Film-Tech Forum ARCHIVE: unexpectable cue sound

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Posted by Jae-Eun Jang (Member # 1412) on 12-28-2002, 12:39 PM:

hi! i'm a projectionist in seoul, working for CGV.
i would like to ask something i wonder theseday. it happens in the morning when i ignite the lamp manually to check the lamp(i use christie), it makes cue sound at the same time..i thought maybe the light from the console could reach to cue sensor..but, does not cue sensor read only cue tape is silver color..? does anybody know? help..

Posted by Ian Price (Member # 14) on 12-28-2002, 12:45 PM:

I wasn't aware that Cues made a sound. I think what you are hearing is a relay in the automation latching. When you strike the lamp, it must be linked to a series of automation commands and you hear relays closing.

Posted by Pat Moore (Member # 380) on 12-28-2002, 01:18 PM:

Yobosayo, Jang.

Do you mean that when you strike the lamp, a cue is detected by the automation or that a cue is generated by the cue detector?

Most cue detectors use a proximity detector that senses the presence of the metal foil tape on the film. It's possible that the detector's trigger circuit, or the automation itself, is sensitive to the electrical noise generated by the ignition of the xenon lamp.

Does this cause a problem during normal operation of the show? It may be as Ian said above, that you just hear relays clicking in normal operation, but if a cue is generated by the ignition pulse to the lamp then you have some other problems.

We look forward to getting more information and welcome!

Kamsa-Hamnida.

Pat Moore

Posted by Steve Guttag (Member # 268) on 12-29-2002, 10:26 AM:

Christie, for better or for worse, grounds the negative side of their DC power.

As such, when the igniter functions, you will be impressing a lot of noise onto the ground system. This can affect everything that is on the ground system. Not only can it false-cue but it can and often will put a "zap" in the sound at the point of ignition.

Your problems will be worse if you don't make "homerun" lines for your gound. That is, each circuit should have a separate ground wire going to the ground buss in your electric panel. Ideally, you would want computer based automations to be on a different, isolated ground from such noisy things as igniters, motors or dimmers. The same holds true for the sound system a good clean ground is essential.

Steve