No power after external power failure

I have an eMachines H2824 tower that went out of warranty 2 months ago (conicidence??). Yesterday, possibly due to a severe power outage (the power came and went 3 times, with loud bans coming from a piece of equipment in the street outside, before staying off for several hours), the tower went dead. That is to say that it will no longer turn on at all. I checked in Troubleshooting in the accompanying booklet and it suggested that after an external power failure it is necessary to unplug the machine from the wall, wait 10 secs, and replug before pushing power button. This did not work either. Anyone able to suggest the variety of technical problems that may be involved here, and especially any bright ideas for attempting to restart the machine without having to take it to a techy? Thanks...

The first thing I have to advise you is to change the Power supply unit. Before buying one change it with another one (probably from a friend's PC) and see if it is working. To remove the power supply unit, you need to remove your tower's case, and unscrew the power supply and remove it. the power supply is the metallic box on top of the computer at the back.