Film-Tech Forum ARCHIVE: BACP red reader problem

This is topic BACP red reader problem in forum Film Handlers' Forum at Film-Tech Forum ARCHIVE.

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Posted by Josh Jones (Member # 447) on 01-12-2008, 02:59 PM:

A theater I'm currently servicing is have problems with their BACP reader in a Simplex XL sound head with Super Simplex atop. Cell outputs are wired together and driving a Toa PA amplifier. The playback audio will pop, click, and sometimes exhibit static. I could duplicate the complaint by tapping on the led bracket. After this discovery, I cleaned the face of the LED and the bi-pin header that plugs into the bracket. The problem still persists, but is much less pronounced.

So I guess what I'm asking is, was there a bad run of these, or is this a common problem that anyone has heard of before. My next attack I suppose would be to hook a scope up to the LED line and see if the voltage jumps while the bracket is tapped, indicating an intermittent connection to the LED.

Josh

Posted by Gordon McLeod (Member # 33) on 01-13-2008, 12:57 AM:

You may want to put two summing resitors in the cell outputs

Posted by Sam D. Chavez (Member # 1841) on 01-13-2008, 12:58 PM:

If the noise or static happens more or less all the time (so one can catch it happening) I would block the light coming from the LED into the lens. If the noise is still there, you can pretty much rule out the LED without the use of a scope. The impedance of the LED is so low, the scope won't tell you much anyway.

Assuming no loose wiring or bad grounding, most problems within these readers have to do with the solar cell itself. or the mini backplane inside the reader.