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Date Posted: 21:54:09 12/21/01 Fri
Author: lcs
Subject: Re: Canton 4.2 - Metal Shield + AGC
In reply to: Jain 's message, "Re: Canton 4.2 needs a Coin !!! Read this" on 06:08:36 12/20/01 Thu

>Thanks lcs! This will help many of those that are
>trying this device.
>Some people having similar problems shoult try to add
>a metallic shield on top of 4066, connected to the
>ground (pin No 7), but be careful not to touch
>something else.

Actually, shielding the 4066 does not "cure" the
board, just improves picture quality. I'd suggest
a modified PBC layout and maybe a metal shield for
the PIC (RF from it contaminates everything), plus
shielded cables for the video input and output, and
maybe the hole board inside a grounded metal box...
[operation Ever Lasting Peace, as Mr.Bush says :) ]

please read on ...

>As I said in a previous message, I had problems with
>the IF IC that didn't handle too well the lack of
>Hsync (even it had a 100uF capacitor at the AGC pin).
>My temporary solution (proven to be effective) was to
>add a pot (2Mohms) between +12V and ground and the
>cursor to the AGC pin, adjusting it to be in the
>middle of the voltage range when sweeping unscrambled
>channels. AGC sample and hold (Potter's schematic) is
>the right solution.
> Jain.


My VCR has a LA7530N as VIF and SIF detector. It uses
a 10k pot to adjust the RF AGC and a 10uF cap at the
RF AGC OUT. I haven't had to play with them yet. The
IC's datasheet can be found at the semiconductors
page of Sanyo, in Japan. (www.sanyosemic.jp, I think).

PS: the LA7530N outputs 2Vpp video but the tuner
reduces it to much less --not enough to trigger
the edge detectors. So I opened up the tuner and
inserted a transistor (emitter-follower) to capture
the good video without modifying the original circuitry,
except that the descrambled video from the 3c is
fed into the next IC in the VCR, thus solving the
Blue Screen problem. Even with this mod., I noticed
the video signal must come to the 3c via shielded cable
or else it will get RF interference.

lcs

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