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Date Posted: 07:14:06 02/24/02 Sun
Author: Potter
Subject: Re: Experiments on 3chip
In reply to: Jain 's message, "Experiments on 3chip" on 18:26:48 02/23/02 Sat

Hi Jain

Is the greenish colour on scrambled channels due to inverted colour burst, or the decoder expecting an inverted burst and 'correcting' it? Incorrectly inverted burst gave me a blueish picture on a composite monitor. Have you tried changing the connection to the burst gate (4066) to the opposite polarity from the input buffer.

>I was complaining about waves on vertical lines; after
>imagining different scenarios about possible causes it
>seems it's my TV set that doesn't behave great in
>tandem with 3 chip (on a different TV set works quite
>good).
>I guess some time ago Potter was complaining about
>output capacitor (a large value that made problems).
>Actualy, there is no need for a large coupling
>capacitor in 3 chip, nor at the input, nor at the
>output or somewhere else on the path of the signal.
>There is no low frequency passing with the video
>signal (a very reasonable value would be 1 - 2 khz),
>so you can calculate the time constant of every
>coupling RC circuit at around 1 millisecond (I changed
>the 47uF at the imput of Canton 3 input amplifier with
>a 0.1 uF with no difference on the screen).
>I still have a problem with the greenish colour on
>scrambled channels (so the circuit from Canton 5 must
>be tested) and I also would like to have unscrambled
>channels passing through 3 chip without beeing
>decoded; since (I don't know why) there is a
>difference between the signal here and the code (I was
>also complaining about black border -- I noticed that
>here line 23 is an active one) I have to make the
>effort and learn to handle the soft: it's the next
>step before trying any other improvements.
>Overall I'm quite pleased with the results so far. All
>the best to all!
>J

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