Film-Tech Forum ARCHIVE: cp 65 audio pops and loss

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Posted by Bernie Anderson Jr (Member # 410) on 06-28-2011, 01:52 PM:

Hi everyone...

It seems every time I fix one problem another problems comes up...

This year I replaced everything in my amp rack at home thanks to the carnage that D Cinema left behind.

This problem has been happening over the last couple of runs.

I get this "pop" in the audio, Its a lower pop instead of a snap and sounds mostly from center channel. Its random and its just a pop, not static.

The audio system is this:

-Dolby CP 65 with Cat 300 cards installed

-Component Engineering Reverse Scan

-DTS 6 wired to format 10

-SDDS 2000. I wired this as a pass through from the CP65 to the amps. Its in between the 65 and the amp and I'm using the XLR inputs/outputs.

The pop is in all formats except for digital and again present mostly in center channel. The pop is random and seems to have no relationship to the track but I've only heard it with signal present (film running). Almost sounds like a discharge of something.

The A chain is spot on and the processor is decoding with out any problem (clear L,C,R and Surround). There is slight back ground hiss in blank sequences almost like the noise reduction isn't working well (or at least Im so used to DCimena that I hear everything on analog)

The today, it popped and the audio went out totally. I raced into the booth to see where the problem was. I noticed that the Lights were lit on the preamp board and signal was present. So its not the reader, before i could look further, the audio came back on on its own. It does it even if the SDDS is on, off or in bypass, so its nothing to do with that. But when SDDS is on, I don't have the problem. I haven't tried it in DTS format 10 yet to see if its present there. But the pop is definitely coming from the CP65.

Any thoughts? Also, how hot should the boards get? It seems hot enough that I want to lay a fan on top of the processor blowing in. Even the EQ boards feel hot. I don't remember if this is how it was when it was in the theatre.

Thanks again for all your help.

Bernie

Posted by Tony Bandiera Jr (Member # 2365) on 06-28-2011, 02:13 PM:

Bernie, do a hard wire bypass of the SDDS. (Take it completely out of the system for this test.) And see what happens.

Why? Because of this:

quote: Bernie Anderson Jr
It does it even if the SDDS is on, off or in bypass, so its nothing to do with that. But when SDDS is on, I don't have the problem.

That is my first suspicion based on what you wrote.

When the CP-65 fails, look at the LED's on the CAT 249 module, all three should be lit at the same brightness.

The next prime suspect is the CAT150 card.

Finally, yes a fully loaded CP-65 will get very warm. It is important to leave at least one rack space above and below the processor, and use vented panels in those spaces.

Posted by Bernie Anderson Jr (Member # 410) on 06-29-2011, 12:23 AM:

Hi Tony,

Oh, I meant by the SDDS being on, that it was in SDDS playback with no problem. I will by pass it and go from there.

Does it make sense to by little fans to blow through the CP 65 for cooling?

Thanks

Bernie

Posted by Bernie Anderson Jr (Member # 410) on 06-29-2011, 09:24 AM:

Okay, so first rule should always be, check connections first. When I said that I saw the lights on the preamp board lit when the sound went out, it must have been at the exact same time that the sound came back on. I ran a reel today, bypassing the SDDS unit and the sound went out, totally. Great! Now I can see what the deal was. This time the green lights showing signal on the preamp board were out. I swapped inputs on the projectors and switch to input #2. Nothing. Pulled the board and reseated it. Nothing. I touched the cell wires and it came on. I looked closer all the wires were in the holes, but when I pulled on them, the neutral wire for the power came out. So evidently, it was the cell all along. So tightened up all those connections and everything was fine for a whole reel. Is there a trick to keeping those connections tight in the component engineering reverse scan?

What's you opinion of fans on top of the CP65 to help cool it? I can't imagine all that heat is good for the components.

Thanks

Bernie

Posted by Gordon McLeod (Member # 33) on 06-29-2011, 09:32 AM:

The 150E had heat issues with the voltage regulators

Posted by Ken Lackner (Member # 1002) on 06-29-2011, 10:40 AM:

quote: Bernie Anderson Jr
Is there a trick to keeping those connections tight in the component engineering reverse scan?

All I can think of is to make sure to use an appropriately sized screwdriver that fits the terminal to tighten down those Phoenix connectors. I can't recall ever having one come loose. Glad you found and fixed the problem and that it was something simple!

Posted by Tony Bandiera Jr (Member # 2365) on 06-29-2011, 05:56 PM:

Bernie, fans are not my first choice. Like I mentioned in my first reply, make sure you have 1 rack space MINIMUM both above and below the CP-65. NEVER stack anything directly on top of it. That is the first and most important step. Unless you have amplifiers or other gear dumping heat inside the rack, this simple step will keep the processor cool enough.

Fans will draw in dust and dirt, which can make overheating worse if the cards and cage are not cleaned out frequently. That said, it probably wouldn't hurt to add a fan or two. BUT, do NOT use 120 volt fans. Use 12v dc fans and a small 12 power supply (DO NOT tap the CP-65's supply!) that is switched on and off with your rack.

The CP-65 I have in my screening system right now is the one that came out of UC Irvine, where it was left powered up 24/7 since 1997. It did run warm there too as it was in a tight space. But that was in an air-conditioned booth.

On really hot days, I will open the front door on the CP-65 to help keep it cooler. I do not have air conditioning for my apartment.

Posted by Ken Lackner (Member # 1002) on 06-30-2011, 01:49 AM:

quote: Tony Bandiera Jr
my apartment.

And you have a screening setup? Nice.

At first, my reaction was "How can you not have air conditioning??" but then I remembered what my apartment hunt was like when I moved to L.A. [Smile]

Posted by Paul Mayer (Member # 355) on 06-30-2011, 11:33 AM:

None of the places I had when I lived in SoCal (Hawthorne and Long Beach) had air either. But both were within a few miles of the beach, so except for a couple of days during the summer, it didn't get really hot, not like Civic Center or The Valley where tempertures could easily top 100 degF. Some box and/or ceiling fans were all I needed.

Back to the CP-65...

Posted by Scott Norwood (Member # 30) on 06-30-2011, 11:55 AM:

For whatever it's worth, the cat. 222 "SR"/A card (which the original poster doesn't have) gets very hot. My CP65 originally had one of these installed. I replaced that card with a cat. 22 and two cat. 350s and it now sounds better and runs significantly cooler.