TECH: Stern or Sega Whitestar board info
- From: Eric A. <eavedesian@xxxxxxxxxxx>
- Date: Sun, 07 May 2006 13:41:27 -0400
I figured I would post this for the Google records since there doesn't
seem to be any info ANYWHERE! :-)
There are 2 leds on the CPU/Sound board. The top one is for the
+5volts and the bottom is the one that tells us the CPU section is up
and running.
If the bottom led blinks twice over and over it means that the Eprom
has a problem. In other words the program can't run. In my case it was
trying to run CPU version 1.03 with .90 sound roms. Additionally it
seems that the original sound roms were left in the game with some
later CPU revisions such as 1.01. I'm not 100% sure on this but it
appears that there was a later run of the CPU that still used the old
sound roms.
Next, the I/O board has a reset chip on it also. It is a DS1232 this
monitors your +5 volts and makes sure it is getting a valid signal
from the CPU. Actually, it comes from pin 19 on U6 of the driver board
but the input to that chip comes from the CPU. The led that is
associated with this is L204 on the upper right hand side of the I/O
board. The ribbon cable caries this signal from the CPU to the I/O
board. If the led is blinking this board is constantly resetting. You
should get 1 or 2 blinks when you first power up the game but then it
should stay on.
With a logic probe, you can verify the signals on the DS1232 chip. Pin
8 is +5 and should be high on your probe and pins 2,3,4 should be low
or ground. I know in the schematics it shows that there is no
connection to pin 3 but physically it IS attached to ground. First you
need to see pin 1 go high and stay there. If it does not you have a
problem with one of the associated chips shorting to ground or one of
the resistors (269 or 271) is open or has a cracked solder pad or the
+5 itself is low or dropping in and out.
Next, look for that stroking signal I was talking about on pin 7 of
the Dallas chip. if that is not there then look for the input signals
on U6 pins 3,4,7,8,13,14,17,18. Also, you need the LMPSTB signal to be
pulsing on pin 11 of U6 and the NOT RESET signal to be high on pin 1.
However, until this board comes up and starts running the NOT Reset
line will alternate between high and low. If any of these are not
there then trace back in the circuit and find out where it is
stopping.
On my game the Dallas chip and a few others were bad but this is where
it was staring from. Without the led coming on and staying on the
solenoids and lights will not work.
Hope this helps someone down the road.
Eric A.
313-268-0541
"Mr. Propane Torch"
.
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