Film-Tech Forum ARCHIVE: Basement Reader Analog problem

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Posted by Demetris Thoupis (Member # 833) on 08-01-2004, 11:52 AM:

How about this problem,
I can not mention the brands of the projectors but we are talking about basement readers (reverse LEDS). The problem which is identical to all three screens is that when the film is in analog, the centre channel seems to be playing all in the surrounds and the surround in the centre channel. The input from the projector to the sound processors (all CP650 without EX) is coming in very low. I've tried the Jiffy test film and when the sound is supposed to be rotating clockwise from the left speaker to the surrounds, the rotation goes LEFT - SURROUNDS - RIGHT - CENTRE, meaning when the centre is supposed to be playing the surrounds are and vice versa. Could there be a problem with the wiring of the Basement reader? Any ideas?
Thanks in advance.
D

Posted by Stephen Furley (Member # 1277) on 08-01-2004, 12:08 PM:

Sounds like either the Lt or Rt, but not both, inputs to the processor from the projector(s) has been connected with its polarity reversed.

Posted by Mark Gulbrandsen (Member # 72) on 08-01-2004, 12:08 PM:

Check to be sure that the plus and minus connections for each channel are correct at both the scanner and the processor. This is what happens if they get reversed.

Mark @ CLACO

Posted by Manny Knowles (Member # 1171) on 08-01-2004, 12:45 PM:

In any event, I would recommend A-Chain alignments for all of those systems.

Posted by Sam D. Chavez (Member # 1841) on 08-01-2004, 02:11 PM:

Another great new picture, Manny.

Assuming the analog did not always behave this way and once was normal, I would look into whether you have burnt out segments in the 2 x 12 LED arrays. This was quite common on IR LEDs. It also occurs very infrequently on Red Leds as well. The light should appear to be one continuos slit of light if you put a piece of paper in front of the LED.

If it missing segments they are usually in the middle where the LED runs the hottest.

Missing Leds play hell with the matrix and the result can be what you are describing.

Posted by Mark Gulbrandsen (Member # 72) on 08-01-2004, 03:37 PM:

Donno, I have replaced close to 20 red leds in the last 60 days. Of course they were in excess of 5 years old and had not been switched off. All had multiple failed segments. Most were in CAT 701's, others in Kelmar scanners.

The good news is that I've saved them all and plan on making a RED LED hat to wear at next years Showest out of them.

Mark