Film-Tech Forum ARCHIVE: Attention CP500 Pros: Help needed

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Posted by Cory Johnson (Member # 103) on 12-16-2000, 09:23 PM:

Refering to a previous post with the QSC amp clipping, it seems we have a bigger problem on hand. We no longer have a Left or Right channel when we play back digital on our CP500. Before it was just clipping the left amp when we would turn the volume past 6, but know, the left and right channels are completely silent (nothing is even going to the amp). We have 4 other CP500s and we were told and one of the cards is bad in the 500. We are suppose to take the cards out one at a time and put in the cards from a "good" 500 until we have a left and right channel. Can we do this? It seems to me that it wouldn't be good to be swapping parts like that. Does anyone know off hand which card it might be? I check the event log and the only entry besides Startup is an "Illegal Instruction" error every so ofter. Please help! Right now we are playing it back in SR and it works fine (turn it to as loud as we want and it doesnt clip or silence the channels). Originally it was just clipping the Left amp, but as I mentioned above, now the left and right channel will be there for a second and then they are gone and we are left with center and surrounds and sub.

Thanks for the help in advance.

Posted by Randy Stankey (Member # 64) on 12-16-2000, 11:31 PM:

Swapping cards is okay to do. It's a pretty common troubleshooting technique. Just don't get the cards mixed up! If you do you'll be worse off than you started. I usually put a piece of tape on each card with the number of the projector on it.

Make sure you have the processor off when you pull cards and insert them. Do you work on computers and junk? Just use the same common sense you would for computers. After all, the CP-500 is just a highly specialized computer! (It's a stretch but the analogy fits.)

You can proceed in a few different ways:

1) You can just start at the left of the unit and swap out one card at a time until you find the one with the problem. (ie: The problem moves to the other house.)

2) You can look in the manual for the processor and find the "signal path" diagrams. For each sound mode, the signals take a different path through the unit. (Preamp>>>Noise reduction>>>martix, etc.) You can make an educated guess as to which card might be giving you the problem and start there.
The manual also tells you how to tell if each card is doing what it's supposed to. (ie: If this LED lights up, this card is receiving a signal..) With this info you can sort of "home-in" on wherever the problem lies.
If you look on the inside of the front cover to the processor you'll see an "abreviated" version of this... A number inside a triangle is the analog sound path and a number inside a star is the digital sound path if I remember right. Just start at #1 and follow the numbers.

Posted by Scott Norwood (Member # 30) on 12-17-2000, 07:34 AM:

Disclaimer: I'm not a CP-500 expert and I don't have the manual right here to refer to as I write (type) this.

Before you start swapping cards randomly, get the manual and think about the problem for a few minutes. You say that everything works fine with SR. This rules out several potential problems: the amp, the speakers, the wiring between the processor/amps/speakers, the optical preamp cards, the matrix card, the output card, and the crossover card (if you're using it). Thus, there's no need to swap out any of these cards (all of which have [at least on the CP-50, -55, and -65] adjustments which are specific to the projector and auditorium).

This pretty much leaves the digital cards as the ones worthy of swapping. I'm not sure if these have projector- or auditorium-specific adjustments or not, but I kind of doubt it. Try swapping them one at a time and see if the problem moves to the other house and is fixed in the first one. When you find the bad card, have it repaired or replaced.

Follow Randy's advice about turning the processor off (or putting it in 'bypass') before swapping the cards, and try to handle the cards relatively carefully.

Posted by Randy Stankey (Member # 64) on 12-17-2000, 10:31 AM:

Agreed, Scott:

It's not wise to just start swapping cards randomly. The more thought you can put into it before you start the better. That's the reason I suggested getting the manual out. Its troubleshooting section covers a bunch of stuff like that. Use that to develop a plan of attack first.

Basically, the motto is, "Look before you leap."

Posted by Scott Norwood (Member # 30) on 12-17-2000, 10:55 AM:

OK, I looked at the manual. The problem is likely to be in one of the following cards: 670, 671, 673, 675A, 680. These are the digital cards on the right-hand side of the processor. It appears that these can be swapped among processors without individual adjustments (but don't quote me on that).

Good luck.

Posted by Gordon McLeod (Member # 33) on 12-17-2000, 12:21 PM:

First rule out there isn't a amp/speaker problem
Put the processor into bypass and listen on the booth monitor as a mono sum should be sent to the 3 screen speakers Listen on the monitor and see if there is a output of the processor (swicth monitor to processor) and then on amp output
If there is sound with no distortion then the problem has been isolated to inside the processor. If the problem persists then it is external to the processor

Posted by Steve Guttag (Member # 268) on 12-17-2000, 09:36 PM:

A couple of thoughts...

First, the "digital cards" have signal presence LEDs on them...in particular the one labled "EQ"....are the left and right channels there? If so, I would rule out the rest of the digital cards and look squarely at the main module. Believe it or not, this little bugger can cause all kinds of trouble.

The Output card takes it's instructions from the main module on what channels to turn on and how to mix them. I have had a main module mix all channels together and spit them out of all channels!!! It is very possible that it isn't telling the output card to turn on left and right while in format 10. That would be the first module I swapped out...BTW I would unplug the units before changing out modules since some are still live even in bypass .

The main module stores all the EQ and level settings so it will not be correct for the theatre you put it in but it will tell you if there is a problem....try running a digital loop.

Steve

------------------
"Old projectionists never die, they just changeover!"

Posted by Peter Martin (Member # 649) on 12-18-2000, 05:15 AM:

Gee, the photos look sweet.

How old are you Scott anyway. Does your mummy know you're out?

Posted by Brad Miller (Member # 2) on 12-18-2000, 05:24 AM:

Peter,

I am sorry to say that your behavior on these forums has been unacceptable over the last few days. I have received 3 complaints of the way you have treated other forum members in the last couple of days and with your posts this morning regarding the CP500 and most specifically the way you are speaking toward Mr. Norwood (who is highly respected by the way), I don't believe anyone here will miss you.

When you mature a little bit, please email me so we may discuss this. In the meantime, I have pulled your registration. Good day.

Posted by Scott Norwood (Member # 30) on 12-18-2000, 05:25 AM:

Peter--the picture is 5 years old! I'm 24 now, but I've had that picture on my web page since the fall of 1995 and haven't bothered to update it. I need to find and scan a newer/better one, I guess.

Posted by Scott Norwood (Member # 30) on 12-18-2000, 05:58 AM:

Brad--don't worry about it. Even my good friends tell me that I look really dorky in that picture. They're absolutely right. It was originally a high-school yearbook picture, but, at the time, it was one of the better shots of me. I generally look bad in photographs for some reason, and this one was less bad than most of the others I could find at the time.

I'll try to dig up and scan a newer one soon.