Re: Question about Clay's multigame

>I guess this is primarily directed towards Clay, but others may have a
>little input...
>
>Anyway, I was wondering if you could add a little circuit to your
>daughtercard to eliminate having to hook up that 3VAC (I think) to the G80
>system. This would totally eliminate that flaky power supply and would
>make the mess under my ST cockpit seat a lot neater :)!!!! I read in the
>Sega XY FAQ that a 555 may work as a viable sub for that stupid 3VAC. I'd
>try it out, but I doubt I have the time right now between school and work.
>I hate to bring up ideas and let others try them at the expense of their
>time, but this would benefit all if it does work. How does this sound?
>What I could do is get the values needed for the 555. I guess all we'd
>need is a square wave with a Vpp of 6V running at 60Hz. If others do not
>want this feature, It could be bypassed with a jumper. No big engineering
>feat, I know :). Oh well, take care and have fun!!!!
You're actually talking baout two different things here. The 3VAC is only
required to keep the Z-80 from reseting. The whole idea Sega had behind
this was that they found a quick power on/off would sometimes credit the
game. The 3VAC guaranteed a reset CPU on powerdown/up.

The really annoying thing is that the coining circuit requires a 1ms pulse
to actually coin the game. This was another of Sega's ideas to reduce
the chances of someone tripping a free credit any other way than with a
coin.

Here's a simple 555 timer circuit that will let you use a regular
Jamma-type
low signal to coin the game (you can also use the service switch but this
doesn't help for 4-player Eliminator):

Sega Coin Hack
--------------
Paul Tonizzo (tonizzo@sybase.com OR aq929@torfree.net)

This hack is used to defeat the idiotic coining mechanism on Sega's
G-80 games.

The basics are that the circuit uses a 555 timer to generate a clock
pulse. The pulse itself is low for ~1ms and then high for ~1ms
and repeats itself (1ms was the optimal value for the pulse width
to get the coin to trigger). The circuit itself is not at all unlike the
rapid
fire circuit for some Midway games (but it has been greatly simplified.)

Here's all you need to build it:
Qty Desc
--- ----
1 555 timer chip (8-pin)
1 8-pin socket (for the 555)
2 0.1 uF capacitor (use mylar caps)
2 1 Meg ohm resistor

You should be able to use a really small piece of perfboard to make this.
(1-1/2" square would do it.)

Wire it up as follows:
- pins 4 and 8 of socket to +5v
- one side of first 1M resistor to +5v, other side to pin 7 of socket
- one side of second 1M resistor to pin 7 of socket, other side to pins 2
and 6 of socket
- one side of first 0.1 uF cap to pin 5 of socket, other side to pin 1 of
socket
- one side of second 0.1 uF cap to pin 2 of socket, other side to pin 1 of
socket
- pin 1 of socket to pin 5 on G-80 CPU board
- pin 3 of socket to pin 6 on G-80 CPU board

For all games except 4-player Eliminator:
- pin 1 of socket goes to coin or a coining button of some kind

For 4-player Eliminator:
- you also require 4 general purpose diodes (1N4001 will do)
- take all 4 diodes and the ends closest to the black line should all
be tied together (this is the end the electrons CAN flow to). These ends
then get attached to pin 1 of the socket
- the other ends of the four diodes should go to the coining buttons (one
for each player)
- the coining buttons also go to pins 2-5 on the i/o board.
- the only other thing that changes on the i/o board is that the board
outputs that go to pins 5 and 6 on the G-80 CPU board should be cut.
Received on Wed Nov 19 04:46:09 1997