Century JJ (Occasional "knocking" sound)

[Ryan Gallagher]

For clarity on the 70 conversion. It is possible to remove the upper 35mm pad roller without putting a 70mm one in it’s place?

70mm is a month away still but we do not have spare 70mm pad rollers that I have seen.

[Mark Gulbrandsen]

Tony, I never had anything like that happen to a Century, but I have seen other strange stuff happen that is no fault of the projector. If you had rust in an intermittent, you obviously had contaminated oil that got put in the intermittent. I used to service a theater in Chicago where a disgruntled projectionist put battery acid on the gear train. That also caused a big orange, rusty mess, and everything had to be replaced on the gear side. Even the intermittent drive gear and cam had to be replaced. I installed a loaner SA and did the rebuild in my shop.

[Tony Bandiera Jr]

Thanks Mark & Brad. I did an oil change on the intermittent too finally (in place). What came out did not look as dirty/dark as I was expecting, I think it is just the window/casing on that one that makes it seem darker. I did not have anything to flush with handy so will do that another day. But it does sound improved now. Maybe slightly perceptible without film, but with a loop running you can't detect it over the projector noise anymore (or at least couldn't in my short tests).

I did check that the intermittent does not have play in any of the lock positions. And it feels reasonably smooth by hand, though I'm sure i've never felt a perfect one. Will definitely keep an eye on it. Found some older videos in the archive and it definitely doesn't sound that awful yet. I was listening with the back covers off too, it didn't sound like it was shutter shaft side but will definitely stay vigilant.

Never flush an intermittent with anything other than clean oil!!

Be aware that with Century movements, if you see bronze or rust colors in that window rebuild or replace that movement immediately. At a theater I used to work at, our JJ started leaking oil. Then the leak got worse and the noise got a bit louder. We used to have to refill the oil TWICE daily! But the cheap (and stupid) manager refused to order up a replacement...until after it locked up, Saturday night, full house (around 600 people). The carnage was considerable: two stripped gears, about 500 feet of the print shredded, a burned up motor, 600 refunds, five lost shows....and the tech and replacement had to be flown in on a charter jet flight. My best guess is that $2,000 intermittent ended up costing the theatre well over $12,000 to replace! (i was not the projectionist on shift when it happened (I had moved on to another job)..the asst. manager (a friend) called me in delight. I called that former manager to rub his nose in it..when he hung up on me, I went to the theatre, bought a ticket to a movie and badgered him in person. I left when he threatened to call Paul Blart the mall cop on me. Best "I told you so!" EVER!

[Jim Cassedy]

<edited> Also those loops are too darn big.. Also you MUST remove the 35mm
pad roller from the upper loop when running 70mm so you don't put "train track"
(aka: "JJ scratches") on the print.

Earlier this week I ran a 35mm print of a repertory title that was pretty much in "like new"
condition. (ie:never been platterized, zero splices in all 5 reels) EXCEPT all of Reel 4 had
these intermittent light 'scuff marks' on the emulsion side, which look like somebody made a
loop a little too big (or small) at some point. Since they didn't gouge the emulsion, they were
invisible on screen, unless you were really looking for them. But it could have been worse!


LoopScratch.jpg

Brad, as always, gives good advice about removing the 35mm upper loop pad rollers for 70mm.
I didn't always do that, until one time I got a print that had been scratched by somebody not doing
that, and I didn't want to be responsible for causing that type of damage to any print I handled.
Fortunately, in our spare parts bin, we had some extra 70mm rollers, so now I take the 35mm rollers
out and put in the 70mm ones. Brad told me there is a slight difference in size in some of the 70mm
rollers (he can elaborate more on that) but I guess I got lucky because I didn't have the problem
with the spare rollers we had in the booth.

[Ryan Gallagher]

Sometimes, on Century's, the knocking noise can be caused by the long shutter shaft bobbing back and forth on occasion. It's almost always caused by another gear, bearing, or both failing. If not tended too, then a new shutter shaft will also be needed. That long shaft is spring loaded to allow a slight lateral movement on start up of the projector, to relieve stress on the shutter gear. So keep an eye on it!!

Thanks Mark & Brad. I did an oil change on the intermittent too finally (in place). What came out did not look as dirty/dark as I was expecting, I think it is just the window/casing on that one that makes it seem darker. I did not have anything to flush with handy so will do that another day. But it does sound improved now. Maybe slightly perceptible without film, but with a loop running you can't detect it over the projector noise anymore (or at least couldn't in my short tests).

I did check that the intermittent does not have play in any of the lock positions. And it feels reasonably smooth by hand, though I'm sure i've never felt a perfect one. Will definitely keep an eye on it. Found some older videos in the archive and it definitely doesn't sound that awful yet. I was listening with the back covers off too, it didn't sound like it was shutter shaft side but will definitely stay vigilant.

[Mark Gulbrandsen]

Sometimes, on Century's, the knocking noise can be caused by the long shutter shaft bobbing back and forth on occasion. It's almost always caused by another gear, bearing, or both failing. If not tended too, then a new shutter shaft will also be needed. That long shaft is spring loaded to allow a slight lateral movement on start up of the projector, to relieve stress on the shutter gear. So keep an eye on it!!

[Ryan Gallagher]

Can confirm, the noise does occur without film running.
Brushed some grease on the drive side, gearing. Re-oiled the starwheel and upper and lower drive shafts. Noise is still present. Not as pronounced without film though.

Listening closely without all the fans and projectors running in the booth it appears to originate at the intermittent. Will upload another video/audio tonight.

Seems like flushing and putting fresh oil in that intermittent would be next thing to try. Definitely overdue but lube may not be a solution. My only sign of encouragement on that front is initially it does not do it, only after it's been running for 30 seconds or so does it start.

[Ryan Gallagher]

I’ll try without film tomorrow. Cheers on the loop size, we had a guest projectionist that night and that is his normal JJ mode.

This unit has a sweet spot where it “purrs” depending on loop size. He might have been outside of that but it does seem to prefer larger loops from an acoustic standpoint,

[Brad Miller]

That click doesn't sound quite like I was expecting to hear. The camera microphone may be making it sound a little different, not sure.

Does it make those clicking noises if you run the projector without film?

Also those loops are too darn big. 35mm is somewhat forgiving, but when you run 70mm you need to make them WAY smaller. Also you MUST remove the 35mm pad roller from the upper loop when running 70mm so you don't put "train track" (aka: "JJ scratches") on the print.

[Ryan Gallagher]

Amusing aside, the projected image appears red because it WAS. They opted to show a VERY red/magenta print. Was Austin Film Society's call, not us, and they show lower quality prints all the time at their space.

That print also had sprocket teeth tracks through the frame for like 12 feet in two places on R2, only 30 splices (excluding heads/tails), but the prior repairs held. We went back and forth a lot about whether to risk more damage on this one as we had a perfectly good blu-ray backup. Programmers went for it, described the print itself as a little "punk rock" during the intro. LOL

[Ryan Gallagher]

I feel like this is a new sound on this JJ, or was more pronounced with this 40 year old print (Archive Print 2 of Ladies and Gentlemen The Fabulous Stains, But 16B on the paper loops).

It is a bit hard to make out in this video, but there is an occasional "knock knock" sound coming from somewhere other than the gate/loops. I think the most audible ones in the video are right at the beginning, but if you listen closely you can hear them. More obvious in person. Any guesses? Slop somewhere in gear meshing... not enough lube somewhere? Or a worn part? Intermittent has plenty of oil but this is also the unit that needs an oil change, it doesn't leak at all and therefore the oil it has hung onto has darkened in color. Grease has been refreshed recently on the drive side, but maybe it needs a re-application.

On that front, do you recommend pulling the intermittent for draining/flushing. Or try to do it in place?

YT Unlisted Link: https://www.youtube.com/watch?v=vEjji-u5vms