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Date Posted: 06:19:59 12/20/01 Thu
Author: Jain
Subject: Re: Canton 4.2 needs a Coin !!! Read this
In reply to: Jain 's message, "Re: Canton 4.2 needs a Coin !!! Read this" on 06:08:36 12/20/01 Thu

Sorry, Tom is the author of the schematic for AGC fix.
I tested it with a TL084; the capacitor shoud be in the range of 10nF. If used with TLC 08x or TLC262 the capacitor may go down to 100 pF. I guess is enough to sample AGC during Vertical blanking (but using the original capacitor, 1 uF or so, for AGC filter). If I'm not right, let us all know (I made all the test yesterday on the bench, didn't have time to put it in the cable addapter.
Jain

>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.
>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

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Replies:

  • Re: Canton 4.2 - Metal Shield + AGC -- lcs, 21:54:09 12/21/01 Fri
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