Ok, first things first -- this is not my first repair, but I thought I should start with a repair log of something unusual.
Neo Geo MVS carts are not usually something that one would repair, since most games are relatively affordable and as such are easily replaced. On the other hand, these repairs are usually somewhat trivial, requiring just track repair, maskrom replacement, solder touch up or if you're unlucky, the replacement of one of SNK's custom chips.
This one however was not such a case.
The game I was sent -- SvC Chaos -- was one of the last games published for the MVS. The cart has an unique PROG board with a custom that only exists on it, the NEO-PVC. This chip basically serves as copy protection and without it, the game does not work at all.
I was sent this cart for repair with the quite accurate description of it not working and that it had happened suddenly. Indeed, it was the case, displaying a blank screen upon booting. Or more accurately, not booting at all. Pressing the 1P start button I could flip between screens. I was actually stuck on the hardware test.
I opened the cartridge and did a visual inspection. It was impeccable. No track rot, no bad solder jobs, no obvious signs of damage whatsoever, bar a minor bump on one of the capacitors inside.
Without much to go on, I decided to tackle what I believed to be the root cause of the problem, a failing or failed NEO-PVC chip. The soldering on it seemed solid, but I decided to reflow it just to be sure.
After carefully and slowly reflowing the chip with no-clean flux I tried the game again and... nothing. No change.
Some cursing ensued.
I evaluated my options and the transistor like device in the middle of the PROG board caught my eye. I remembered that later MVS games used 64 megabit ROMs which I found odd.
"Maybe they're just flash ROMs in a different package. What if they're 3.3v parts? Maybe the NEO-PVC is actually 3.3v and it's not getting any power!"
After checking that the 48M033F was a voltage regulator -- it was! -- I decided to probe the P1 ROM with my multimeter set to continuity to check whether it was connected to the voltage regulator. That's when something odd happened. Both Vcc and GND beeped on the exact same pin. I checked the voltage regulator and it was shorted. A quick prod to the capacitor to its right and I had found the culprit. The slightly dented capacitor was shorted too.
I removed the capacitor and checked the voltage regulator and found no more short. I replaced the capacitor with an equivalent through hole part and tested the game. Success!
The game is now back to its owner and being enjoyed once again.
See you next time!
ic3b4ll
Neo Geo MVS carts are not usually something that one would repair, since most games are relatively affordable and as such are easily replaced. On the other hand, these repairs are usually somewhat trivial, requiring just track repair, maskrom replacement, solder touch up or if you're unlucky, the replacement of one of SNK's custom chips.
This one however was not such a case.
 |
| The patient. |
I was sent this cart for repair with the quite accurate description of it not working and that it had happened suddenly. Indeed, it was the case, displaying a blank screen upon booting. Or more accurately, not booting at all. Pressing the 1P start button I could flip between screens. I was actually stuck on the hardware test.
I opened the cartridge and did a visual inspection. It was impeccable. No track rot, no bad solder jobs, no obvious signs of damage whatsoever, bar a minor bump on one of the capacitors inside.
Without much to go on, I decided to tackle what I believed to be the root cause of the problem, a failing or failed NEO-PVC chip. The soldering on it seemed solid, but I decided to reflow it just to be sure.
 |
| The NEO-PVC post reflow. Yes, I cleaned it afterwards. |
After carefully and slowly reflowing the chip with no-clean flux I tried the game again and... nothing. No change.
Some cursing ensued.
I evaluated my options and the transistor like device in the middle of the PROG board caught my eye. I remembered that later MVS games used 64 megabit ROMs which I found odd.
"Maybe they're just flash ROMs in a different package. What if they're 3.3v parts? Maybe the NEO-PVC is actually 3.3v and it's not getting any power!"
 |
| Weird board, ain't it? The M48F033 voltage regulator is the black transistor like thing in the middle. |
After checking that the 48M033F was a voltage regulator -- it was! -- I decided to probe the P1 ROM with my multimeter set to continuity to check whether it was connected to the voltage regulator. That's when something odd happened. Both Vcc and GND beeped on the exact same pin. I checked the voltage regulator and it was shorted. A quick prod to the capacitor to its right and I had found the culprit. The slightly dented capacitor was shorted too.
 |
| The fix, nice and easy once you figure it out. The capacitor to the right is the replacement (Duh!) |
I removed the capacitor and checked the voltage regulator and found no more short. I replaced the capacitor with an equivalent through hole part and tested the game. Success!
 |
| It's alive! |
The game is now back to its owner and being enjoyed once again.
See you next time!
ic3b4ll
Nice repair log. Keep the good job.
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