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bodgit

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I have a C2 board that I've realised some of the player 1 inputs aren't working; namely the right direction and button 2. I've buzzed through from what I think are the correct fingers on the JAMMA edge to the pins on the 315-5296 I/O chip; both signals just pass through FLT34 or 38 and then both go through DA1, DA2 and RA4. Here's a diagram annotated with what I figured out:
IMG_2713.jpg

Once I hit the I/O chip I was a bit stumped, and figured if that's the problem then I'm screwed. However on a hunch I tested the RA4 resistor array and the values are all over the place. Here's a closeup of RA4:
IMG_2714.jpg

It's marked 102 so I'm assuming that's a 1KΩ array but I barely measure 650Ω on most of the resistors. Most importantly though, the two resistors I traced through I measure 12Ω and 90Ω (there's one other resistor in the array that measures 170Ω but I'm not sure what input that belongs to, nothing else appeared faulty on the input test in the service menu). The common pin on the array is tied to the +5V rail so I'm assuming this is being used for pullups.

Would this array being faulty be the likely cause of the two missing inputs? If someone could check my workings out, that would be appreciated!
 

Apocalypse

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Hi,

From my experience it's almost always the 315-5296 custom chip (failing internally with a low resistance on input pins), but it's quite easy to pull the resistor array and check, who knows?
The good news is that custom chip seems easy enough to reproduce using latches and buffers.
 

MoppelTheWhale

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if somebody ever make a repro of this - i would need one as well...
 

bodgit

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From my experience it's almost always the 315-5296 custom chip (failing internally with a low resistance on input pins), but it's quite easy to pull the resistor array and check, who knows?
The good news is that custom chip seems easy enough to reproduce using latches and buffers.
I pulled the resistor array and every resistor now measures close to 1KΩ so it does look like it's the I/O chip at fault. Guess I'm also interested in a repro then unless I can find a replacement.
 

Catzoo

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I have the very same issue, and got to the same diagnostic after removing the RA, so i'm really interested in any solution that might help.

While i was working on this, i've had the idea of swapping the input physically to working one (with a custom jamma edge connector) in combination with a romhack that could swap input.

Is it even possible ? I don't have the skill to do such rom modification, but i wonder if it's possible, since the games are decrypted and checksum routines are well known ?
 
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