This is topic Changeover keeps changn' over:confused: in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.
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Posted by Matt Basford (Member # 652) on 02-21-2001, 05:22 PM:
Maybe a dumb question but a Strong changeover with Xetron auto. Would a short to ground cause it to close during feature leaving sound and light formats normal?
Posted by John Walsh (Member # 168) on 02-21-2001, 06:33 PM:
We need more info.. what kind of Xetron automation? The older ones are cam timer/relay based; the newer ones use TTL logic and/or a microprocessor.When is the c/o closing; at random times? when you do something else? Do you use the older foil-tape cues, or something newer?
Many Xetron automation functions do operate by grounding. For example, the START, STOP buttons both operate by grounding. When you press START, the first thing many automations do is close the c/o (in case it was left open previously.)
Posted by Matt Basford (Member # 652) on 02-21-2001, 06:52 PM:
They are Maxi 12's and it seems to occur about 1/4 to 1/2 through feature with nobody around. They are using the infared with the cue blocks.
Sorry for the broad question 
Posted by Aaron Sisemore (Member # 145) on 02-21-2001, 11:11 PM:
Is it happening randomly? With different prints?If not, you could have just the slightest piece of metallic cue tape remaining where it shouldn't be. Some proximity detectors can pick that up.
Aaron
Posted by John Eickhof (Member # 323) on 02-21-2001, 11:36 PM:
Two things...do you leave any overhead work lighting on (mainly small spot flood or simular) Even though Xetron claims these are not light sensitive, I have seen them cue from light bouncing off the film at the right angle. Also, when this occurs, is something else in the building starting up? Blower, AC or some large current draw? You may be experiencing a voltage spike into the power supply for the failsafe causing it to cue off...last, check the wiring and small plug that attaches to the failsafe, clen it with alcohol or contact cleaner then re-plug it in. Good luck------------------
John Eickhof President, Chief Slave
Northwest Theatre Equipment Co., Inc.
P.O.Box 258
Wendell, ID. 83355-0258
208-536-5489
email: jeickhof@nteequip.com
Posted by Paul G. Thompson (Member # 655) on 02-22-2001, 12:29 AM:
What kind of a fail-safe unit do you have? Does the projector motor continue to run?
Posted by Michael Cunningham (Member # 210) on 02-22-2001, 05:15 AM:
If you use the foil cueing strips, with a magnetic proximity detector type cue detector, as mentioned above I would definetly look for a small piece of cueing foil somewhere on the film. These can result when punching through the foil strips with a splicer. The little sprocket perf punch-outs are enough to set the detector off and they can tumble a good ways along the film before finding a new home to stick to. That's why, when I punch these cues, I always flip the film over and make sure that the perfs have been cut clean leaving no little squares. If a flap is still there, it should be cut away with scissors and carefully trashed. By carefully I mean don't drop this on your desk or floor or it will come back to haunt you...heh.-Mike
Posted by Matt Basford (Member # 652) on 02-22-2001, 08:18 AM:
It is not on every machine just one. It's a Xetron failsafe and yes the motor keeps running. Everything is normal(sound,xenon,house lights..) except the closed changeover. Where it seems to be happening there is no splice or anywhere near where a cue would ever be placed. I will inspect print once more just to be sure and maybe check sensitivity of the cue detector. Thanks for the help guys 
Posted by John Walsh (Member # 168) on 02-22-2001, 08:29 AM:
I think John E. is correct; We also had Xetron infared cue detectors. (A small rectangular reflective sticker(s) is placed on the emulsion side.)It also had an infared film failsafe (to detect if the film broke.) There's a small, 1" square pc board positioned right above the roller where the film goes through the cue detctor/failsafe. After about 2-3 years of use, ours began to 'trip' at random times. We complained to Xetron, and after not being able to do much, they replaced the infared film failsafe with a regular microswitch assembly.
Unlike the cue detector, there was no adjustment to set the 'trip' level.
Try taping a peice of scrap film in the failsafe, start the automation, then remove the film and see it it acts the same as it does during a show. The reason I suggest this is what doesn't quite fit is what happens after. If light is tripping the failsafe, it should act the same as if the film broke, which should put the sound back to music and bring up the house lights (yet you say the sound and light formats are normal?)
Posted by Gordon McLeod (Member # 33) on 02-22-2001, 08:34 AM:
I think you have a bad relay or logic board in the automation
If a false cue was causing it the hl would come up and music would come on
Also check the manual switch for the changeove I have seen them be flakey
Posted by Jerry Chase (Member # 660) on 02-22-2001, 09:02 AM:
I agree with the idea of faulty circuitry or a transient flipping the circuit. Not automation, but I remember the old Ballentyne sound change-overs that used an encapsulated solar cell and LED to give an isolated trip. Whenever there was a transient or momentary power drop-out from a twig falling on a power line, the sound would trip. One of our changeovers was so bad that at one point, even the striking of an arc would flip the sound to the dead projector.Then again, intermittant problems like this are one reason I never had a desire to repair equipment for a living. Good luck.
Posted by Darryl Spicer (Member # 711) on 02-22-2001, 09:22 AM:
Make sure the film edge is not making contact with the circuit board on the failsafe. I don't know if it's set up the same way as the fm35 by kelmar or not but the kelmars were having trouble with the circuit boards grooving out do to misaligned film paths. Causing the cue detectors to not function correctly
Posted by Steve Guttag (Member # 268) on 02-22-2001, 09:05 PM:
Just out of curiosity, what is your single cue (just one piece of tape)...is that the function that happens randomly? If so, I say it is getting a spurious cue. Depending on how the sensor is adjusting on the optical pickup, the film itself can case a false cue.Steve
------------------
"Old projectionists never die, they just changeover!"
Posted by Paul G. Thompson (Member # 655) on 02-22-2001, 09:53 PM:
I have to agree with Gordon on this one, except for the manual C/O switch. But, anything is possible. To isolate the faulty component, are you configured so that you can easily swap the fail-safe/cue detector unit with one that works properly on another machine? If so, does the trouble follow it?
That is the first thing I would try.
When you are fooling with electronic circuits, you can very easily chase your tail, especially when it comes to intermitting problems.
I learned many years ago to never make a flat statement in electronics.
Posted by Matt Basford (Member # 652) on 02-22-2001, 10:09 PM:
Thanks for the tips guys