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Topic: Dolby CP-45 Power Supply

Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 05-12-2002 12:29 AM

I have a Dolby CP-45 that only works in Bypass mode and the fault is not in the external power transformers (I've changed them).

Do I need a new back panel board? Or is there something else to try first?

------------------

~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 05-12-2002 11:02 AM

Are the power supply status leds lighting up? (plus and minus 12, and plus and minus 6 volts if I recall).

If those are not coming on and you are sure the transformers are putting out a.c., might be an idea to start looking for a bridge problem.

There may be a fuse in this thing, but I can't recall ever seeing one.

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Gordon McLeod
Film God

Posts: 9532
From: Toronto Ontario Canada
Registered: Jun 99

posted 05-12-2002 12:58 PM

Also is the correct transformer being used the backup one for a CP500 looks the same but is a different voltage

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 05-12-2002 08:39 PM

Gord: I checked them by swapping them out with another processor and they worked on that one.

But speaking of similar looking power supply units...

Are the Normal/Backup units identical?

------------------

~Manny.

Now...where was I ?
Leonard Shelby, MEMENTO.

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Rick Long
Jedi Master Film Handler

Posts: 759
From: Toronto, Ontario, Canada
Registered: Nov 1999

posted 05-12-2002 10:51 PM

Both the normal and by-pass supplies on a CP-45 are 24 volts, ac.

The CP-500 uses 16-volt transformers.

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Stefan Scholz
Expert Film Handler

Posts: 223
From: Schoenberg, Germany
Registered: Sep 1999

posted 05-14-2002 02:57 PM

The power supplies are on the large processor board, switchmode type. I had some of theese fail at a customer's site. You had to replace the whole processor board, but it was a swapout replacement, and a standardized repair fee.

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Manny Knowles
"What are these things and WHY are they BLUE???"

Posts: 4247
From: Bloomington, IN, USA
Registered: Feb 2002

posted 06-04-2002 12:04 PM

I have double-checked the following:

I have 4 LED's indicating power on the Cat. 511.

There is indeed a fuse on the Cat. 511 and I've changed it - I've seen them work in Bypass mode with a screwy fuse.

The transformers actually have "CP-45" printed on them. I have switched the one from Bypass to the one for Normal and it still only works in Bypass.

Do I need to replace the Cat. 512 board (back panel) or the Cat. 511 (main board)? As a point of interest, the 512 doesn't appear on the Dolby price list.

If I recall correctly, I've swapped out the 511 with one that's known to be working, but I could double-check that next visit.

But that's why I'm looking at the Cat. 512...it's the only thing I haven't changed and it's also where the power supplies get attached.

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