Vector home rom, or how to blast a bally-35 to new memory limits...
I was again in touch with marcel, and I decide to enlarge my custom vector game rom again.
Unfortunately the custom vector game rom is absolute full and the bally-35 can handle only two 2732 Eproms maximum, so the complete program rom size is 8912 bytes (or 8 K). After my nineball experience with the mpu-200, I found an easy way to overcome this limitation of the bally-35 board too.
I built this little adapter and put it in the u2 socket:
With this little adapter, you can use one 27256 eprom instead of the two 2732 eproms. I keep the adapter extremly simple, as a result of my modification the entire game rom size for a bally-35 is only doubled...(16384 bytes (or 16 K)).
Here is how to do it:
First, burn the file on a 27256 (or a 27512) eprom.
vector 10 (*still on betatest)
10 160208 dip switches 17,18,19,20 have new meaning, , coin 3 uses same switches as cooin 2 (dip 1- 8)
17 = on -> Start player one is "Hi I m I pac", start player two is "Welcome to vectordrome"...
17 = off -> Sometimes (50 %) start player one is "Welcome to vectordrome", player two is "Hi I'm I pac"
18 = off -> new skillshoot enables in left inlane for x y z targets (8 6 3 seconds)
18 = on -> no new skillshot
The quote "defender down" is replaced by "stand by for vectorscan" sometimes (50 %)
1) Take a little breadboard and a 28 pin socket (I used a 24 pin socket) for the 27256 and a socket adapter for the U2 socket (looks like this):
2) Cut the traces and solder the socket adapter to the breadboard.
3) Solder the 28 pin socket to the breadboard.
4) Solder one wire from the socket adapter pin 24 to the pin 28. (27256 socket, small red wire upper left)
5) Solder three wires to the 27256 socket (as described to pin 26,27 and 2 from the 27256 socket).
6) Solder one wire from the backside of the socket and connect pin 20 and 22 (27256 socket).
Here a picture from the backside:
7) Insert adapter into u2.
8) Solder the three wires to the backside from the j5 connector
9) Don't forget to modify the jumpers:
10) Here you see the bally-35 on my testbench...
Mail me your feedback...