Re: Tech: G08 Color Controls

The cutoff pots are for setting black level (cutoff) of the CRT. These
are WAY easier to set on a raster monitor, but the idea is you set the
cutoff pots full CCW and the 3 gain pots to center. Then you adjust the
screen (also sometimes called grid 2 or brightness) pot on the flyback
until things that should be black (the raster on a raster monitor or the
normally blanked retrace lines/center dot on a vector monitor) just
barely disappear. Then you set the other cutoff pots so their
corresponding colors just disappear.

The gain pots are then adjusted so something that should be bright white
IS white and not some other color.

BUT BE CAREFUL. A center dot with any brightness about it will cause
damage to the phosphor coating. And this can happen VERY quickly.

If all you have is blue, you might try feeding all three color inputs to
the monitor with the blue signal. You should then have a black and
white display (if the monitor is good and properly adjusted). If you DO
have a black and white display the game board wasn't putting out any red
or green. If you DON'T get black and white (still only blue) you have a
monitor problem.

Tim Tewalt wrote:
>
> First time at resurrecting a Sega G80 (Star Trek) so please
> bear with me... I just finished rebuilding the monitor and
> see only blue traces.
>
> What are the functions of the "cutoff" pots for red and green
> on the neckboard? I futzed with both the "cutoff" and "gain"
> pots a bit, but didn't get the other colors. I didn't touch
> up the solder joints on these pots yet, but they look good.
>
> Where is pin one on the little input driver board on the back
> of the monitor? Plugging it in one way (what I thought was the
> correct way) I could read the STAR TREK logo (in blue). Plugging
> it in what I presumed to be the wrong way showed a multicolored
> indeterminable mess around the center section of the screen.
>
> I'm thinking the next step will be to go into selftest mode, test
> 6 (screen test) and measure the input levels from the xy control
> board.
>
> Any hints or tips would be appreciated. I think I'll stay
> after work tonight and see if I can finish it up.
>
> Thanks,
>
> Tim
>
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Received on Fri Jan 25 00:47:23 2002