Thanks Guys, under a strong magnifying lens and after unsoldering all of them I saw how the pads connect with the circuit. There was still that line left that lead into the pad. After scratching off a bit of the protective layer I was able to connect the negative side of the capacitor to it. Replaced all 4 caps that are below the power connector and after the 3rd attempt turning on the Mac, it actually booted up. So it does start now but it takes a few attempts. It’s a bit funny, even when it boots it comes up with the checkerboard first. Then it disappears and it boots.
Hi Guys, I finally got lucky and scored a Macintosh Classic in good shape. It got (of course) the checkerboard issue due to capacitor leakage. The board looks pretty clean but looking closer revealed that the capacitors close to the power connector leaked (C5, C6, C8, C9) . The one worst was C6 and when I tried to unsolder him I managed to rip off the negative solder pad (the side with the black stripe on the cap). Anyone able to tell me where I can wire the negative of the replacement capacitor to instead? Just hope I am not completely screwed now :-(.