Star Tech Journal

STAR*TEcH
Journal
CID
April 1996
SEGA PINBALL WHITE STAR SYSTEM
1/0 POWER DRIVER BOARD THEORY OF OPERATION
(PART Two)
Team Sega
Joe Blackwood, Eric Winston,Jay Alfer, Ted Kilpin
Sega Pinball, Melrose Park, Illinois
I Reset Circuitry U210: I
The 1/0 Power Driver Board will reset in three cases:
1. The CPU Board is in reset The CPU's reset signal is fed into the 1/0 Power Driver Board through
Connector Jl and forces the I/ 0 Power Driver Board into reset.
2. The 5V supply has fallen bellow 4.75V.
3. The watchdog is not being fed by the scanning of the light matrix. More specifically Pin-19 of U6 must
be toggling once every 50ms to prevent the watchdog from resetting.
The scanning of the Light Matrix
is controlled by the CPU through
Connector Jl. LED L204 shows
the reset state of the 1/0 Power
Driver Board.
If this LED is not lit either the
5VDC is below 4.75V or the
CPU Board is holding the 1/0
Power Driver Board in reset.
If the LED is flashing this means
that the watchdog is not being
feed by the CPU Board and the
1/0 Power Driver Board is os-
cillating into and out of reset.
If the LED is continuously on the
board is out of reset and comrnu-
nication from the CPU to the
Lamp Matrix is confirmed.
Address Decoding U204 &
U205:
Testpoint Blanking is the actual
reset signal on the 1/0 Power
All Address decoding is done
by two 74LS138 ICs (3 of 8 de-
Driver Board Board.
coder). Both of these must be in
operation for 1/0 Power Driver
Board to function properly.
A low voltage indicates that it is
in reset, this will tum off all Sole-
noid Drivers, F1ash Lamps, Lamp
Matrix Drivers,
I Auxiliary In & Out: U203
J2 8 CMOS Outputs sometimes
Auxiliary Outputs and Flipper
Outputs. A high voltage indi-
cates that it is out of reset and
normal operation can take place.
used for a printer interface.
J3 8 CMOS Inputs general pur-
pose inputs.
NEXT MONrH: m will take a look at Solenoid, Flash Lamp &
Switched Illumination Drive Circuits.