CP650 Dolby Digital Not Working Anymore

[Kyle Mikolajczyk]

Thank you everyone for the help. We removed the Cat 773 card and sure enough that seems to have been the issue. The CP650 is no longer randomly freezing. This of course did not fix the Dolby Digital decoding issue, as we now don’t have that card in the 650! I am looking to purchase a working one, as this seems to have been the issue. Looking at the card does not reveal any obvious issues unfortunately. But, now that the issue has been found we can finally fix it.

Side note, anyone ever seen a Cat 773 card fail like this?

[Kieran Hall]

I'm still a little suspicious of the PSU; not exactly an apples-to-apples comparison, but we had our CP500 behave very similarly to this before the power supply gave up the ghost entirely. Seems reasonable that reducing the load on the 5V rail would temporarily make things a little happier.

[Sam Chavez]

CP650 power supply failure is the #1 failure mode. And all sorts of oddnesses happen when the supply is failing. We have new ones in stock as well as brand new 650's.

[Marco Giustini]

Kyle,
grab a multi meter and probe the various rails of your psu when the 773 is in.
an oscilloscope would be better but with a merger you may be able to see some drops/instability of the rails

[Kyle Mikolajczyk]

I checked all the power test points and the power was within the spec according to the manual, so we know the voltage is OK. But I do understand that capacitors could have other effects. Ill keep you updated.

[Sean McKinnon]

Out of morbid curiosity have you tried hooking up a scope to the video and clamp test points on the 650? Scope settings are in the manual. Do you see a video signal when the readers are attached?

[Randy Stankey]

If this was my system, I'd give it a full calibration from the ground up just like it was freshly installed.

Start with the LED. Make sure it's at the right voltage/current. Check to be sure all the elements are lit. Align it X/Y/Z & pitch/roll/yaw, for best brightness and even illumination.
Hook up an oscilloscope. If you have the software, also hook up DRAS. I like to use them both.
Align the reader using your scope and DRAS for confirmation. (The procedure is in the manual.)

While you are at it, double check your film path, above, below and through the reader are right. I have seen Dolby Digital systems that run at 7-F-7-F even though the reader seems to be in perfect alignment but, if you apply a tiny bit of back tension to the film above the reader, the system will run at 1-0-1-0.

My CP-650 with BACP Dolby reader at Mercyhurst had exactly that problem. I solved it by putting a Kelmar film cleaner (with Film-Guard) above the reader so that it gave some back tension to the film.

If I had a good print with a good Dolby track and I kept the film clean with Film-Guard, that reader would run at solid ZEROs for almost the entire movie!

[Marco Giustini]

I checked all the power test points and the power was within the spec according to the manual, so we know the voltage is OK. But I do understand that capacitors could have other effects. Ill keep you updated.

a faulty PSU can have unstable rails. I've had one which had a fault on the feedback circuit and the rails would start jumping after a while (the LCD backlight was visibly flickering) until the unit would freeze. This may or may not be your issue of course.

And indeed an oscilloscope may be a good starting point unfortunately. Set it up with the DA20 and then check what the 650 sees.

[Randy Stankey]

And indeed an oscilloscope may be a good starting point unfortunately.

Unfortunately? Knowing how to use an oscilloscope is part of the job!
A technician who can't use a scope is like a mechanic who doesn't know how to put air in the tires.

If you don't have one and can't borrow or rent one you should be able to get one, for cheaps, from Ebay.

Yes, the power supply might be part of the problem, especially on older units.
However, I still recommend doing a full-fledged tuneup. It's much easier to diagnose problems when you know that everything is aligned and calibrated the way it should be.

If you can't get something to calibrate, that would be a clue to point you in the right direction to finding the problem.

It will be much more difficult for you if you haven't verified that your LED is good, your lens and sensor are aligned, your cables are sound and connected properly and your film path isn't right.

[Marco Giustini]

Randy,

You're misunderstanding me. I'm assuming Kyle is not a technician so "unfortunately" he will need some tools in order to do the job. Scopes are cheap nowadays but if you're not a technician you may not want to buy one just to diagnose a sound processor.
Clearly if you are a technician, a scope is a solid part of your toolkit.

A full tune-up is never a bad thing. But since the same reader works with a DA20, I feel it's not on top of the recommended actions at the moment. If the DA20 can read it, the 650 should as well.

Kyle,
Before you dig into this too much, please do check you have selected the right projector as mentioned before. If the wrong projector is selected (or wrong motor start, Steve!), the symptom is "no dolby digital" as you describe.

[Randy Stankey]

You have a vintage projector? You're a technician, now! Here's your hat!

In the booth at Mercyhurst, I had my own scope and kept it in the booth on the bottom shelf of the sound rack where the processor was. I weaseled the wires up, through the rack and kept them plugged in almost all the time. I had an old computer on a side table next to the rack, loaded with DRAS and the CP-650 setup program.

I sometimes just turned the scope on during any, old movie and let it run. Turn the brightness down as low as you can. You don't need much in a dark booth. Plus, it saves your phosphors.

Mostly it was because I thought it looked cool but it's also good to be able to check on things at a glance. Besides, when it comes time to make your regular tuneups or if you ever do have a problem, the scope is right there, at the ready.

Same thing with DRAS. It's nice to let DRAS run for an entire movie so that you can see the histogram for the whole show.
It was nice to be able to say that my error number never went above 4 and to be able to prove it.

I also agree that the motor-start/projector-select relay connections should be checked. Cables and power supplies, too.
I assumed that, since other guys mentioned those things, above, that those issues were already brought to attention.

When I said to do a full calibration and tuneup like you're doing a fresh install, that means to start at page one of the manual and check everything. Cables and selects included.

Having a DA-20 available so that you can compare results or keep it as a backup is a good idea, too!
These days, and in the future, you might not have access to replacement parts like we did, before. Always smart to have backups for your backups!

The thing is that we're working in the unknown, here. In this problem (or any problem) we need to eliminate as many unknowns as possible.
Doing a full tuneup, from the ground up is a good way to eliminate unknowns.

I've got a little ulterior motive, here, too. If he's going to be in charge of caring for a projector system, performing tuneups is something that he'll need to do. No better time than the present to learn how...while he's got a whole team of guys standing over his (virtual) shoulder, ready to help.

That's why I gave him a hat!

Join the club! We'll teach you the secret handshake at the next meeting!

[Kyle Mikolajczyk]

I really appreciate all the advice and tips in this thread! Regardless of the outcome I do intend on performing the tune-ups (Although I will say the Kinoton readers that were installed on the DP70s are super reliable, been installed for 20 some odd years with no issues). Getting an oscilloscope when I am 10 feet from the Electrical Engineering building on campus will be a piece of cake. I did manage to get a DB25 cable and sure enough the DA-20 sounds great while we sort out this issue with the CP650.

[Kyle Mikolajczyk]

Side note, does anyone know where I could find the DRAS software?

[Randy Stankey]

Right here, at Film-Tech!

DRAS software:
http://www.film-tech.com/warehouse/w...592&category=2

DRAS manual:
http://www.film-tech.com/warehouse/manuals/DRAS.pdf

[Kyle Mikolajczyk]

Thanks for the links! The manual seems to reference a newer version however, as this one requires DOS (I have got it to work on DOS but I am afraid it might be too old for the CP650).