Film-Tech Forum ARCHIVE: QST: DOLBY CP 500 OPTICAL INPUT

This is topic QST: DOLBY CP 500 OPTICAL INPUT in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Martin Daian (Member # 1779) on 12-09-2010, 08:43 PM:

Hello Everybody, i am installing a CP 500 processor, the analog sound reader on the projector is a standard stereo solar cell, my problem is that when i connect the wires to the optical input on the CP 500 in Proj 1 or in Proj 2 i have not sound but if i disconnect the wires and touch with the hand have signal in both chanels of the two optical inputs, anybody know where will be the problem, is possible that the cp 500 need to have connected the ByPass Power Supply to activate the optical input correctlly?, any help appreciatte,

Thanks,
Martin

Posted by Marin Zorica (Member # 1716) on 12-10-2010, 04:26 AM:

Bypass in only used to get aux supply for preamp so you got sound, but in normal operation you don't need it.

If there is sound when you touch connector, that means input is working......you probably did check wiring to connector and cell?

It can be that cell is bad, not common but it can be....if input is working that means only problem is in cell or wiring, but if you have, try to plug in other preamp, just to be sure is that.

Posted by Martin Daian (Member # 1779) on 12-10-2010, 11:17 AM:

Hello Marin, Thank you for Reply to me, the cell is good that after no sound on cp 500 i install a CP 55 and works perfect, is rare, also the wires of the cell are okey, is like a impedance adaptation problem between the cell and the preamp input of the cp 500, when touch with the hand have hum noise signal in both channels so the input on cp 500 works, the problem is when i connect the cell to the processor no sound and touch with the hand in parallel the input and not more hum noise signal, i not remember okey but i think that some years ago i see a cp 500 processor that in the preamp input connector on the rear panel have some resistors or diodes connected in place with the cell wires, anybody will know about if when using solar cell need any modification on the CP 500 ? maybe with reverse scan not have this problem that reverse scan have balanced outputs ?,

Thank you,
Martin

Posted by Marin Zorica (Member # 1716) on 12-10-2010, 02:53 PM:

I did worked both with rev scan on CP500 and normall stereo cell's....it can be maybe one input line (+ or -) is bad so that maybe did get problems, but in case of some resistors or so, only I tought signal with cell should be lower....nothing much. As i know for manual, there is nothing except projector 1 or 2 power on jumper.