This is my first post here I bet PS2 modding is not really interesting anymore but I can still hope for an answer that will make my day) Anyway, I tried to put a Sumo Lite modchip but after hours of work ( that was really painful) my PS2 still work despite a few accidents that i managed to correct. But unfortunately the chip does not have any effect at all. So, backups still cannot be read I have by the way an european SCPH-77004 with a GH-052-02 motherboard (I think it's a V15). I couldn't really find any schematics for that kind of chip. So, i used like some forums said a ModBo4 and a Matrix infinity diagrams. I attached the pictures of the mod chip to let know what it looks like.
I could find a place for all connections except for the numbers ones (1,2,3,4). I guess they would be for some fix like for V12. I assumed also that VCC was 3V and RT reset. And I didn't use the ones under the modchip because they are the same as the one on top. I connected also the 2 GNDs because with just one the DVD's lens part wouldn't go backward anymore. I check every connections with a multimeter and everything seemed correctely connected and without shortcut. But i noticed that the resistance measured between VCC and GND is really low, close to shortcut... I think that's pretty much all i can tell. Thank you for reading this and hopefully you'll find a solution to my problem. Thank you