Copyright 2015 Brian Brzezicki, all rights reserved.
Feel free to link to this or use the information within, but please give credit where credit is due.
3/13/2015 - write up version 1.0
3/13/2015 - write up version 1.1, important fix, additional jumper added
3/13/2015 - write up version 1.2, carnival normal (not freeplay) single ROM image added
3/30/2015 - write up version 1.3, new pictures of fabricated board attached. For Carnival troubleshooting info please see the carnival troubleshooting page
This is a write up of a hack to replace the 16 2708 game EPROMs with a single 27128 EPROM, this hack is designed in a way that does not cut or alter (besides 4 empty solder points, the carnival board itself and is completely reversible. To reverse, simply remove the soldered on wires, remove the daughterboard and insert the original ROMS into the correct locations.
This hack should work with any of the Sega VIC/Dual VIC games, as long as you install the proper ROM image
|Remove the 16 2708 ROMS from the carinval game board sockets|
|Take a solder breadboard. Insert 2 12 pin terminal strips in the "parts" side of the breadboard down through to the other side.Make sure the following conditions are met when placing the headers.
|Solder the terminal headers in from the bottom (solder side)|
|Flip the board over to the solder side. on the left side cut the trace beween the top most left pin and the hole to the LEFT of the pin.|
|Turn the board over to the parts side, cut off the terminal strips sticking out on the right side, to make room for the socket that will eventually need to go on.|
|Turn the board back over to the solder side. Count up from the bottom to pin 7,8, and 9. Cut the trace seperating the header pin for 7,8,9 and the hole to the right of each pin.|
|Flip the board to the part side. Count up 7 pins from the right. Solder in a 6" wire into the hole, 2 positions to the right of pin 7 on the right.|
|Solder a jumper wite in the hole below the wire in the previous step to the hole above the wire in the previous step.|
|Solder a jumper wire from the pin to the left of the topmost right terminal pin. to the hole 2 holes above it.|
|From the right side of the terminal strip, count up 9 pins. Solder a white 6" wire 2 holes to the right of that pin.|
|From the right side of the terminal strip, count up 12 pins. Solder a green 6" wire 2 holes to the right of that pin.|
|From the left side of the terminal strip, solder a yellow 6" wire in the hole immediately above the top left pin|
|Solder in a 28 pin socket, lining the bottom of the socket up with the bottom of the terminal strips. Make sure the each side of the socket is to the right of it's corresponding terminal strip..|
|From the right side of the socket, solder a jumper wire from the hole to the right of the top most pin, to the hole immediately beneath it.|
|Burn your specific game single ROM file to a 27128 EPROM.
|solder the correct wires from the daughter board into the solder holes as displayed, using the colors as refereneced in the previous steps|
|Make sure to Remove all the 2708 ROMS if you have not already, then insert the daughter board into any of the empty 16 ROM sockets.|
NOTE ignore the colors of the wires in this picture, they do NOT follow the scheme as I've written it up it is just for illustration
|I just designed a small "clean" pcb board in eagle, and sent it off for fabrication, we will see how it turns out. You can download the eagle layout file here|
|The fabricated board|