PCB Repair Logs Neo Geo 4 Slot

Neo Geo 4 Slot

Neo Geo 4 Slot

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Pin Out	Reserved

Board 1

Repairer: raysco
Forum Thread: Neo Geo 4 Slot PCB Repair

I bought this the other day, it would only boot to the "crosshatch of death" although all diagnostic functions worked. It just wouldn't see any cartridges. I stripped the top board off and had a good look at the bottom board.



Just around the battery i could see green/blue dusty fragments, there was corrosion around CN10 under the battery.



I spent a couple of hours doing pin continuity checks and finally took a chance on where the three missing tracks were going. I could have saved myself some time by doing a search on the net, as after I finished my repair I found the info I needed.....Typical

There were 3 missing tracks that had been corroded through so I put jumpers across them, (Probably need thinner wire but this was all I had on a Sunday)



It may not look that pretty but this is the final result,



I still have a few glitches with the cartridges but I think thats down to a clean of the connectors as if I tap them I can get glitchy graphics but that clears with another tap.

Very, Very happy with my days work

Board 2 MV-4FT2

Repairer: RetroRepair
Forum Thread: Neo Geo 4 Slot PCB Repair

Symptom: Background/Foreground/Sprite graphics missing, sometimes come back partially, sometimes fully. When fully working, always dissappear again after a few seconds having swapped to slot 2. Text always worked. Battery had leaked at some point and was removed before I got it.

Solution:This one had me confused for a while.

The problem was intermittent. Sometimes after being left on for a bit then turned off and on everything came back. When the game in slot two came up though, it'd always dissappear after about 30 seconds. Not all at once, gradually.

My first thought was to check for gouged traces as ever. Though it doesn't make much sense, I've had similar issues with broken traces, intermittent too. I found none.

Next port of call was to double check the traces around the battery damage. I also found no problems there.

Next I decided since it was almost certainly an addressing issue before the RAM (usual when there are no RAM errors) so I checked the often problematic LS245s around the top board connectors on the bottom board. All seemed to be doing as they should.

I got fed up and checked up on channelmaniac's excellent logs on the newlifegames forums: http://newlifegames.net/nlg/index.php?board=19.0

One post in particular caught my eye about the NEO-ZMC2 IC which apparently is a graphics data multiplexer. He had an issue with a 4F which was very similar to mine and there were at least two lines bridged by solder. So I checked mine out and though I found no solder bridging, I did notice it didn't look like it was soldered very well so I decided it couldn't hurt to give it a reflow and everything instantly came back!

I let it run through the attract on all 4 slots for an hour, turning off and on for 2-3 mins at random intervals then had a few games on SS2.

Symptom: Unibios throwing up a selftest error at boot in "The System BIOS". System functions normally after skipping the error.

Solution: Burned a new Unibios and tested. Was a bad Unibios!

Seems like this one's good to go

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