Nothing... I cleaned all with dry contact cleaner! I going crazy!

-Reboot always ok

-After power off (with keyboard or power button) mac will not start.

-After power off, power on (mac not start), power off, power on... mac start without problems!

-When mac not start I ear the speaker try to reproduce a chime but stop at first second and I listen a "crank" from the speaker...

-I think is the caps but I have tried to power off, power on (not start), power off..... wait one hour.... mac power on ok! Another test is power off, power on (mac not start), power off... disconnect powercord, power on (caps discharge)... when I power on the mac start correctly! This is exclude the caps?