Film-Tech Forum ARCHIVE: Dolby Cat. 243 & General Question

This is topic Dolby Cat. 243 & General Question in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Ed Inman (Member # 2583) on 10-25-2013, 05:34 PM:

Just got my Dolby CP55 and it sounds very good, but some of the settings have been altered from the original factory specs. On Cat 243, the control logic card, I observed that someone changed the jumper block "wake up" wire from pin 4 (Dolby Surround) to pin 60 (non-sync). So when powered up, the processor defaults to "non-sync." OK--this is not a major problem, because when I then press the Dolby w/Surround format, the optical track plays normally. BUT, the "non-sync" LED remains on and the Dolby w/Surround LED remains off. But here's the real weird thing--if I try to change the format to "mono" the LED changes to "magnetic" and I get no sound at all from the optical track. I would note also that somewhere along the way the processor was wired to play DTS discs in the AUX format. Anyway, I wondering, would changing the wake up jumper wire back to "Dolby w/Surround" allow me to also switch manually to optical mono with no problem? Or is there something else I can do to make the mono format button work properly with an optical track? Many thanks in advance for any suggestions.

Posted by Stephen Furley (Member # 1277) on 10-27-2013, 04:51 AM:

It sounds like someone has added/moved/removed some of the diodes on the card to change the functions of some of the buttons. I've just looked at the CP-55 manual, but unfortunately it doesn't have a drawing of the card, which some of the older models did.

Can you borrow a card from somewhere to compare the diode positions? I think there was a card of this type on EBAY recently; I don't know if it's still there.

Posted by Sam D. Chavez (Member # 1841) on 10-27-2013, 08:21 AM:

This card was probably modified for an SRA5 or other external device.

The DA20 manual may have the drawings of the 243.

All else fails I have quite a stock of 243's.

Posted by Ed Inman (Member # 2583) on 10-27-2013, 08:28 AM:

Thanks for replying. I think you are correct. Looking at the board a little closer it appears someone modified it pretty closely to the diagram "Model SRA5 Installed Using Non-Sync Inputs" as shown in Section 3.2 here: http://www.film-tech.com/warehouse/manuals/DOLBYCAT222.pdf Still not sure why this would disable Mono but I might be well enough just leaving it alone so long as the basic Dolby w/Surround is working. If the EQ on an older mono print sounds too off I suppose I could just switch it to "bypass."