Anonymous
Anonymous asked in Computers & InternetHardwareDesktops · 8 years ago

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 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?

4 Answers

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  • Anonymous
    8 years ago
    Favorite Answer

    If you think that the power supply CAN be repaired, then you've already failed your class. Not trying to give you a hard time at all. But literally every component in that puppy needs to be replaced. You going to spend the next week or two (and a hundred bucks) disassembling the thing to replace EVERY component???

    You need to find a DIFFERENT broken power supply...one that failed on its own...as opposed to being destroyed by operator error. THEN if you are lucky the repair might come down to replacing a capacitor or two.

    In general though, it's never a good idea to try to repair a computer power supply. For the average person, it can be a DEADLY mistake. For an electronics tech, it can be a waste of money and effort (easier and cheaper just to replace it).

    Again, if this is your class assignment...you need to throw away your old design non-PFC dinosaur and find some other power supply to try to repair.

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  • Anonymous
    8 years ago

    First... the first three three responders need to be slapped!

    The only reason to be so rude and negative is to make oneself feel important at someone else's expense.

    Yes, you made some mistakes and you already know that.

    So... when you get sparks and heat it means something is shorted. In other words, you've got two or more pieces of metal touching each other that shouldn't be touching. Perhaps some solder got into places it shouldn't be or maybe the original power surge melted insulation and allowed the touching. If you're certain you only see sparks around the capacitor you just replaced, my first guess would be solder overlap or perhaps you put the capacitor leads in the wrong holes.

    As responder 4 suggested, look for burned or melted insulation (varnish in coils, rubber/plastic on wires) and look for wires, solder or other bits and pieces that shouldn't be touching.

    Also, make certain that you put the new capacitor wires in their proper places. Things like capacitors, transistors, diodes, etc. have polarities (sort of like a front and back) and have to be oriented properly. Look for the positive lead mark (or study the old one and match the new one to it) and make sure it goes in the positive position, meaning the same hole the old one was in. As for the person that said power supplies are deadly...that's only true if they're plugged in or...and this is VERY IMPORTANT!... if there's a capacitor that is still holding a charge big enough to hurt you. Capacitors are electrical storage devices and will, like a battery, hold a charge for a long time (even when the power is turned off) unless they are discharged. Don't get your body parts in the way of that discharge.

    Now, as responder 4 said, get your magnifying glass and study those parts and connections.

    Source(s): Trained in electronics repair.
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  • Anonymous
    8 years ago

    When you carelessly put double the voltage across something like that it immediately blows the weakest parts. Think about it, a pair of 200v capacitors which are actually on the protected side of the supply (they can't be connected to the 240v side or they would instantly blow) it would indicate something else had broken down and passed mains onto the DC side. That is what happens when you do not check properly. There are inductors, diodes and other ICs which are more likely to fail first. You obviously do not understand electronics or diagnostics, that is what went wrong.

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  • 8 years ago

    Never, unless you have money to burn and don't mind getting electrocuted, attempt to repair a PC power supply. They are notoriously proprietary and not easily repaired. They also tend to be guaranteed for a long time, usually longer than you'll need them before the PC wears out.

    None of that helps your problem. Call the manufacturer and get a tech support person on the phone. Tell them your fix and see if you can find some nice soul who will walk you through the repair or possible troubleshooting. If the PSU is old enough, he/she may even be in a position to send you some refurbished parts on the cheap (or free) for you to try and complete your project and get the grade you deserve. (I'd give it to you just for trying.)

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