I was quite scared about the possibility my Williams boardset could fall while people was playing.
So I decided to plug in the (famous) 19-in-1 board, because I could see the game is very well emulated. But just see and not play, because once I received the board I discovered in half a minute that BUTTON 5 (S5) is supported by software but not by hardware (actually button 5 and 6 for both players). This button is needed because corresponds to the HYPERSPACE button.
Setup shows both buttons 5 and 6, it means who wrote the sw wanted to use them and probably he allocated in the right way the specific resources.
Backtracking all inputs I could see all of them arrive to the 74244 close to the JAMMA connector, with the exception of P1S5, P1S6, P2S5, P2S6.
There are 5 74244 and I discovered that S6 for both players are anyway connected to these buffers but part of the the pull-up circuit misses (and the connection to the JAMMA of course). On the contrary no way to intercept S5.
So I moved to the bus tranceivers (74245) between RAM and FLASH. If buttons are managed, they are managed there (!!)
Playing a little bit with +5 power and using my finger I could change the status of P1S5 and P2S5. This means that S5 signals are undetermined.
Using a pin (pulled up with a wire connected to the pull-up pin of JP1) I touched the pins waiting for a reaction related to the involved buttons and the PIN 3 of U22 (one of the two 74245) was what I was looking for. So I had to start from there.
First of all I connected a wire to the data-bus on the PIN3 of U22
Then I used a 74244 to complete the circuit.
PIN 10 to JAMMA ground
PIN 20 to JAMMA +5V
PIN 16 to the databus
PIN 4 to JAMMA Component side PIN 26 and to a 10K resistor; this resistor then is connected to +5V
PIN 1 to PIN1 of U30; in fact this board uses 4 different signals to enable the input drivers and I tried with the one dedicated to PLAYER1 and his buttons. Just a try.
I’m sorry I haven’t any tool to manage SMD components and boards so my soldering is very bad.
Anyway this is the result:
fixed with some hot glue
It works great and now I have a good board backup 😀
PS reading this post I can see my English is very bad; I’m sorry for that. If you have any question please don’t hesitate to contact me.