Neo-Geo 4 Slot Issue (bank switching)

tandrews_ny

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I have a Neo-Geo 4Slot and I'm getting issues with games that use bank switching.

https://youtu.be/PIetfcOdI3g

Two games I have it occurs with are Sam Shodown 4 and Metal Slug X.

It occurs on all slots.

Here is a final check list of all I've done:
* Flashed to Unibios and checked the roms, see attached pictures
* Cleaned the carts and edge connectors real well (contact cleaner)
* Cleaned the board to board connectors
* Verified voltage @ the harness and PS
* Verified cartridges worked on another Neo Geo (1slot)
* Checked internal battery
* Cleared work ram.
* Verified the PORTWEL line goes low (or is it high?)

I do have a logic probe (Saelea[sic]) and a reagol scope if I need to probe anything.
 

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Do you have other carts you ca test in there. I know the four slots can be finicky. Might want to drop Channelmaniac a line. He is a Neo guru.
 
Sounds like you have a signal missing. Start with the basics.

Gouged trace
Battery damage
Corrosion damage on top board (liquid and/or rodent)
Corrosion damage under top board (bad foam/adhesive on bottom side)

Give the board a good stink eye look for any gouged traces and check continuity on them. Carefully check around the slots and chips on the top board for corrosion damage.

It's pretty rare for a chip to fail on the top board. It's usually dirty slots, gouged traces, or corrosion damage.
 
Sounds like you have a signal missing. Start with the basics.

Gouged trace
Battery damage
Corrosion damage on top board (liquid and/or rodent)
Corrosion damage under top board (bad foam/adhesive on bottom side)

Give the board a good stink eye look for any gouged traces and check continuity on them. Carefully check around the slots and chips on the top board for corrosion damage.

It's pretty rare for a chip to fail on the top board. It's usually dirty slots, gouged traces, or corrosion damage.

Crazy thing is, they both worked when I first got them. The next time I went to play, they didn't. I've done all of that, I literally am out of ideas. The boards looks amazing. I've cleared the contacts with constant clear. I don't know what else to do...
 
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