Film-Tech Forum ARCHIVE: Strange Problem With CP500

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Posted by Matt Hollis (Member # 2954) on 06-22-2005, 11:26 AM:

At my theatre we own two CP500s which are now acting strangely. They are playing non-sync out of every channel. Our non-sync music is simply a stereo with the speaker outputs going to the 500s. The problem does not stop there however. Also, movies will now not play in digital and will play in SR only. Please help! lol

Matt

Posted by Dominic Espinosa (Member # 2122) on 06-22-2005, 11:45 AM:

Is this new or just suddenly happened?
Sounds like switched inputs or a burned board?

Posted by Charles Phillips (Member # 2594) on 06-22-2005, 11:52 AM:

I'm no expert but...
On the troubleshooting chart for the Dolby CP500, page 10-14 it adresses this issue. It says that the probable cause might be that the non-sync source may be set too high or there is an unbalanced / balanced wiring problem. It suggests turning down the output or turning off the non-sync source during the show. If not I'd look into what Dominic said about a bad card.

Is this happening with one print or all prints?

Posted by Matt Hollis (Member # 2954) on 06-22-2005, 11:58 AM:

The problem just now came up...

It happens in two different theatres with two different CP500s...

Matt

Posted by Randy Stankey (Member # 64) on 06-22-2005, 12:24 PM:

Sounds like you are "slamming" the inputs of your CP-500s with the output of that stereo at speaker level.

Turn the volume control down on the stereo.

Hooking speaker level outputs to inputs that were meant to take line level is like trying to make it drink water from a fire hose.

You need a distribution amplifier.

You can either make one from components availiable at Radio Shack, et. al., or you can buy one, premade from your cinema equipment dealer.

Here are just two examples. There are many more to choose from. They just happen to be two websites I could find off the top of my head.

Ultra-Stereo Labs

Smart Devices

Posted by Charles Phillips (Member # 2594) on 06-22-2005, 12:29 PM:

Randy. Could he have fried one of his cards by inputing sound at speaker level?

Posted by Randy Stankey (Member # 64) on 06-23-2005, 12:04 AM:

I don't know for sure. It is a distinct possibility.

The fact that the thing even still works at all says that it's not a goner yet. That doesn't mean you can't smoke it by doing that. It just means the thing is incredibly tolerant.

No matter. There are three things to do:

1) Turn down the volume on that stereo right away. Somebody's probably been tinkering with it anyway.

2) Read the manual and find out what kind of signal it's supposed to take.

3) Seriously think about getting a distribution amp. They make life SO much simpler. Even if one costs $1,000 that's STILL a lot cheaper than the CP-500 you risk frying.

Posted by Dominic Espinosa (Member # 2122) on 06-23-2005, 03:06 AM:

Running an amplified signal into a line input will sound terrible when it's turned down low enough to not clip. Usually because the amp it's coming off of is noisy anyway.

Posted by Michael Schaffer (Member # 1204) on 06-23-2005, 03:58 AM:

quote: Randy Stankey
3) Seriously think about getting a distribution amp. They make life SO much simpler. Even if one costs $1,000 that's STILL a lot cheaper than the CP-500 you risk frying.

You can get one even for much less than that. The MDS basic unit is about $250, each of the preamp cards which play 2 channels in stereo or 4 in mono is about $75. Obviously the actual price you are going to pay depends on what discounts your dealer has and what he quotes you, so it may even be less. Then all you need is some wire (e.g. Belden 8723) and a few RCA plugs. Wiring and setup of the units is extremely easy and quick. You have to homerun the wire to each rack where you can either solder on the RCA plugs or land the wire on a small terminal strip, then take a standard RCA cable, cut it in two halves, then use each of the end for one rack to go from the terminal strip to the non-sync inputs.
As the man from Erie pointed out, this solution is much better and financially much less painful than blowing up your CP500s.

Posted by Randy Stankey (Member # 64) on 06-23-2005, 11:46 AM:

quote: Randy Stankey
Even if one costs $1,000...

Of course, they can be had for WAY less than that.

The statement was meant to dramatize the fact that the cost of repairing the CP-500 would be WAY more expensive, not to mention the potential for loss of business.

$1,000 would be a small price to pay to prevent such a catastrophe.

Posted by Monte L Fullmer (Member # 2797) on 06-26-2005, 07:56 PM:

If he wants to use his stereo and is good with a soldering iron, he could tap across the opposite ends of the volume control "pot" with a two wire cable attached at each end of the "pot's" terminals then to an RCA jack - one hot and one ground (being sure in attaching the wires the same to the jack) being these are the input leads to the "pot" from the pre-amp section of the stereo before it heads to the power amp circuit of the stereo. And do it twice for the L/R outputs.

Then, he wouldn't have to worry about overloading the NS input of the processor.

Also, wonder if he has his custom format to perform "matrix encoded non-sync" - with NS playing to all channels.

-Monte