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Date Posted: 20:17:34 12/14/01 Fri
Author: lcs
Subject: Re: re: Instability
In reply to: Phil Q. 's message, "re: Instability" on 12:27:42 12/14/01 Fri

Phil,

i really had a lot of trouble (Canton 4.2 will not lock)
until undoing the mod. Right now the board loses sync
in some channels when the picture is dark, but not often.

I was thinking maybe I can try with a couple of 2k2 res.,
but this is going to wait until a verify some changes in the
code I'm testing (PAL-M here).

I'm building another board (Piu) and will see how it behaves. Found out Canton 4.2 should have a higher bandwidth in the first stage of the video amp. Picture
quality is lacking (i've double checked the cicuitry).

Bye.

lcs

>You are the first person who has reported any trouble
>with this, everyone else (who has posted) has posted
>good results. The mod does not increase the gain of
>any signal at all, rather it REDUCES the reference
>voltage supplied to the comparator, thereby making it
>more sensitive. I have found that mine will very
>occasionally false on high contrast pictures however,
>so if it seems overly sensitive, try something in
>between, like 3.3K. Changing the resistor and/or
>capacitor values that make up the rc high pass filter
>into the comparator in concert with the reference
>voltage would probably make for a better modification.
> I did the math on this a while back and plan on doing
>it eventually, but until I see it working perfectly on
>my board I'm not going to post any values.
>
>- Phil

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