Recently a 250V ATX computer power supply (of model number HP-Q250GF3) running in one of my frakenstein machines failed. A friend of mine, curious about the operations of these machines, and knowledged far beyond me in electronics has told me that he will attempt to repair it. Does anyone reading this post know where to find the circuit diagram for such a power supply, or one that will suffice, so that he can diagnose the problem. Additionally, any advice from someone who has already repaired a computer power supply would be helpful. Thank you.

 

Google your part number for information

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Have you seen the results that come up when you google the part number? This reply has most definitely not been helpful.

 

When a PC style switcher fails the likley culprit is a capacitor failing short circuit. No telling what else it blew when it went. Look for black marks =) Better yet buy a new power supply, you can get them for 20 bucks. Find a local computer recycling center, you can get cheap or even free power supplies from them.

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Interesting idea?, I would have said that's one of the most unlikely things to happen?.

MUCH more common is the startup resistors going high or O/C, capacitors going high ESR, or transistors going S/C.

But as suggested, easier to jusy buy a new supply - they are also horrible to work on.

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Here are some few ideas.

1.Remove the power unit from the computer.
2.Check the four diodes or (Bridge) & the 400v capacitor (through live wire) is working properly.
3.Then check the smoothing capacitors (200v)near the 4 diodes.be careful when checking high voltage can give a shock.
4.You can see some power transistors (TO220) near the diodes area before going to transformers.check them working properly or not.
5.If this all in a good condition look at the fuse (5A) is broken or not.if broken replace it.

Note: Do not replace the fuse in the begining of repairing.short circuit in the above mentioned parts can burn the fuse even the short circuit in the output section.here I mentioned only few components which is normally burning parts(due to heat).other parts should be take into account by viewing & measuring the results from a multimeter.

These methods done in the primary section of the power supply.If you satisfy with the repairs done in the primary unit can power up the power unit & short circuit the two wires PS ON & GND.

If you see the fan is start runing or check with a multimeter at the cable ends power is coming or not.If it is not must also see at the output switching section very carefully.

Note: Before connecting to the pc verify that the correct voltages are coming from the ends.

these are the basic steps you can do at home.If none of these work take into a experienced member or better buy a new one.

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