Re: G08 custom chip - interesting

Hi all,

I just tried this solution in another monitor in another game (Star Trek).
Since Star Trek doesn't really have any "borders" around the screen, the
picture looks nearly correct. Tac/Scan and Space Fury games may also
because of the lack of borders, but Eliminator and Zektor games look the
worst. YMMV.

Also, this pseudo-fix has only been tested for the past hour, so I have no
idea of how well this "solution" holds up in the long run.

----- Original Message -----
From: "Mark Jenison" <jenison@enteract.com>
To: <vectorlist@synthcom.com>
Sent: Wednesday, July 31, 2002 10:36 PM
Subject: VECTOR: G08 custom chip - interesting

> Hi all,
>
> Well, I'm *really* interested in finding a solution for bad G08 deflection
> board custom chips, so I did some experimenting this evening...
>
> The symptoms of the board are that the Y deflection likes to sit at the
max
> voltage output to the coil(+60VDC). All the rest of the Y circuit has
been
> confirmed fine.
>
> Turns out that in my particular case, I have a chip whose Y analog input
> (pin 11) says "screw the Y input!"...basically something internally has
gone
> haywire. As soon as you connect the Y input to it, the Y circuit output
> (pin 18) goes to like 5.68VDC and stays there, which of course the Y
circuit
> doesn't really like. And even though the Y input likes to be +/-3VDC, pin
> 11 stays around -5VDC when connected.
>
> So I bent pin 11 out of the socket to take measurements on it and found
that
> it was at -7VDC. Just for fun, I measured the output at pin 18...and it
was
> moving! So I measured the outputs to the deflection transistors...and
they
> looked halfway decent. So I hooked up the deflection transistors (no yoke
> connected all this time) and read the outputs to the Y yoke...and they
> looked halfway decent, too.
>
> So I took a chance and hooked up the yoke and got this:
>
> http://www.enteract.com/~jenison/pics/badchip.jpg
>
> As you can see, the picture is sort of key stoned, compressed at the right
> side, and slightly rotated to the left (if you look at the pic, you can
see
> the right side of the chassis for a vertical reference point).
>
> Ok, so the picture is no where near optimal, but it's better than nothing!
>
> Plus, if gives me a little insight as to how the chip works and what
inputs
> do what. At least I have a test monitor again :-)
>
> --
> Mark Jenison
>
>
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Received on Wed Jul 31 21:31:14 2002