Sega G-80 Multigame, Version 1.0
Copyright © 1998, Clay Cowgill
Upgrading the CPU card:
We’ll be removing four chips from the CPU card. They are:
•
U15 – a 16 pin PROM
•
U21 – a 40 pin security chip
•
U25 – a 24 pin 2K EPROM
•
U22 – a 40 pin Z-80 processor (usually U22 is not labeled on the PCB)
Using a small-blade standard screwdriver or chip puller, remove the four chips listed above and place
them in a static-safe area. (Be sure you didn’t bend any pins—if you did, bend them back carefully.)
You can put the EPROM, security chip, and PROM with the EPROM card as we will not need them any
longer.
Take the Multigame Daughtercard and hold it so that the empty 40 pin socket is at the bottom, closest to
you. Carefully place the Z-80 processor you removed from U22 into the socket on the Daughtercard.
Pin one of the Z-80 should be in the lower-left corner and the “notch” of the IC should be on the left-side
of the board like the EPROM above it on the Daughtercard. Press the Z-80 down firmly into the socket.
Make sure you didn’t miss any pins or bend any under.
Take the CPU card and hold it so the “card edge” is closest to you. The red “test” switch should be in
the upper-right hand corner. Take the Daughtercard and orient it so the Z-80 is closest to the red “test”
switch. The three smaller chips on the daughtercard should be closest to you. Make sure the pins on the
daughtercard are lining up with the socket at U22 and firmly press the Daughtercard into the socket. It
should seat with a “chunk” sound. The card should be covering the SRAM’s at U26 - U29. Make sure
all the pins line up and go into the socket.
Take the “G80 Multigame Security Plug” and orient it so the “notch” is facing the Daughtercard. (The
text should be “right-side up” as you look at it. Press it firmly into the empty socket at U21. Make sure
all the pins line up and go into the socket.
U22
U25
U21
U15
