gordon McLeod (Member # 33) on 04-23-2000, 08:42 AM:
Dumber question is someon turn the shutter timing kniob instead of the focus?
Seen that happen a few times
Also check for play in the combination of the shutter shafter and verticle shaft gear train
Posted by Jon Hudson (Member # 439) on 04-23-2000, 10:56 AM:
Brian, what auditorium number? The projector head that was on old number three was sitting on that old EPRAD/Sword crap. That projector head was always going through vertical shafts because the motor on that old setup (old setup, the serial number on that ERPAD/Sword was 000009)started up way too fast. I'm thinking that Craig never replaced the shaft when that head got moved during construction.
Posted by Bryan Redemske (Member # 354) on 04-23-2000, 12:58 PM:
jon, it's number one.okay, it's a Century SA. we loosened the screws on the shaft and tightened it back where it should have been lined up. the shutter knob doesn't do a damn thing. that's likely the next thing that gets torn apart.
Posted by Mark Gulbrandsen (Member # 72) on 04-24-2000, 05:44 PM:
The shutter knob should have at least a minor visible effect on shutter timming unless you have a huge shutter on the machine. Shutter timming knobs are not something thats really needed anyway. If you loose timming then there is usually a problem with the machine. I can't think of a european machine that has an external adjustment!!
If you are going through verticle shafts try installing one of the LaVezzi hardened stainless steel shafts. These shafts are practically indestructable, however the intermittant drive gear might still go south during the busy seasons, especially if your machine jumps to full speed in a microsecond. I've had really great luck with them overall. One thing to know is to have a barrel lap (7/16") and some medium fine compound with you as any burs, nicks or other ratty things inside the gear bores will prevent you from easily sliding them on. You will also score the new verticle shaft and it's about impossible to get a gear back off without an arbor press.
The second thing is to be sure the machine does not have a jack rabbit start up. Thats really bad for any machine no matter what brand.
Good Luck!
Mark
Posted by Gordon McLeod (Member # 33) on 04-24-2000, 08:39 PM:
Put a one ohm 300 watt resistor in serries with the motor to slow down the start up