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Date Posted: 19:40:40 01/28/02 Mon
Author: sphinx
Subject: Re: Potter's 5508w schematic
In reply to: Potter 's message, "Re: Potter's 5508w schematic" on 21:44:10 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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Replies:

  • Re: Potter's 5508w schematic -- sphinx, 19:54:38 01/28/02 Mon
  • Re: Potter's 5508w schematic -- Potter, 14:44:06 01/29/02 Tue
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