Film-Tech Forum ARCHIVE: Problem with modifying a Cat 280 into a cat 280T

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Posted by Martin Heilmann (Member # 2607) on 11-25-2005, 09:01 AM:

Hello there!

I am Martin from germany and I have a little problem:
I bought two Cat 280 SR cards and would like to modify them that they fit the CP200 instead of Cat 22to play back SR on format number 04.

On the first card I cut the jumper A (J801) but the other card does not have the jumper and this card has little differences in layout.
Here a more details of this card:
on front and top: dolby sr dolby spectral recording Cat no. 280 module
on top: Dolby Laboratories Inc 1986 Made in USA
on bottom: Cat No 280A ser no 3 310 assy 3370
behind the back cover: FAB A1PD3371 F 16-86

It would be very kind of you if you would tell me if I can modify this card to play back cinama-SR.

Yours sincerely

Martin

Posted by Alan Lyman (Member # 557) on 12-07-2005, 09:28 AM:

The only difference on a CAT280/280T,is that you can record with a 280.On the 280T,the jumber locks the card into playback only.This means that you should´be able to use the 280 in your cp200 as playback without any problems.

Posted by Sam D. Chavez (Member # 1841) on 12-07-2005, 10:19 AM:

The answer is incorrect. The jumper must be cut to disable the encode function if it to be used in a Dolby cinema processor. The "encode" pin on the backplane of Dolby cinema processors will put the Cat. 280's into encode mode.

This was not known by Ray Dolby when the design of the 280 was laid out. The card was way too complex to change when this problem was discovered, hence the need to cut the link.

Posted by Mark Gulbrandsen (Member # 72) on 12-07-2005, 05:44 PM:

But Sam, this still doesn't really address his issue. I also have two of these cards on my shelf. Apparently there are some earlier cards that do not have this link to cut, so what does one do with these cards...... that area of the card being entirely different from the later 280T's. Aside from insulating that pin of the card is there some component that can be taken out or one end of something disconnected? Geez, there's only just a few components on that card [Eek!]

Mark

Posted by Sam D. Chavez (Member # 1841) on 12-07-2005, 09:30 PM:

I never said I remember everything. Norm at Dolby should know the answer. If not, there is always Lonny.

Posted by Martin Heilmann (Member # 2607) on 12-10-2005, 07:18 AM:

The card without the jumper does nothing with the sound; the sound passes the card without any difference.

I was able to check this, because the CP200 I bought has no more SRA5, but the diodes set on the format link card. So if you play back sound on format 05, there is only matrix decoding but no noise reduction.

If you insert the card without the jumper and play back this channel only and you change between format 04 and 05 there is no difference in sound, not even encoding.

If you insert the card with the cut jumper, you can hear the difference in sound, because of working noise reduction.

If you are switching the formats 04 to 05 without playing a film, you can hear the same "psshhhhhhh" at both formats with the inserted card with no jumper on output level 10.

If you insert the card with the cut jumper, you can hear the same "psshhhhhhh" on format 05 (no noise reduction) and almost no "psshhh" if you switch to format 04.

Hope that my english is good enough that you understand my problems.

Yours sincerely

Martin