Rasterlist Archives: Re: Space Invaders Tilt error

From: Chris Loggans <cloggans_at_yahoo.com>
Date: Fri May 25 2012 - 18:02:20 EDT

Kevin,

I went through the same thing and if your schematics are like mine, they don't show where the tilt switch is connected. I ended up tracing it out at one point and here is what I found:

The tilt switch input comes in on pin 4 of the right hand connector of the sound board. It goes through a resistor and capacitor like all other switch inputs and terminates at pin 5 of B2. It then goes out on pin 6 of B2 and connects to pin 4 of B3. The schematics incorrectly show that pin 4 on B3 is connected to the +5 volt line that is pulling up all port 0 (P0x) inputs, but it is not. B3 is a multiplexer that puts the status of the tilt switch on the MX buss when the port 2 inputs are probed. If there was a problem with the MX buss, your game would probably be dead so you shouldn't need to look any further than B3. Hopefully that gives you a good place to start looking.

Good luck,
-Chris

--- On Mon, 5/21/12, Kevin Moore <talon.k@gmail.com> wrote:

From: Kevin Moore <talon.k@gmail.com>
Subject: RASTER: Space Invaders Tilt error
To: rasterlist@vectorlist.org
Date: Monday, May 21, 2012, 12:35 PM

I know I've seen this solution somewhere but for the life of me I cannot find it. Got a SI that's showing title error. The schematics don't show a tilt circuit so I'm guessing it was not implemented. Power Supply good, cab good as I've swapped board sets and no problem there.
I'm betting there is either a shorted trace or chip on the motherboard, just not sure where to start looking.
Thanks
Kevin

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