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Neogeo MVS MV-1C YSA2 broken input

tiff_lee

tiff_lee

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Hi all,

so i've got a MV-1C board and the A button input for player 1 is U/S, the circuit is good all the way to the NEO-YSA2 chip but since there is no pinout available (or schematic) online for the MV-1C I can only assume at this point the output of said chip is bad.

Can anyone enlighten me as to what the YSA2 actually does with the player input? According to:

https://wiki.neogeodev.org/index.php?title=NEO-YSA2

the YSA2 is a combination of the YM2610 and Z80 which are both related to sound playback so what does it have to do with player input?

From googling I can also see this chip is a common failure point on the MV-1C, someone on the neogeo forum came up with a workaround for a 'stuck' input (am I allowed to mention or link to that forum...?)

http://www.neo-geo.com/forums/showthread.php?274310-Fixing-stuck-inputs-on-MV-1C

again without a schematic i'm not too sure what's really going on here, it looks like the addition of a74HCT244/5 is circumventing the YSA2 and going straight to the 68K? if the 68K actually deals with player input why goto the YSA2 in the first place?

Edit:Totally made this in the wrong forum section, reported for a mod to move as I am unable to delete
 
No neogeo gurus on here who can elaborate a little on this?

I've already wrote my board off and have a functioning replacement but ii'm still curious as to what the custom YSA2 does with the controller input and how using the additional chip fixes a stuck controller input.
 
ysa2 repair.PNG
 
@TSMD keep trying with the neo-geo forum account, sometimes it takes multiple attempts.

Those HCT245 /244 are buffers, meaning they keep the signal stable (look up "fan out for ICs" for details).

If you look at the IC pin out, the right side has the inputs (P1.. P2..), the direction of the arrow show that.

The schematics @ack has shared shows that the output goes straight to D0 - D15 of the 68k.

The YSA2 is a late IC generation, IIRC the last one, also used on the NGCD, trying to get another MV1C might be cheaper than a NeoGeo CD, hard to say if its worth it.
 
I have tons of “for parts” MV1C boards that I’d be willing to send for part harvesting with clear gouges and broken PCB sections. Let me know if you are interested, I can look for one with a clean looking YSA2 if you want to try.
 
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Man that would be awesome, but I think that shipping to Mexico would be too expensive, let me try to fix it with the 74HCT245, I am still waiting for it to arrive to test, if I can't fix it maybe I could transfer you the shipping fee via paypal or something, I have a brother living in Texas, maybe cheaper to ship there.
 
So, I had my doubts on how it was supposed to work, but I can confirm now that the diagram is correct, it did fix my MVS, my up input now works as intended.
 
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