recently when I opened the case, I drop off a screw driver right on the motherboard, and suddenly the computer turning off. I found out that the powersupply did not work, so I bought a brand new power supply and turned on the PC right away. But after 5 minutes running, suddenly the fuse in the power supply blew up. The computer technician said that there were a short circuit in my motherboard, that made the powersupply blew up. So they suggest me to replace with a new motherboard Question : could any one tell me how a short circuit in motherboard, where there are only small DC current can make a fuse in power supply, that is supposed to be a protection for AC current from electricity supply.

Hi, When motherboard has short curcuit it can cause very big DC current through it. But on an other hand power supply has a protection curcuit which must turn off DC power when short curcuit occurs. If you have fuse blown up I think it can be result of your motherboard misfunction, but in means also your power supply unit is not working properly, because its protection curcuit isn't functioning. The only rare case I can think of is your motherboard has such sort of short circuit that its current is slightly above maximum value for power supply unit. As a result protection curcuit not trigger yet, but unit was overheated after few minutes of working and burned the fuse. (Unfortunately the burned fuse means your power supply unit is burned out in most cases.) So it's can be the technician is right and you need to replace your motherboard, but beforehand show it to some experienced technician, wich will be able to measure the motherboard current and make correct diagnose. Good luck, Igor M