Film-Tech Forum ARCHIVE: Christie Sound Problem

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Posted by Don Sneed (Member # 955) on 07-09-2006, 02:26 AM:

I have (2) Christie machines, 5-years old doing the same thing..a garble sound (like if the voices is underwater)..Sound Drums bearings was changed (2) yrs ago, found no problem with the bearings, sound drum turns as normal when film leaves machine.. Found upper sound roller arm assy. is bouncing rapidly, Replaced upper & lower sound rollers w/bearings, airpot, center sprocket assy. Belts are OK...no change!! roller still bouncing...this is a 12-plex, all other machines has no bounce in upper sound roller assy.... Any ideas on what to do next, or has anyone had this problem before ?? I am out of ideas, changed all parts that can be related to the bounce..any ideas ??

Posted by Darryl Spicer (Member # 711) on 07-09-2006, 02:30 AM:

Have you changed the two projector drive belts. Don't know if that would cause the problem but may be worth a shot if they have not been replaced in a while. Woops I just read where you said they were ok but maybe you should try changing them.

Posted by Dustin Mitchell (Member # 372) on 07-09-2006, 03:13 AM:

How do you load the sound heads? Do you set the film on the lower constant speed assembly will holding the guide rollers against the sound drum and then tighten by two sprockets (so the guide rollers are 'floating' off the sound drum)? If so, instead of tightening by 2 LOSEN by 2. I personally have no idea why but that should fix it (have had the exact same problem on one of our Christies for years with several techs unable to solve it other than by this method.

Posted by Don Sneed (Member # 955) on 07-09-2006, 03:30 AM:

Dustin..they are theading with two sprocket holes pulled...they have no digital sound in these houses so analog only...pulling two sprocket holes or pulling one sprocket hole...no change, still have bounce...with roller arm bouncing, sound is garble or wobbling...only way to stop & sound normal or near normal is to not float the rollers...

Posted by Brad Miller (Member # 2) on 07-09-2006, 04:27 AM:

Are you aware the airpot can be fine tuned via the screw at the bottom? That sounds like the majority of the problem (coupled with not-quite-good bearings.)

When troubleshooting these machines over the phone, I would have the projectionist check for bad bearings by threading with 0 perforations, then loosen up one perf, start the motor and watch it run (with a roll of film, not a loop). If the slack above the sound drum is stationary, it's not the bearings and is probably related to the airpot. If the slack above the sound drum gets smaller then larger then smaller then larget you have bad bearings. That'll at least tell you what parts to get.

(BTW, just because the bearings seem to spin free doesn't mean they don't need to be changed. Just something quirky about those P35GPs.)

Posted by Richard Hamilton (Member # 321) on 07-09-2006, 04:52 AM:

Don,
Why were the bearings replaced 2 years ago? Could be that Christie changed suppliers and those bearings were in the top of there parts bin when they sent them and they are a lower quality bearing. I ran into this with a megasystems machine. For some reason, Ballantyne changed suppliers, and I had some problems, when I compared them to different bearings (same part number) in inventory at Ballantyne, they were different.

Rick

Posted by Mark Gulbrandsen (Member # 72) on 07-09-2006, 08:44 AM:

Rick,
Even though you have Ballantyne ties... never get your bearings from Ballantyne... they typically stock the lowest grade of asian bearings made. I quit getting bearings from them 15 years ago and my re-curring bearing problems on 5 Stars and Ballantynes went away! If at all possible on a belt driven shaft as in the Mega Mother and except for sound scanners use bearings with rubber seals as they will last way longer... that black belt crap won't get into the bearing and and cause pre-mature failure.

Don,

You have something very definately worn out in there and probably something that is worn in the film feed path but before the sound head. Since the upper dancer is pulling back upwards check the center feed sprocket assy in particuluar to see if it spins freely. I had a similar problem in Jackson once and the center feed sprocket bearings had failed causing very rough film motion. You couldn't detect this when turning the machine over by hand but remove the belts and spin all the shafts and stuff and you will likely find the culprit if its is that.

I've also had alot of the dancer arm bearings fail. They are tiny beaings for the job, just shielded not sealed and spin at a relatively high speed. They can be removed from the dancer rollers for replacement but with quite some difficulty in the booth so you might want to just get the roller with bearings if thats needed.

The dashpots do wear out on these machines. They can get to a point where they cannot be adjusted to give any damping action at all, The dashpot on the Dolby 700 and 701 scanners is almost identical and I've also had to replace several of those in the past couple of years!. Also check to see if the damper piston rod is broken. If you check and this soundhead does not have a travel limit stopper for the upper dancer arm then that is what you will likely find. I've had alot of piston rods break and its always because there is no travel lmit stopper. Sometimes the broken piston rod hangs down inside the dashpot making it hard to see that its actually broken. If this is the case when you replace the dashpot be sure to also get or makeup some of the travel limiter stops. This is a relatively easy part to make in the shop and instsll that on the projector... and any others in the booth that don't have them. Gobs of P-35's left the factory without these stoppers. Also setting that new dashpot is best done with a W&F Meter and SMPTE Flutter film. If you have a meter but no film (good luck getting W&F from SMPTE) call NT-AV and they will make it for you. Setting up one of these soundheads this way is very revealing as to just how bad the P-35 flutter is even when everything is working normally.... you might get it as low as 1% but probably more like a bit over 2% and it depends on belt tension and some other adjustments to get it that low!

The new Cine-X35 has excellent W&F specs, better than a Simplex or Century becasue they went to round tooth timming belts and scrappeed the dounble sided belt completely. Basement digital on these machines works great! Ditto for the early Christies that have the shutter gear box... they also have very low W&F.

Hope some of this helps.....

Mark

Posted by Richard Hamilton (Member # 321) on 07-09-2006, 11:15 AM:

quote: Mark Gulbrandsen
Even though you have Ballantyne ties... never get your bearings from Ballantyne... they typically stock the lowest grade of asian bearings made. I quit getting bearings from them 15 years ago and my re-curring bearing problems on 5 Stars and Ballantynes went away! If at all possible on a belt driven shaft as in the Mega Mother and except for sound scanners use bearings with rubber seals as they will last way longer... that black belt crap won't get into the bearing and and cause pre-mature failure.

You saying Ballantyne projectors are commies? [Big Grin]

Did you ever actually work on the "Mega Mother" as you put it? I had one instance of failure, and I simply make a suggestion for Don to look at. Maybe Christie stocks the best bearings just like you do? Since I have ties with Ballantyne, I will e-mail them this link and make sure they don't supply you any parts because you made a comment never to buy something from them. [evil]

Mark, in this case, the bearing was supposed to have the rubber seals. Somehow, they didn't. It was a totally different bearing that was put into the same stock as the correct ones. I had to make a trip back and change every one of the bearings, even though I got replacements when it happened in China. Luckily the failure happenned before opening day of the amusement park, and I got them back up and running.

Posted by Mark Gulbrandsen (Member # 72) on 07-09-2006, 11:34 AM:

quote: Richard Hamilton
Did you ever actually work on the "Mega Mother" as you put it? I had one instance of failure, and I simply make a suggestion for Don to look at.

No, have seen more than enough though... I wouldn't touch one with a 10 foot pole. Its a genuine Rube Goldberg machine from the ground up... as poorly executed as something gets. However... The dual intermittent is a great idea and a vaild patent, just built by the wrong company. Shoulda been a Kinoton built machine! I think everyone here and everyone at Strong already knows my opinion. Give me a much more light efficient Linear loop, a Kinoton or Ballantyne machine for 8/70 any day over the Mega mother.

Well, I'm glad that you finally at least admit they are Commies!

FYI: Christie did not use bearings with rubber seals on the P-35 GP's early in production, instead they also used cheapo bearings that had fibre or fiberglas shields on them and they paid the price for that. Today all the belt related bearings in a Christie have rubber seals on them to keep the belt shavings and black crud out of them. Don't forget that its VERY dry and dusty in this area and as a result this area is an acid test for almost any ball bearing. Other than those early Christies I've had more bearing failures in 5-star sound heads than any other piece of projection gear period, next in line would be bearing failures in Simplex's starting with the 1060's and later machines, usually the lower vert. shaft bearing and sometimes in the compensator, gee... someone assembling machines at Strong used to leave the grease shields on keeping the libricating oil out [Big Grin]

. I don't know what it is about those bearings used in the 5 stars, perhaps lousy grease in them or something but all my problems ceased when I stopped getting them from Strong. In fact I don't think we get any bearings from Strong. As a dealer Strong's parts prices alot of the time are consoderably higher than another source and we get alot of our replacement Strong parts from that other industry source that has alot lower prices. Compare Strongs dealer cost on the Ballantyne Star and cam with LaVezzi's cost for instance....

Yep! With bearings I can give our customers a higher grade of bearing for the same or less than our cost from Strong. Keep in mind that we get the highest discounted price from two of our local bearing distributers so I am more likely to at least use ABEC 5 bearings instead of the cheap stuff. So if you have some objection to me using higher grade bearings in my customers equipment please let me know the reason.

As for Strong's bearings being Commie bearings I don't use them and wouldn't know but I'd bet that you'd be able to tell us. I probably get some commie bearings now and then from beairing houses and never even know it. The Commies also make some good equipment just like everyone else does, I don't mind their high quality products at all, they can be very good. I just don't trust the Commies themselves.

Mark
P.S. FYI: Alot of Christie's equipment is also Commie [Big Grin]

Posted by Brad Miller (Member # 2) on 07-09-2006, 03:49 PM:

quote:
Also check to see if the damper piston rod is broken. I've had alot of piston rods break and its always because there is no travel lmit stopper.

Mark, you don't need the stopper. When installing a new airpot, simply snip off a tiny amount (about 1/8 inch) of the rod. This way the airpot can no longer bottom out, which breaks the rod. Problem solved.

Posted by Mark Gulbrandsen (Member # 72) on 07-09-2006, 05:26 PM:

Yea, I agree Brad and I normally do that to them. All the machines around here have the stopers on them and I don't see why not to put them back on, may save something in a bad pile up. Also, its easier to put on a stopper than it is to remove an existing dashpot to snip off the shaft... That was mainly what I was thinking on his behalf if the other machines dashpots are bottoming out. It takes about 30 seconds to install a stopper but who knows how long to remove the dashpot and modify... depends to some extent on how dirty is is on the backside.

Mark

Posted by Monte L Fullmer (Member # 2797) on 07-09-2006, 06:00 PM:

Hmm...garble sound - is the impedence drum flywheel brushing againt the back cover by having the flywheel installed to far out on the drumshaft-in which I've done that before on accident?

Yea, snipping a bit of the shafts of the airpot works quite well...

-Monte

Posted by Charles Greenlee (Member # 3856) on 07-13-2006, 11:18 PM:

Yeah, we've had that before too. Somehow the flyweheel slid out on it's shaft and started rubbing the cover. Everything else seemed fine, finally I looked at the cover and noticed that the rubber was worn where the flywheel was. The flywheel was tight, so I don't know how it slid, but it was easy work to back the set screw out some and slide the wheel back on right, and resecure everything.