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This topic comprises 2 pages: 1 2
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Author
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Topic: CP55 Static
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Monte L Fullmer
Film God
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Posts: 8367
From: Nampa, Idaho, USA
Registered: Nov 2004
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posted 02-05-2005 03:34 AM
quote: Cam Jones guess tomorrow we can try to switch the cards from another processor to see if one of them is the problem.
True, that'd be your first step - "condemning" each card to see if one could be doing this static. And, while you're pulling cards, take a pencil eraser and scrub the gold contacts on the card(s), for hidden corrosion can cause irratic contact between the cards and the sockets. This is a common thing with Dolby products, and even with Ultra-Stereo units with their cards as well.
Then, if the static is still present, check the 'momboard' for any defects as well, for 'momboards' will develop hairline cracks and will have to be replaced.
Also, this static could be caused by a power supply that is getting "tired" thus not getting enough "juice" to the system. Swap out power supplies in the process.
CP55 units are at least 12 yrs old, and those power supplies do get tired after awhile. Dolby still has those CP55 power supplies in stock.
-Monte
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Pete Naples
Phenomenal Film Handler
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Posts: 1565
From: Dunfermline, Scotland
Registered: Feb 2001
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posted 02-06-2005 07:03 AM
Michael, for some reason static seems to prefer a sharp pointed ground rather than a nice smooth sound drum! I've seen the static problem described above many times, especially when polyester film base first appeared, before we learned about it's sensitivity to booth humidity. What I do when hit with this issue is to paint the cell bracket and the cell block (taking it as close to the tip as I dare without getting it on the cell surface) with conductive paint, taking it right back to the screws holding the bracket onto the rep set, having cleaned them with emery paper or a fibre glass pencil first. You still get the static discharge, but with the paint in place it goes to ground via the paint and not through the processor circuitry. The 'frying eggs' noise is more pronounced in theatres using Jax Lights (stands to reason, the pre-amp boosts all signals from the cell, including the unwanted).
Have any of you guys ever examined the surface of a cell that's been hit with this type of static for an extended period under a microscope? It looks like the surface of the moon, covered in pits and craters where the sparks have landed. More than once I've replaced cells damaged in this way, whilst there was no measureable difference, there is a definite audible improvement.
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