Dedoks, before replacing your motherboard, follow what rj713 is suggesting. If you still have no success, you may have to dig deeper. Disassemble your computer right down to the motherboard. Follow this guide. Inspect your motherboard for any signs of burned, charred, or missing components. Take you time with it and look careful. It does have a lot of SMD components and requires a sharp eye ;-) Find the component PF1 which is a 5A fuse and PD5 which is a special diode, called a voltage suppressor, replacement part is number is P4SMAJ20A SURFACE MOUNT TRANSIENT VOLTAGE SUPPRESSOR POWER - Pan Jit International Inc.. Make sure that those are okay. You may need a multimeter to check on those. Hope this helps, good luck.
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motherboard replacement
crwdns2934271:0crwdnd2934271:0 Monte crwdne2934271:0
I would say that it could be the motherboard.
crwdns2934271:0crwdnd2934271:0 Luigi crwdne2934271:0