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Date Posted: 22:47:13 12/19/01 Wed
Author: lcs
Subject: Canton 4.2 needs a Coin !!! Read this

If you look at my previous messages, I've
been having LOTS of trouble with Canton 4.2
from the beginning, with all kinds of
problems: edge detector, video amp. stage,
unstable lock, dark horizontal bars in
the picture, LBD not working properly, etc...

AT first I thought the circuitry needed fixes
and so I started to build separate modules: VxCO,
video amp, comparitor, the Cd4066 and the video-out
stage. That's when things started to get better,
but it also proved that Canton's circuits had
no problem, apparently. I couldn't prove anything
wrong with them, except for a few adjustments.
(I replaced the power supply, the cable signal, the PIC,
CD4066, Lm393, the tuner, fixed the AGC, tried different codes, added pots to adjust almost everything).

I got to a point where the board was working QUITE OK,
but with an awful picture in what seemed to be an AGC
problem. As i built an entirely new external video amp.,
and the symptoms remained the same, I started to check
the CD4066 and PIC. Trying to solve the "AGC" puzzle,
I noticed that moving my fingers near the PIC had
a definite effect on the picture. I had found an RF
interference coming from the PIC into the CD4066.

To check this out a put a simple coin (metal shield)
on top of the CD4066 and BINGO, the picture got 500%
better!! (PIC 16F84A with 7805 regulator).

I found the PIC being side by side with the other
circuits, this RF interference messes up with almost
everything in the board. That's why my external modules worked better.

I had built everything on the board to the precise specification, including the PCB (which was a real
pain to etch at home using the toner transfer process).

I which i could design a new PCB layout and test it
but unfornately my Protel license just expired...
If someone can do it, I'd suggest you didn't try to
make it so small, and keep the main components
perpendicular and not close together. Make the board
rectangular - not square - and place the video input
and edge detector at one end, and the PIC at the other.
The board being rectangular it would fit perfectly
inside a modern VCR, where there is about 5cm (2") left
to the side of the mechanism.

I noticed Canton 5 is even more difficult to build
and has the same liabilities.

Must apologize to Canton for having criticized his design.
And to Dave2, no hard feelings, please.

Merry Xmas!!

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