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Date Posted: 21:44:10 01/25/02 Fri
Author: Potter
Subject: Re: Potter's 5508w schematic
In reply to: sphinx 's message, "Re: Potter's 5508w schematic" on 20:54:25 01/25/02 Fri

Looks like there's a still few bugs there. That cap has 2.5V on one end and almost the same at the other so it really won't matter much - use the overlay again. I remember reversing that one when I found the input to the video amp was slightly more +ve than the typical average output of the 4066. I was chasing a little problem with the average black level which was eventually fixed by the 1k resistor bypassing the output 220uF capacitor. Every station has a different average black level and because of the high impedance input to the 5508's output buffer the difference was being stored on the output capacitor with no way to discharge itself from the largest difference encountered (really screwed up the picture on some channels). My excuse will probably not be as good for anything else you may find.
I know of one other glitch on some early schematics - the connection of Vref (centre of the divider for the edge detectors) to pin 1 of the LM733 is not shown on the schematic but is OK on the PCB.

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