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Author Topic: CP55 woes...no output! Jon Miller Jedi Master Film Handler Posts: 973 From: San Diego, CA, USA Registered: Sep 1999 posted 04-12-2003 02:50 PM                     The Dolby CP55 I just installed in my home rig will not produce a signal at the output. It's stone cold mute regardless of source--film, auxiliary, or non-sync--even in bypass mode! From what I can tell, signals make their way to the Cat. 242 (B-Chain) card just fine. All level indicators on the Cat. 240 (preamp), Cat. 222 (NR), and Cat. 242 cards flash as expected while running a film (except the L signal-presence indicator on the Cat. 242, which broke in transit). I can get a decent waveform on an oscilloscope connected to the test points of the Cat. 242; adjusting the fader and cycling the mute button both have an effect on the waveform. I've removed, inspected, and reseated all the cards, including the Cat. 249 (voltage regulator) and Cat. 250 (power supply) module. All three status indicators on the Cat. 249 light up, showing operation of the voltage regulator circuit. The amplifiers are all working OK, proven by injecting a signal at the processor end with a CD player with clip leads on the output. I could find no wiring problems at the output terminal strip. I'm stumped...I think I've explored all the possible angles, but there has to be something obscure causing the problem. Is there anything else to check that may cause a loss of output? I'd hate to be stuck with an expensive doorstop. TIA!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-12-2003 03:09 PM                     In transit did the bypass relays get removed from the backplane as they are the direct path for bypass and if that don't work then I think they are suspect  |  IP: Logged Mark Gulbrandsen Resident Trollmaster Posts: 16657 From: Music City Registered: Jun 99 posted 04-12-2003 03:20 PM                     If its not the relays do you get Dolby Tone level on the NR card, any front panel LED's, any audio path LED's? Anything? Be sure the main power supply box has not become unplugged from the backplane. Mark @ CLACO  |  IP: Logged Jon Miller Jedi Master Film Handler Posts: 973 From: San Diego, CA, USA Registered: Sep 1999 posted 04-12-2003 03:48 PM                     Gord--The bypass relays are in place and click when the bypass switch is actuated. Mark--Yes, all indicators light...the front-panel indicators as well as those I mentioned in the original post. The power supply is locked in place. Right now I have to rely on a loop made out of a trailer; getting proper test films will come later. As a follow-up, I connected an amplifier to the test points on the Cat. 242 card. Even though the processor has not been tweaked yet, I do get decent sound from the test points.  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 04-12-2003 07:36 PM                    First off are you using a local or remote fader. If you are using the fader on the processor panel make sure that it is in the local setting. You could have a deffective Cat 242 B-chain Facilities card, cat number 243 control logic card, or cat 247 front panel card. Also check and make shure that wiring harnes for the cat 247 front panel card is plugged in.  |  IP: Logged Paul G. Thompson The Weenie Man Posts: 4718 From: Mount Vernon WA USA Registered: Nov 2000 posted 04-12-2003 07:53 PM                     I concur with Darryl.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-12-2003 08:27 PM                     Even in bypass remote fader is not an issue  |  IP: Logged Darryl Spicer Film God Posts: 3250 From: Lexington, KY, USA Registered: Dec 2000 posted 04-13-2003 10:14 AM                    Actually if you are using a remote fader and in bypass the remote faders don't work it reverts back to the local. if you are not using a remote fader and you have the fader selected as remote you will not have sound in normal operation. When you flipped the unit to bypass did the bypass indicator flash on the front pannel? If not then there could be a bad fuse for the bypass. If the fuse is good a problem could be in that cat 247 front pannel card. Most likely if everything is working I would check into a problem in one of the three cards that I mentioned above. This information I posted was stated in the CP 55 manual that I have here at home. If you have a manual or if you don't there is probably one here on the site in the manuals section. Go to the trouble shooting section and you will find the information that I have posted for your suspected problem.  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-13-2003 10:29 AM                     Since there is no sound in bypass as well we can assume that the fader card is working The pot on the front panel is a dual pot one segment is the VCA control the other is the bypass audio Check with a scope for the presence of audio on the input to the pot  |  IP: Logged Jon Miller Jedi Master Film Handler Posts: 973 From: San Diego, CA, USA Registered: Sep 1999 posted 04-13-2003 06:02 PM                     Problem solved! Decided to take a closer look at the block diagrams and trace the signals at the backplane PC board. First I confirmed signal presence at the Cat 242's socket, then I removed the three bypass relays to verify signals at the relay sockets. All well and good. Verified the correct orientation of the relays and reinstalled them...Guess what? I've got output now! For some reason, the bypass relays were installed bass-ackwards! (That's the way I got the processor.) I thought I heard the relays click when I checked the bypass switch, but I must have been hearing things...the relays make a loud, authoritative click when they work. Time to recalibrate my ears! Anyway, I think the relays are shot, anyways, as I am getting a mix of normal and bypass audio. Removing the relays and jumpering the appropriate contacts on the relay sockets has restored order for now. Thank you, Gordon, Mark, Darryl and Paul for your assistance!  |  IP: Logged Gordon McLeod Film God Posts: 9532 From: Toronto Ontario Canada Registered: Jun 99 posted 04-13-2003 07:19 PM                     Those relays caused loads of grief in the past on all the cp200's 55's and 65's as they sometimes tended to get contact problems  |  IP: Logged Rick Long Jr Expert Film Handler Posts: 211 From: Toronto, Canada Registered: Jul 2000 posted 04-14-2003 08:53 PM                     Given the number of times I've ever seen a CP-55 run in bypass, I'd say in a private screening room setup, leave the relays out jump the connections. You won't need them. Just remember the rule regarding the order in which you power the system up. Power amps off first, on last.  |  IP: Logged

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