2 "real" Gameboards in 1 cab: Hack a KVM switch???

[MameFan]

Here's an interesting though. I wonder if anyone here has tried it.  I am tempted but wanted to see if anyone had an idea if it would work.


First of all, we're talking authentic game boards--not mame or something. I'd like to connect 2 different game boards to the same monitor and control set. (Arkanoid and Arkanoid 2)  

I already have the adaptor convert made (a reverse Jamma converter--I converted the Jamma ARK2 board to be compatable with the ARK 1 proprietary Taito harness), board runs fine.   When I try to connect them both together and only flip the video, I get input ghosting problems (Pressing 1 button causes another one to hit, or they pulse on their own)

I was curious if anyone's tried to hack a digital-based (not knob based) KVM switch to do this?

I was thinking running the 4 wires+ground for the monitor through the VGA connector, and then running the input controls through the keyboard/mouse input (or spare pins on the vga).

They're < $25 after rebates so its a lot cheaper than buying Clay's mutli-Jamma board and converting them all to Jamma (that's $125).


I just don't know if these contain "pure digital relay" switches that work at 5volts, or if they are some type of special circuitry that buffers input between them and wouldn't work as they'd expect a certain protocol/signal rather than just raw wires.


Any other techie guys here wanna comment?

[BobA]

Not sure what each specific model of KVM swich uses for active circuitry.  YMMV depending on the switch.  You could use a parallel port switch that switches all the wires with no active components to switch your jamma cards.

BobA

[Kilgore]

OK it isn't as much fun as building your own but it is on topic:

http://www.multigame.com/jamma.html

[MameFan]

Yeah, as I said, I'd rather hack something for $20 than pay Clay $125 for a 8 port one that I only need 2 ports on.

Actually, I have been doing some reading, and am not ruling out the KVM hack (yet).   However, I read up on the 4053  3 port SPDT analog signal IC.   I can get them for under 50 cents each. Each one sports basically, 3 single pole, double throw relays.  

For my application (Running original arkanoid (Non-Jamma) + arkanoid 2:doh (Jamma) in an upright), I have determined I only need a minimum of 11 lines switched, a maximum of 14.  That only means 4-5 IC's (plus a driving flip/flop IC to pulse the switch and circuit and project board).

Signals needing to be switched: R/G/B/I/Coin/1Left/1Right/1Fire/1Start/2Start/Speaker+ (11)
Optional: Meter/Service/Tilt (3)
For a cocktail, add 3 wires.

Couple that with wires, a 22/44 and a 28/56 se connector, and a 22/44 edgeboard (to connect to existing harness) I can run both games in the same classic arkanoid cabinet with quick switching.

I figure for under $10 in cost, a few hours soldering, I can get an adaptor that MIGHT be of interest to others wanting to run dual Arkanoid. (Anyone else interested?).


I could also use 4052's (6 to 7 of them) to have 4 boards switched. However there is only 1 other Arkanoid board -- Tournament Arkanoid that has different patterns.


Anyway, I havn't decided how to attack this, but it seems like an interesting project none the less. Not much more complicated than making a Proprietary harness to Jamma adaptor (that I already did to play Doh in the classic Ark cab by switching harnesses).

[MrArcade]

Couldn't you just interrupt the grounds going to the board?  I would think this would stop any input probs...or video.  Use a switch to select which pcb gets the ground?

I have not tried this, but it would be my first attempt if I were trying...

[MameFan]

Nope.  I tried that, doesn't work.

I tried both with powering both boards and then without powering both boards.

The problem is that interconnecting the + leads to the input results in phantom problems where the electricity is back-leaking through the components on the other board, causing problems with input.

I had hoped it would be as simple as killing a ground, but so far, at least with the two boards I tried, it does not work that way.  In addition, it seems you may fry something with connecting all the positive inputs together.  Also of course the video needs to be fully switched because otherwise that will leak backwards and result in very dim pictures from the one trying to display, which is the same problem as I'm seeing on the inputs.

[seaner]

I've similarly switched spinners/trackballs in and out using relays and a simple toggle switch to drive the relay.  Running a few multi-pole relays in parallel would probably work out fine for you, only it'll just cost you a few $$ extra.
The KVM switches that I have used did not incorporate mechanical type relays, evidenced by trying to hook 2 keyboards once up to 1 PC through the switch backwards.
You may want to look into something like what I have on my desk right now for switching DB-25 connectors around.
It's a Belkin "data switch"
It has a 4-way switch and 5 DB-25 connectors on the back.
I'm of course only assuming that it switches all 25 conductors.. it may be specially for serial comms, and not also parallel-port type stuff.

[MrArcade]

ummm....how about using some diodes?  they are dirt cheap...and the will stop the current from flowing the wrong way to the unused board...