Space Invaders (M) no controls for P2.

Scucci

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I don't have many friends over that have ANY interest in Space Invaders... So I usually just play a 1 player game. One of the ladies down the street came over a few days ago and wanted to go head to head on Space Invaders... I was player 2, and quickly found out that none of the P2 inputs are working... I didn't even think about it because I assumed that was all handled by the game itself, and not the hardware... ... wrong.

I read a few other posts here about P2 stuff not working, some of the threads were saying it was a voltage issue. I checked my voltage on the board, was at a steady 5.0V. But I had the voltage cranked all the way up on the PS board... so I cleaned some pins and now voltage is 5.16 on the games boards... so, voltage shouldn't be an issue any more.


But, P2 is still dead in the water. I checked the schematics for the Midway Space Invaders, saw there are supposed to be 25S10's for the datashifters on the controls... I have 74151's on my board... I can only assume they're supposed to work the same way. I'm just wondering... how does this work?

Looking at the internals in my "big yellow book", it seems there are just a crap ton of OR gates on D0-D7 running to an AND gate at W and NOT'd at Y?

I'll have to look at it later this evening when I get home from work... but with all of P2's controls dead, it wouldn't make sense for ALL of the 151's to be failed, right?

What would be the next component, the one in charge of handle'ng JUST player 2's stuff?

I can't really trace this stuff out right now because I'm literally on my way out the door to work. Just wondering if any of you 8080 set gurus out there have this stuff memorized and could give me a pointer at where to look next since my boards already don't match up to the schematics?
 
Always check the easy stuff even if it doesn't make sense...

DIPs.

I've looked at the DIPs switch settings several times online.... and NEVER noticed the part at the bottom that say "5,6,7 for UR"... So, yeah... 5, 6, and 7 for UR. Figured since the screen wasn't flipping that I WAS in UR mode... ... wrong.

Apparently my upright is mean, "shorts P1 and P2 input lines together so P2 works as well..."...so, now I know. And I have a thread to prove, yet again, how dumb I am. Go, me.

Thanks, Braze.
 
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