Film-Tech Forum ARCHIVE: Dolby CP65 issue

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Posted by Richard May (Member # 2627) on 04-05-2012, 10:00 PM:

This is a weird one. Center channel keeps fading out completly for a while then comes back. The LED on the 242 card never dims. Sometimes the sounds gets staticy as is fades. I thought it was the amp but I changed channels and then changed amps and it still does it. I pulled all the cards and reset them. Sounds like it's in the 242 card somewhere. It does it in non sync, digital and mag. All other channels are fine.

Posted by Sam D. Chavez (Member # 1841) on 04-05-2012, 10:30 PM:

It's likely the 242 as stated, but it could also be the bypass relays. There are 3 of them behind a metal cover on the backplane.

Try switching them around. Also check the screws holding down the audio out terminal strips. They are loose a surprising amount of the time.

Posted by Richard May (Member # 2627) on 04-06-2012, 11:51 AM:

Thanks Sam. Can I assume that the middle relay is center channel? I swapped it with the left.

Posted by Tony Bandiera Jr (Member # 2365) on 04-06-2012, 02:43 PM:

Richard:

Nope. The relays each handle two channels and if I recall correctly it is in order from left relay to right relay as L, C, ; R, SUB, ; LS, RS.

Are those relays white or black? I recall that there was a problem with one of those two styles, I think it was the white ones.

In any event, they can be readily sourced from Mouser or Digi-Key for replacement.

Posted by Richard May (Member # 2627) on 04-06-2012, 03:38 PM:

Thanks Tony. I'll swap them again. I have a feeling it's not the relays though. It was only center dropping out. I would think 2 channels would drop out but I'll try swapping them anyway.

Posted by Louis Bornwasser (Member # 3063) on 04-06-2012, 04:09 PM:

If you "whack" the relay, sound will likely come back. I have had a surprising number of relay problems in the last 24 months; no problems before on Dolby. Louis

Posted by Tony Bandiera Jr (Member # 2365) on 04-08-2012, 11:21 PM:

Richard:

You're welcome. But yes,it is possible for only one set of the contacts to act up, so don't rule it out quite yet. And try Louis' smacking the relay suggestion, that will pinpoint which one is the troublemaker.

Louis: Yeah it seems that relay problems crop up in cycles. I have pulled the speed control card from one of my Kinotons (the one that was the subject of a thread a while back) which has a bunch of bad relays on it..at a replacement cost of over $10 EACH!! For now I have the card jumpered out to run at 24 frames. Oddly it is only the one projector acting up. (So far.)

Posted by Richard May (Member # 2627) on 04-09-2012, 06:24 PM:

I'll keep an eye on it. I swapped the middle and the right before I knew which ones were which. I did reseat the left one though. Hasn't happenned since.