Film-Tech Forum ARCHIVE: Wierd CP-500 problem

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Posted by Mark Gulbrandsen (Member # 72) on 08-10-2007, 07:46 PM:

I have a theater who's CP-500 gives the error reading below...

J-14/CAT675A ERROR... The unit stays in bypass as it should. Have swapped the 675's in both slots although I believe J-14 is the matrix decoder. I also tried the main computer and several other cards at Dolby's advice but to no avail. Have not tried the power supply yet but intend to in the morning when film is idle. However all three power indicator LED's on the main board are lit signifying the power supply is at least functioning. BAsically the problem lies in the analog system not in the SRD system... the SRD system is functioning ok onh its own as I get error rates and corners found LEDs.

Anyone else ever have this problem?

Mark

Posted by Louis Bornwasser (Member # 3063) on 08-10-2007, 08:03 PM:

There are several failure modes on the 500 that misdirect you to the wrong board. (In one case the software is WRONG.)

Swap one board at a time until you find it by elimination.. DO NOT rely on the screen. When I have this problem, I unplug the Digital cards until the SR portion works perfect.

Good luck! I feel your pain! Louis

Posted by Kenneth Wuepper (Member # 1174) on 08-10-2007, 08:36 PM:

The usual "black box" technique is to start replacing boards from the output end of the system and work toward the input or front end.

There is a remote possibility that more than one board may be the culprit so you need to leave the known good boards in the unit until the defective one or more are switched out.

After finding the bad board, restore the original working boards one by one starting at the input or front end. Leave all but the defective original boards in the system.

This technique is commonly used in servicing complex digital musical instruments. The service tech there must carry a spare set of boards since there are not duplicate systems nearby.

KEN

Posted by Mark Gulbrandsen (Member # 72) on 08-10-2007, 08:58 PM:

Thanks Ken and Louis!

It is definately an analog chain problem. As I mentioned the SRD sub system is functioning 100%. I'll pull the SRD subsystem completely out and then go through a complete swap out of the analog stuff tommrrow to see if I can pinpoint it but I already have swapped out most of analog system cards... excepting optical preamp and noise reduction. Power supply also to be swapped if all else fails... Luckily there are an abundance of CP-500's at this location.

Mark

Posted by Matt Zeiner (Member # 1914) on 08-11-2007, 08:08 AM:

my $.02: sounds like there may be 2 or more failures here... perhaps 675 at j-14 is bad and main board outputting bad clock, for ex. The SR-D stuff may function on its own in this case, but be unable to interface with the D/A's b/c of clocking errors. Go in the opposite direction - put cards from 'bad' unit into a known good until you find the culprits. look over aquisition card for shorted resistors before you swap it into good machine, tho...222 could be just outputting DC into the A/D's. coupla shots in the dark.

Posted by Mark Gulbrandsen (Member # 72) on 08-11-2007, 10:46 AM:

As it turns out both CAT 765A's had failed in the analog chain.

Mark

Posted by Kenneth Wuepper (Member # 1174) on 08-11-2007, 02:39 PM:

Matt,

Your reasoning is faulty if you are putting unknown boards into a working machine. The possibility exists for both units to become inoperative. Not all problems result in visible damage so you could endanger the second unit by inerting a shorted board.

Mark,

Good work! Happy that you found the problems. It is very unusual to find two boards with problems severe enough to shut down a processor. Only by leaving each of the known good boards in the unit can you find that multiple case of trouble.

KEN

Posted by Mark Gulbrandsen (Member # 72) on 08-11-2007, 06:17 PM:

Yea... I rarely have any 500 failures and there are alot of them in the areas that I service. Its been almost two years since I've had one fail. They just keep on ticking....

Mark

Posted by Steve Guttag (Member # 268) on 08-12-2007, 06:39 AM:

As an aside...ALWAYS watch out for J14 errors. When the CP500 checks itself...J14 is early in the checking process and if any other board has had an issue, it will cause J14 to not load in time and it will flag the Cat 675A in J14 as the culprit incorrectly.

Furthermore, the time that the Cat 675 in J14 has to load its program before it is called for failure is very short. As such, almost all failures in the digital chain show themselves as J14 failures.

I've had multiple card failures too, like in Mark's case but I've also had other cards cause a incorrect J14 failure and that is when I was told of the design issues in the CP500 that would cause an incorrect failure report. Apparently, it was always on shaky ground from a design standpoint...particularly as compared to say the CP650 where we have had almost zero failures except for power supplies and communications with the remotes.