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Date Posted: 06:27:22 08/25/02 Sun
Author: Potter
Subject: Re: inversion only
In reply to: da_dude 's message, "inversion only" on 07:54:24 08/24/02 Sat

7404 is a TTL hex inverter and definitely won't work on composite video. If you can watch a stable inverted signal then the sync pulses are not inverted but the colour burst may be inverted along with the active video. You still need to 'lock' to the signal to accurately invert only the correct sections.
The inverter can be as simple as a single transistor stage but needs some 'smarts' to do the job properly. In your case (too good to be true or last) a circuit based on a sync separator chip like LM1881 could be successful - look for macrovision decoder designs and the LM1881 data sheet for ideas as well as the 3chip designs in the links.

>System over here is only inverted video - yeah i know
>it seems too good to be true..
>
>I can tune all 30 channels in on the tv but all the
>color is negative. Which circuit should i try and
>will a single chip 7404 invertor do the job.
>
>I heard this may work but it seems a bit simple.
>
>Any one have any advice?

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