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Date Posted: 19:50:54 12/18/01 Tue
Author: lcs
Subject: Re: Bad picture in Canton 4.2
In reply to: Potter 's message, "Re: Bad picture in Canton 4.2" on 06:20:45 12/18/01 Tue

>The interference sounds like an AGC problem IE
>horizontal bands associated with large brightness
>changes and especially if you are losing lock on
>extreme changes eg explosions.


May be. I use a 6dB attenuator in the cable because
the signal level of some channels is too high. This
helped but the interference in brightness is the same.

The board was first connected to the video output
of a tv monitor, feeding another monitor (hence no agc).
Later i opened up the video line of a VCR and implanted
the 3chip in the middle. Initially the signal level
coming from the tuner was low and some channels did not
lock. Then I built a new video amp and the picture got
better, but in both cases, there is always that same
interference, it doesn't matter if the signal is high
or low. I use an external pot to adjust the video level.
Turning it has no effect on the horizontal bands.
Adjusting the AGC pot in the tuner doesn't do anything.
The board only loses lock in dark scenes, never bright.
Increasing the video level helps that problem.

It seems like the CD4066 is causing the interference
or it happens after it. I replaced the IC and the PIC ...

This is a Jerrold 5507 PAL-M system.

Thanks.

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