Film-Tech Forum ARCHIVE: Question about Cat 517 in CP-50

This is topic Question about Cat 517 in CP-50 in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Rob J. Buskop (Member # 3338) on 08-17-2014, 07:48 AM:

Just recently I inserted a cat 517 into the cat 117 slot of a CP50. When adjusting the channels to proper levels I found the center channel to be lacking in gain. Max. at trimpot was still very soft and at least some 9dB down.
Is the 517 directly interchangeable with the Cat 117 in the CP-50?
If it is, it should have the built-in center channel line amp as the 117 has. (L&R line amps provided by the Cat 22's).
Can't find a schematic for the 517 anywhere, so would appreciate your comment on this!

Posted by Steve Guttag (Member # 268) on 08-17-2014, 09:01 AM:

There are a couple of mods required to put a CAT517 in...my mind is a bit blank on it at the moment but one is to bypass the coupling capacitors on the backplane of the CP50. (They are on the INSIDE of the CP50). You also want to bypass the line amplifiers that are in the CAT22s since the CAT517 has its own, quieter line amplifiers.

Again, its been awhile so I'm a bit hazy on the specifics. If you look in the DA10 or DA20 manual, you'll see the CAT 517 block diagram which will let you know the output pins. The CP50 manual will have the signal flow so you can figure out where you need to "splice" the CAT517 in.

Note, if you are also using the CAT560 to have stereo surrounds, watch out. You'll have an inverted phase on the Left surround, as I recall, because that signal will go through an inverting op amp and the Rs signal will not. Again, I'm a bit hazy on the specifics at this late in the game.

Posted by Rob J. Buskop (Member # 3338) on 08-17-2014, 10:32 AM:

Thanks Steve, that was very helpful.
Have not been able to find a schematic for the cat 517 yet, but would like to have one for eventual repairs. Anyone?

Posted by Steve Guttag (Member # 268) on 08-17-2014, 02:08 PM:

The CAT517 never had a published schematic (nor the CAT 560 or even the later CAT 150s). Dolby stopped publishing their schematics.

Posted by Rob J. Buskop (Member # 3338) on 08-20-2014, 09:11 AM:

Thanks Steve for your information. The card's review in the DA20 manual was very enlightening and it is very apparent that a Cat. 517 cannot be used as a direct replacement for a 117 in a CP50.
As to the schematics, yes I know that the later cards schematichs are not in the P.D., but some people (me included) do have some unpublished schematics obtained via inroads to Dolby.
Anyway, my question has been answered and thanks again for your
assistance!