Film-Tech Forum ARCHIVE: CP50 center channel dropping intermittently

This is topic CP50 center channel dropping intermittently in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Dominic Espinosa (Member # 2122) on 05-10-2012, 09:35 PM:

Subject says it.

I've got a CP55 with SR on a newer Kelmar redlight reader -- the problem existed with the old Jaxlight that WAS in here last week.
It is dropping center channel intermittently.
I have dialog on the Left/Right pretty clean but it comes through in crackles on the center.

Definitely coming from the processor like this.

Thoughts?

Posted by Richard May (Member # 2627) on 05-10-2012, 10:09 PM:

Had the same EXACT problem with a CP65 last month and posted it here. Same EXACT symptoms. I was told to check the bypass relays on the back. I took them off, reseated them, and the problem never came back.

Posted by Sam D. Chavez (Member # 1841) on 05-10-2012, 10:11 PM:

I assume you are talking about the film formats, 01, 04 05?

First, what happens in bypass? Do you have a crackling noise? If so, which channel(s)? If no go to next step.

Check the green lights on the 150 and then on the 242. If the center green light is on more or less in sync with Left and right channels, look next at the surround green LEDs. Is the surround LED on the 150 card on dialog, it's likely the 222 or 150 but could also be the center Cat. No. 64, or the output relays that was a topic recently.

So, now you have a homework assignment.

Posted by Dominic Espinosa (Member # 2122) on 05-10-2012, 10:16 PM:

Thanks, guys.
I'll check it out!

Posted by Kenneth Wuepper (Member # 1174) on 05-11-2012, 06:53 AM:

Sam,

You are a great teacher and your help is always cheerfully offered.

Thank you for all of your sharing here on the FORUM.

Posted by Sam D. Chavez (Member # 1841) on 05-11-2012, 12:23 PM:

Thank you Ken. You're not so bad yourself.

I don't know about the cheerful part, that tends to vary depending, but I do try.

I did this for Dolby Labs for 14 plus years and always enjoyed this part of the job. I also taught Dolby school for most of those years.

Now, if only I could keep all that info from draining out of my skull.

Posted by Dominic Espinosa (Member # 2122) on 05-11-2012, 06:58 PM:

Thanks for the guidance.
So, I got down here to look at it and it's actually a Cp50 and I don't see a cat 222 card...

Posted by Louis Bornwasser (Member # 3063) on 05-11-2012, 08:21 PM:

Well, no relays. Center channel only "exists" after the 150 card, check the 150, swap a 64 and the output line amp is on the 111/117 card.

Note: left and right output line amps are on the respective 22 cards. Louis

Posted by Steve Guttag (Member # 268) on 05-11-2012, 08:53 PM:

Don't forget...the CAT 112 (switch card) also has the audio pass through it and if the Non-Sync/Opt switch is getting noisy...so can ANY of the channels.

Posted by Sam D. Chavez (Member # 1841) on 05-11-2012, 09:24 PM:

I have to correct Louis' statement.

The Cat. No. 150 produces the center as well as the surround channel and if it is a version equipped with the green signal presence LEDs, you can "see' if it is decoding all 4 channels.

Dominic, you should not ask for help until you know what you are dealing with. It's waste of time for all involved.

Posted by Tony Bandiera Jr (Member # 2365) on 05-14-2012, 01:00 PM:

Sam I agree but your statement to Dominic was a bit harsh. [Big Grin]

(Since you and I are currently dealing with the same irritation I understand it though. )

Dominic, if you find you need a CAT 150 or 117 card let me know, I haven't tossed the ones I listed yet...I might even have a CAT 112

Posted by Sam D. Chavez (Member # 1841) on 05-14-2012, 03:01 PM:

Tony,

You are right, I do go thru bouts of cranky (bet you hadn't noticed) but you should get the model # close. 55 vs. 65 OK, easy mistake, but CP50 to anything else, no.

It's my own version of tough love.

Posted by Tony Bandiera Jr (Member # 2365) on 05-15-2012, 02:27 PM:

LOL yep, and you're right about how the model confusion in this case is a big deal.

Louis mentioned that the Left/Right line amps are in the cat 22 cards, is that correct? I didn't think so.

I'm going to see our "friends" on the 23rd. Wish me luck. [Smile]

Posted by Sam D. Chavez (Member # 1841) on 05-15-2012, 03:38 PM:

Louis is right about that part. It was some engineers idea of saving a buck and using a spare line amp on the Cat. No. 22's.

This later got fixed on 517 upgrade of the 111/117 cards.

Posted by Dominic Espinosa (Member # 2122) on 05-16-2012, 07:18 PM:

Thanks to you guys, so far.
Sam/Tony/Louis I always appreciate your advice. Even if it comes with a scolding for being an airhead [Wink]

I tried the format card and had to wait a few days to see if it recurred. The center just fades in and out, as if you were fondling the gain. There's no crackling or distortion though.

Posted by Tony Bandiera Jr (Member # 2365) on 05-16-2012, 07:27 PM:

With the sound fading in and out, I'd suspect either the CAT 150 (40%) or more likely the CAT 117 (60%+).

Keep us posted.

Posted by Sam D. Chavez (Member # 1841) on 05-16-2012, 08:10 PM:

The edge connector on the 112/113 slot can be mighty flaky after all these years. Try some electronic cleaner.

Could be the 111/117 as Tony says, or it could be one of the cat. No. 64's. Try swapping the center 64 with one of the others.

Does your Cat. No. 150 have the green signal presence lights on the front? If so, keep an eye on that when the center channel sound fades.

Do you know for sure it's not the center power amp failing?

Sorry for the scolding.