KoshiroKazuma
Student
Really good topic!
I also met this kind of bad U2 NAND issue on a CV-1000D board.
It's a long story.
I bid one issue DDP-SDOJ board on Yahoo Auction 2 years ago at a low price. The seller described that the game almost 100% freezes at character selection. There was little chance that the game could be played through.
I did some test after i received it. The game would randomly hang when playing demo. And it would 100% freeze after selecting any of the 3 characters. I reboot the board many times and only 1 time i could play through the game without any issue. I didn't find any graphic glitch in game, either.
I checked the board under microscope, nothing abnormal.
At first, I thought there might be some problem with the DRAM chips on board.
I bought brand new DRAM chips and replaced them all on board, but the issue was still there.
I didn't have a clue where the problem really comes from.
Then I thought if there was any data corruption in the NOR and NAND chips. But there was no SDOJ game rom available on internet at that time.
I temporarily give up repairing this board and kept it in the drawer.
By chance, i got another good CV-1000D board this year. I decided to continue repairing the issue DDP-SDOJ board.
I did a swap test , I moved the 4 SDOJ rom chips to the good CV-1000D board, and the same issue was still there. So I could confirm there was data corruption in any of the 4 chips.
DDP-SDOJ mame rom is now available on internet. I downloaded a copy and tried to burn the data into new NAND/NOR chips with a NAND programmer.
I first burned U2 chip and did a quick test. The game was OK and could be played through without issue.
So moved the rom chips back to the original CV-1000D PCB. Yeah! It's completely back to normal. I played many times in the following few days, no more freeze issue occurred.
I also met this kind of bad U2 NAND issue on a CV-1000D board.
It's a long story.
I bid one issue DDP-SDOJ board on Yahoo Auction 2 years ago at a low price. The seller described that the game almost 100% freezes at character selection. There was little chance that the game could be played through.
I did some test after i received it. The game would randomly hang when playing demo. And it would 100% freeze after selecting any of the 3 characters. I reboot the board many times and only 1 time i could play through the game without any issue. I didn't find any graphic glitch in game, either.
I checked the board under microscope, nothing abnormal.
At first, I thought there might be some problem with the DRAM chips on board.
I bought brand new DRAM chips and replaced them all on board, but the issue was still there.
I didn't have a clue where the problem really comes from.
Then I thought if there was any data corruption in the NOR and NAND chips. But there was no SDOJ game rom available on internet at that time.
I temporarily give up repairing this board and kept it in the drawer.
By chance, i got another good CV-1000D board this year. I decided to continue repairing the issue DDP-SDOJ board.
I did a swap test , I moved the 4 SDOJ rom chips to the good CV-1000D board, and the same issue was still there. So I could confirm there was data corruption in any of the 4 chips.
DDP-SDOJ mame rom is now available on internet. I downloaded a copy and tried to burn the data into new NAND/NOR chips with a NAND programmer.
I first burned U2 chip and did a quick test. The game was OK and could be played through without issue.
So moved the rom chips back to the original CV-1000D PCB. Yeah! It's completely back to normal. I played many times in the following few days, no more freeze issue occurred.
