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Topic: Platter takeup problem

Joe Grace
Film Handler

Posts: 44
From: Maine
Registered: Feb 2000

posted 12-24-2000 12:31 PM

The platter is a Christie 5 deck model. There is a lot of space between the platter and the projector. For some reason during the last couple of days when I start the film the failsafes drop and everything shuts off, this does not just happen on one deck. It is like the film is heavier or something, because there is little takeup tension. Does this have something to do with the weather (colder, drier)? Would ordering a new spring for the return arm help? Or is there a way to tighten the return arm spring? Thanks for any help.

Joe

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-24-2000 02:07 PM

Sounds like the motors arn't accelerating fast enough to keep the film tight

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Brad Miller
Administrator

Posts: 17775
From: Plano, TX (36.2 miles NW of Rockwall)
Registered: May 99

posted 12-24-2000 02:26 PM

I've ran film 100 feet over many rollers onto a Christie platter before for takeup with no problems. I highly doubt it has anything to do with something mechanical. When the motors are cold, frequently they cannot reach maximum speed in that 1/4 second that they have to "get going" at the start of a show. Many operators warm up their platters by holding the takeup arm so the platter will spin several times. A simple re-timing of the platters always does the trick, though.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 12-24-2000 02:43 PM

Joe, I totally agree with Brad. Retime your machine to specifications and your problem will probably go away.

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Joe Grace
Film Handler

Posts: 44
From: Maine
Registered: Feb 2000

posted 12-24-2000 02:55 PM

I will try re-timeing and running the platter for a while before it is used, and see how that goes. Thanks for the tips!

Joe

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Darryl Spicer
Film God

Posts: 3250
From: Lexington, KY, USA
Registered: Dec 2000

posted 12-24-2000 08:17 PM

If you are not already doing this try it. after threading the machine backup the takeup platter until you feel the moter try to start. This will allow the platter to start right up at the same speed as the projector. if you allow the takeup arm to be in a further position from the start point the projector will be at full speed and can cause the arm to pass the start point before the platter is up to speed. Causing the arm to reach the stop point dumping film into the floor.

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 12-24-2000 08:43 PM

Here is something else to check, since your problem involves more than one platter:

Check your line voltage. If it is 105 VAC or less, the platter may not function properly. This could be aggravated by fast-start projectors. If you try to retime your platters and you find you can't get 25 rpm out of them, I'll almost bet your line voltage is too low.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-26-2000 05:38 PM

If retimming doesn't work
put a 100 ohm 300 watt wirewound resistor in serries with the simplex motor to slow down the start up

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 12-27-2000 12:10 AM

Joe, I talked with another service tech, and he pointed out to me that a Zener Doide is in the circuit that sets the entire reference for all of your decks on that machine. He indicated that if this diode is starting to fail, it may give the indication you described. Gordon, I respectfully disagree with the size of the resistor in series with the motor. Because of the high starting current, most of the line voltage would be dropped across that resistor. I doubt if the motor would even start. However, As you pointed out, a high power wire wound resistor would work, but its selected resistance value would depend upon the starting and running current of that motor. Then, one has to be careful not to starve the motor. If the motor is starved, magnetic slip will occur, and the motor will burn up.

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Rory Burke
Expert Film Handler

Posts: 181
From: Burbank, CA, USA
Registered: Jun 2000

posted 12-27-2000 03:34 AM

hmmmmmmm....Christie platters? timming timming timming why does it seem Christie platters are contantly being timmed...Does anyone out there also find that staying ontop of Chrisite platters by timming them keeps the headaches <service calls> from reoccurring as often?

Rory

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Randy Stankey
Film God

Posts: 6539
From: Erie, Pennsylvania
Registered: Jun 99

posted 12-27-2000 09:03 AM

It depends on what payout control system you have in your platter. (Christie AW-3)

If you have the Photocell kind you are going to be spending a lot of time... TIMING them. It's simple. Photocells drift. That's why you have to let the platter run for two minutes before you try to adjust it. Then, after a while you'll have to do it all over again

If you have the ones with the photo transistor (or whatever it is) you won't have to do nearly as much tweeking to keep them going. All you have to do is give them a "once-over" every few weeks. Unless you find something way out of whack you probably won't have to touch them.

If you have the PhotoCELL platters you can buy a kit to convert to photoTRANSISTOR. I'd say it's worth the money. Also, if you don't have one of these...

... you ought to get one. It's a tachometer. Just run that little wheel at the bottom up against the edge of the platter and read your RPMs off the needle. (Multiplied by two) The thing's worth it's weight in gold. I think it costs about $200 but if you have more than a few platters to take care of you will be glad you spent it!

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Joe Grace
Film Handler

Posts: 44
From: Maine
Registered: Feb 2000

posted 12-27-2000 03:01 PM

I re-timed the decks, and I ran the platter at full speed for a couple of minutes before I started the movie. It seemed to have worked. The problem seems to be that the motor was just a little too cold when I turned everything on in the morning. I adjusted the heat a little in the projection room, and the problem hasnt happened sense. The temperature was 64F and I put it to 68, it wouldnt go any farther than that, I am going to have to get someone to look at the pannel. Thanks for the feed-back.

Joe

For future refrence where is that Diode located that Paul was talking about?

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-27-2000 07:06 PM

Sorry that should have said 1 ohm not 100 the 100 is placed in the starter winding on several 3phase machines Almost every simplex installed in Canada has had for years the 1 ohm resistor added to allow for take up if the show was run onto a 6000' reel instead of the platter.
With a selsyen 3d installation the norm is 3ohm

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Paul G. Thompson
The Weenie Man

Posts: 4718
From: Mount Vernon WA USA
Registered: Nov 2000

posted 12-27-2000 07:15 PM

Joe, I'll check the schematic to see where that zener is. When I find it, I'll pass it along to you. Have a good one..

Gordon, do they use many 3 phase motors in Canada? I can imagine a power outage that could happen where the linemen got the phase rotation incorrect when power was restored. Now, that'll drive an inexperienced projectionist nuts! He/she'll probably walk out of the booth talking to themselves, maybe answering themselves, too!

Joe, I think the zener is located in the LED Power Control Module. The book does not identify it, and there is no schematic on that module.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 12-27-2000 07:26 PM

For many years Prevost and Cinemecanica were the industry standard here (especialy the Vic8) and they were all 3 phase

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