Film-Tech Forum ARCHIVE: Very strange Dolby CP65 issue/problem

This is topic Very strange Dolby CP65 issue/problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Joe Redifer (Member # 3) on 06-21-2008, 07:54 PM:

We have a Dolby CP65 processor paired with a DA20 for our large giant screen auditorium which of course people from out of state travel to just to see a movie in. It has been having some weird issues and last night I noticed an issue which appears to be new.

Firstly, every once in a while (seems almost sporadic), the analog sound will be extremely low, crackly, distorted and unintelligible when in A-type or SR (we have a Cat222 SR/A card). When mono is pressed, all sounds fine. At first I thought maybe I either didn't close the pinch roller for the sound drum on the fantastic Simplex™ projector or maybe I threaded it incorrectly (yeah right... I'm me)! No on both accounts, all was fine. Run a loop of film and the same thing happens. Reset the lateral positioning and Dolby Tone and problem is still there. Go home and come back the next day, problem is gone. The CP65 and the amps never power off at night, by the way. One of the cards (forget which one... it is towards the left) has a plate on it that says HOT!. You probably know the card. Anyway there is a piece of masking tape on top of the HOT! label that says something like "distorted" in handwriting and it appears to have been there for awhile. Coincidence? Any suggestions?

The other issue which just popped up and baffles the hell outta me is that the optical sound plays even when Non-sync or Digital (format 10) is selected. It's not in bypass. I have tried rebooting the machine, the DA20, everything. The fuses on the front are all fine. The sound plays in SR stereo with surround as it should when that is selected, when you switch it to A-tye, it plays in A-type and you can hear the audible difference. Same when Mono is selected. When digital is selected it seems to be playing in SR as I cannot hear any difference at all when I switch back and forth between the formats (digital is definitely NOT playing). When Non-sync is selected, the optical sound increases in volume. MUTE still works, thankfully. Could this be in any way related to the previous problem? What could cause something like this?

I'm pretty sure the CP65 we have was purchased at a garage sale or maybe a thrift shop. It looks as if it were used as the ball in a soccer game. It has no door hinge and if you are not careful when touching the latches or even pressing a button, the front panel will fall off and hang by the ribbon cable (which seems to be firmly connected on both sides). Any ideas?

Posted by Louis Bornwasser (Member # 3063) on 06-21-2008, 09:05 PM:

Joe: I cannot help with the highly technical parts of your problem except to suggest substitution. The 150 card is the one that runs hot and is a good place to start due to its complexity.

The door hinge is readily available from any Dolby dealer; it will help psychologically. Louis

Posted by Joe Redifer (Member # 3) on 06-22-2008, 06:59 PM:

Could the Cat150 be in any way related to the format thing as well? [Confused]

Unfortunately we only have one CP65 so troubleshooting is very difficult since we don't have another unit to swap cards with to see what happens. We do have some CP50s and a CP200 lying around not being used, but those aren't compatible.

Posted by Louis Bornwasser (Member # 3063) on 06-22-2008, 09:01 PM:

Try swapping the 150; it's the only board that will swap. Louis

Posted by Joe Redifer (Member # 3) on 06-22-2008, 10:58 PM:

OK will do. Unfortunately it might be a few days before I make it back to the theater. I assume you mean a Cat150 from a CP50 and not the 200, right? Or is it in the 200 as well? I didn't see anything in the 200 that could be swapped.

Posted by Louis Bornwasser (Member # 3063) on 06-23-2008, 11:26 AM:

Any cat 150 card will swap with any other. All pre-cp-500 processors have one. Louis

Posted by Joe Redifer (Member # 3) on 06-25-2008, 09:30 PM:

The 150 card didn't help the format issue, but it may have solved our other "bad sound" issue. No problems with analog sound yet but it was very sporadic in the first place.

Does ANYONE know what could be the cause of the format issue I described in my previous posts? What card could be at fault? Or could it be the electronics on the front panel itself?

Posted by Sean McKinnon (Member # 612) on 06-26-2008, 10:35 AM:

Has the format issue always been there? I would suspect that someone at some point in time modified something on the backplane. I would check that out and if that doesn't do the trick I would try swapping doors. Maybe the buttons on the door are not making (or breaking) thier connections properly.

Posted by Pete Naples (Member # 761) on 06-26-2008, 11:25 AM:

The distorted crackling.... I've seen this being the fader VCA on the Cat242 B chain facilities card. Usually occurs when the the processor is well warmed up. Other than that I concur with the suggestion of the Cat150, doubt the 222SR/A is at fault as you say it happens in both A and SR, generally when those go bad it's A or SR but not both.

About the format thing, check that it's got a Cat443 logic card and not a Cat243 from a CP55, failing that look towards the diodes on the 443, maybe one or more is missing, misplaced or damaged.