Film-Tech Forum ARCHIVE: Vertical Jitter (SRD/CP500)

This is topic Vertical Jitter (SRD/CP500) in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Thomas King (Member # 2745) on 01-28-2005, 07:13 PM:

I've got a Vic 5 and CP500D. I've just installed a new computer in the booth for digital slides, and I put DRAS on it, to see what it did. A newish print in good condition tracks at an average error rate of 6, which seems a little high to me. The thing that DRAS complains about most is the vertical jitter, which is frequently in the red (>3 mil). The manual said that this was likely to be equipment related. What exactly is causing it? I thought it might be that the film wasn't tight enough around the sound drum, but I see no way of getting it any tighter. I tried shifting back and forth a few sprockets, but that just changed the size of the loop under the gate, without changing the jitter rate on the display.

Any suggestions that anyone has would be gratefully appreciated.

Posted by Gordon McLeod (Member # 33) on 01-28-2005, 07:53 PM:

What you don't say is if you have a basement or a penthouse reader
If it is the basment style check the scnnaer bearings and the rollers also the damper
the vic 5 basement usually tracks very well

Posted by Thomas King (Member # 2745) on 01-28-2005, 08:09 PM:

Sorry, I forgot about that. It's a basement reader, mounted just above the exciter lamp house. I've checked the rollers that press down on the rims of the sound drum; they're fine. I'm wondering that perhaps it might be a side effect of the tensioning device that's mounted after the sound drum; instead of the hydraulic dash pot that seems to be standard, there's a manky little sprung roller assembly. It looks cheap and unfunctional.

Posted by Gordon McLeod (Member # 33) on 01-28-2005, 09:06 PM:

The cinemecanica sound head often had the dashpot damper as an option so maybe someone did a home brew

Posted by Pete Naples (Member # 761) on 01-29-2005, 05:59 AM:

The spring type is far more common than the hydraulic here. Check that the lay on rollers and their pivots assembly haven't siezed up, also when did anyone last oil the scan drum bearings (Assuming it's the older type with the oil point?)

Also check the slip clutch asembly on the back of the draum shaft, at the flywheel end, common source of wow and flutter!

Posted by Matt Zeiner (Member # 1914) on 01-29-2005, 08:58 AM:

Sounds a bit out there, but I have seen several V-5's with mechanical oscillations causing excessive jitter in the original basement reader with the lightpipe and remote mounted exciter lamp. One or both of the belts may be too tight/ too loose, setting up an oscillation. If you have a scope, you can see the jitter on the right-hand "goalpost." Tension adjustments to both belts have helped in this case. Try it.

Posted by Gordon McLeod (Member # 33) on 01-29-2005, 11:19 AM:

post a pix as i havent seen the spring type

Posted by Richard Fowler (Member # 893) on 01-29-2005, 11:51 AM:

Most of the V-5 units I worked had the cheaper double roller on a spring dampen pivot arm. Ouside of what Pete and Gordon have noted is that you can also get jitter if the outer bell of the sound drum has been removed for service or cleaning and properly not seated when remounted. I have also seen problems when people have dropped the end bell on the floor and distorted the film riding edge.

Posted by John McConnel (Member # 2000) on 01-30-2005, 01:23 PM:

To digress momentarily from the subject, who makes a Dolby Digital basement reader for a V-5? Thanks.

Posted by Gordon McLeod (Member # 33) on 01-30-2005, 03:25 PM:

funny cinemecanica does [Smile]

Posted by Thomas King (Member # 2745) on 01-30-2005, 06:10 PM:

Pete: I couldn't see any sign of the slip-clutch you mentioned, all there is under the flywheel cover is a bigish flywheel.

I dismantled and throughly cleaned the lay-on roller assembly (which was really horribly sticky). It seems to have made some difference: tonight's film ran through keeping the tensioner about a mil from the stop position, which was an improvment. I'll run some SRD film through to look at the jitter.

I'm just wondering: how does one go about lubricating the sound drum shaft? I can't see any way to get to the bearings.

Posted by Monte L Fullmer (Member # 2797) on 01-30-2005, 08:22 PM:

quote: Thomas King
just wondering: how does one go about lubricating the sound drum shaft? I can't see any way to get to the bearings.

Across the shaft cover, being the housing, there should be a dimple looking device at the middle. This is where you take a small oil can, press down the dimple ball and this let's oil down to reach the end bearings.

Cine V-5's had to have this area oiled on a regular basis, or situations like this arises due to the simplified soundhead version of the V-5's. For the simplified version do not have roller bearings, but just sleeve bearings on each end.

-Monte

Posted by Dan Harris (Member # 1759) on 02-01-2005, 04:59 PM:

Gordon, for info here is a (brand new) Vic 5 with spring dampened roller assembly. Oh, and basement SRD reader too!

Posted by Gordon McLeod (Member # 33) on 02-01-2005, 05:02 PM:

Interesting is that factory or an add on?
All I have ever worked with had the hydraulic damper

Posted by Richard Fowler (Member # 893) on 02-01-2005, 05:29 PM:

The spring damper is mounted on a plate which has holes to match the mounting screw holes normally used for the oil dash pot damper.

Posted by Thomas King (Member # 2745) on 02-01-2005, 06:12 PM:

Dan: thanks for posting a picture, that's almost identical to my machine, only slightly newer! (I have no idea where my camera is).

I can't find how to lubricate the sound drum bearing assembly. I've examined the shaft cover, but all that's on it are the two securing hexnuts; I can't find the dimple ball that Monte mentioned. Does anyone have a picture of it?

Posted by Dan Harris (Member # 1759) on 02-02-2005, 04:12 AM:

quote: Gordon McLeod
Interesting is that factory or an add on?

These are brand new direct from the factory, awaiting installation. The manual has maintenance diagrams for this and a dashpot so I expect you can specify which you want.

I've never worked on a Vic 5 with a dashpot on this side of the pond, but from my time on Vic 9's I remember them to be more substantial that the spring assembly.

Posted by Pete Naples (Member # 761) on 02-02-2005, 03:03 PM:

Thomas, not all V5s have the dimple for shaft oiling, so yours may not have it. I don't know if they all have the slip clutch, it looks like a four fingered springy washer, between the flywheel and the end of the shaft. I've seen these weaken and wear out so the flywheel is slipping with respect to the drum/shaft. Ironic as it's purpose is to allow slip while the drum comes up to speed.

Gord, that's how the bulk of V5s in this country are set up, at least the ones I've seen supplied/installed by SA. I'm servicing 12 this week supplied/installed by Robell Sound, these have the hydraulic damper, a la V8, V9. Also I've yet to see one with the much talked about curved gate, even brand new.

What is it with the basement readers? You have to slide the lamphouse back to gain access to the lateral adjustment screws, which then don't allow enough movement to correctly align the blasted thing! Sometimes I've had to shim the whole assembly out from the casting, this one I was working on today, there were no shims and I couldn't get the CCD board moved far enough towards the projector, which suggests that the film path alignment through the sound head as a whole is off, but how the heck would you adjust that?!

Posted by Richard Fowler (Member # 893) on 02-02-2005, 04:00 PM:

Been there, done that....in addition to an occaisonal shim which Cinemeccanica will supply, we have had to enlarge the circuit card mounting holes in rare instances. Most of the V-5 especially if they have the factory basement reader are going to have the 5V705 sound drum casting which has ball bearings instead of the need to oil sleeve set up. The "simplified" oil type drum set up was more common on the older projectors such as a V-4. The spring damper is several hundred$$$ cheaper than the oil dashpot and I found there was less chance of film scratches that the oil dashpot is capable of doing if you did not keep the tiny film path rollers clean and lubricated.

Posted by Thomas King (Member # 2745) on 02-02-2005, 09:03 PM:

Pete: That's a clutch? I thought that was just a sprung clamp! How much slip should it have? As far as I can tell, it's only held in by a screw, and if I undo it, it'll just become really lose. At the moment there's no slip; probably not too much of a problem as it takes 5 seconds to ramp up. And do you want some dashpot oil? Everytime someone orders spares for out projector, they order it; despite the fact we don't have a dashpot [Smile]

I should really get SA back to service the whole lot, but I really can't afford it.

If it's not possible for me to lubricate the sound drum shaft; can I assume that I don't need to, or do I need to dismantle it some more?

Posted by Pete Naples (Member # 761) on 02-03-2005, 03:48 AM:

Yes that wee spring device is a clutch of sorts, a crude one. It shouldnt' slip much at all, my point is that if it slips too much you won't get good smoothing from the flywheel. I've also had problems with them in the past due to wear on the sprung grounding plate ( I assume it's there for anti static grounding purposes ) that resides inside the flywheel cover, on one very early Vic 5 up here it had disintegrated and the bits were rubbing between the flywheel and the cover, causing issues.

No, if there's no oiling point on the shaft housing don't oil it!

There are other companies & people equally, if not more capable of servicing your Vic 5, probably cheaper too! Contrary to popular misconception it's not rocket science....

Posted by Paul Carey (Member # 2241) on 02-03-2005, 10:47 AM:

Be careful if your messing about with the cross shaped spring/clutch clip on the flywheel. I snapped one when trying to bend it back to the correct shape after we had problems one of our vic 5's. Last time, many years ago now, we had a problem with analogue sound being warbled, a quick change of the sound drum bearings and a new spring on the fly wheel and we were back in business. so you never know, it could be something similar.

Posted by Thomas King (Member # 2745) on 02-03-2005, 11:23 AM:

I think I'll avoid fiddling with it until I'm sure I need to [Smile]

My main problem at the moment, when the feature's running, the tensioning device isn't actually being used: it stays on its stop. Is this normal? When running a feature, what sort of clerance between the stop post and the tensioning block is common?