I modded my ps2 with a Magic V (23 wire version). My ps2 is a version 5 or 6. I soldered all the pins to the motherboard using some very thin wire (that I used to mod xboxes). I only had trouble with one of the pins where I shorted two of the surface mount pins on one of the chips, which I painstakingly cleaned up (they aren't shorted anymore). So I solder all the wires to the motherboard and to the modchip and make sure they all are soldered properly with a multimeter (I checked the resistance on the highest setting possible). All of those checked out alright. So I insert a game backup (Sony DVD-RW) and it didn't work (yes the game does work on other modded ps2s). I try an other game and it boots perfectly.
So just to make sure, I reset the ps2... the game doesn't boot anymore, it just kinda does its thing at the browser screen. But when I turn off the modchip, it immediatly says that its not a ps2 game, and it can still play retail games when I turn off the modchip, but not always when its on.
Ok, I resolder all the wires and add some thicker wires for the round and 3.3v rail. No go. I give up for a couple weeks and don't touch it. Then I try an other game backup on a Philips DVD+RW. It boots just fine. I reset the ps2, and it doesn't boot anymore... I cycle the power and boot again. It boots... so I try the game to see if its a good burn. The burn is fine and the ps2 can load while I'm driving really fast on a highway (no speed blurs either).
I reset the console again and it doesnt work... WHAT GIVES?!
EDIT: all backups were burned at 1X speeds