Computer Power Supply Capacitor Replacement fail?

i have a very big problem right now.. i had a broken power supply i remember it blowing up years ago when i plugged it in on a 220v when the power supply's built in toggle switch was turned on to 110 volts.. i opened it up and saw the two huge 470 microfarrads at 200v.. i set it aside for a while, i was... show more i have a very big problem right now..

i had a broken power supply i remember it blowing up years ago when i plugged it in on a 220v when the power supply's built in toggle switch was turned on to 110 volts.. i opened it up and saw the two huge 470 microfarrads at 200v.. i set it aside for a while, i was just a student and these capacitors were a bit costly for a student like me..

this year, i had the oppurtunity to replace it. our instructor told us to bring a broken power supply and had the diagnostics at out class.. so our group had an edge, i already knew what it was because of the previous power failure.. now for our test, we were ask to bring this tuesday in working condition.. since we're a group working on a power supply, we have to contribute for the capacitors, since i have the broken power supply assignment, we all agreed it was fair.. our instructor didn't really taught us how to solder and patch things up. he assumed we already knew it from our past subjects before, he's new to our school that's why he didn't know that we're still taking the basic electric circuits, electronics subjects along with his class.. that's really how it goes to our school.. but that wasn't really a problem for me, i know how to solder somehow, aware of the polarity, i used to build led lamps before, etched my own board.. so i think, soldering wouldn't be problem for me, just replacing capacitors..

so there, we bought the capacitors, i soldered it in place, but when i plug it in.. it sparked and it smelled like roasted corn.. i instinctively unplugged it and indulged myself in sorrow.. where did i went wrong??? im beginning to doubt my skills and knowledge, i used to be good at this? what went wrong? the capacitor doesn't look like broken, it's not bulging, not even burned lead terminals? what would i tell my groupmates? and the money, its a wasted money.. on top of that this is our prelim exam, if i don't fixed it we will all get 0% on practical exam.. i don't really know what went wrong.. please help me.. could it be that it's not only a broken capacitor?? did i damaged other parts after the current failure? i don't see any sparks flying off other than the place where the capacitors were soldered.. please tell me what could be wrong?
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