Re: incorporating a pause button option,

Sega monitors blow up because the ground reference for the monitor drifts
relative to the logic boards when the power supply connections overheat.
This will then bias the input signals off-set enough to overdrive the
outputs. Hence my argument for chucking the original power supply and
putting in a switching supply. I started doing that about ten years ago and
have not lost a single Electrohome/Sega monitor since. I suspect it also
kills Tempest monitors etc. Those pesky grounds get a few ohms resistance
and all sorts of nasty things happen.

I first discovered this on Gottlieb pinballs over ten years ago-the ground
for the regulator would overheat the pin/wiper contact which would become a
small resistor and thus the ground of the MPU would drift up relative to
the cabinet ground, which also happened to be the ground path for the
driver transistors. When the MPU ground would change to about 0.5 to 0.7VDC
above cabinet ground the base of the transistors would then start to
conduct as the MPU would be trying to turn off the transistors, but the
Emitters are tied to the cabinet ground. Hence the transistors would start
to conduct... You will recall that transistors generate far more heat when
they are used at the beginning of their working range rather when they are
switched completely on and off as in regular vector monitors (or solenoid
drivers, etc.). So in a little while, it croaks. No obvious cause...replace
the transistors and everything works. For now...

So get VERY GOOD GROUND (COMMON) CONNECTIONS BETWEEN THE MONITOR, MPU AND
POWER SUPPLY for reliability!!!!!!!!!!!!!!!!!!!!!!!! Solder fat conductors
with nasty heavy gauge connectors between each component in the
system. Put in healthy SWITCHING SUPPLIES!

Happy vectors will result.

John :-#)#

At 12:05 AM 10/22/01, you wrote:
>On the 6502 it would be the READy line.
>
>BUT, all that will get you is a watchdog reset a few milliseconds
>later. On Pacman the pause switch also stopped the watchdog.
>
>On a vector game pause might cause damage. Don't the Sega games blow up
>monitors if held in reset?
>
>
>John Robertson wrote:....

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Received on Mon Oct 22 01:02:49 2001