Replacing broken power supply

Hello all,
Im spanish so sorry for my english

I've an old PC that became to work very bad and suddenly stopped working at all. I found that its power supply was broken. It's an ATX 2.03 250W.
i tried to install an other power supply that I have (atx 2.03 p4) with same amperage and voltage but it says 400W. I thought it should work ok but when I turned on the pc it started to smell like burnt. As far as I know there wont be any problem using this power supply insted of the old one :S maybe mobo is broken so it broke my old power supply and thats why this other supply smells like burning?

Please help me found if it should work ok with this other supply or if its normal that it smells like that because it has higher W. Or because one is atx 2.03 an the other atx 2.03 p4.

Thank you in axvance!!

Hi Wr25fgff.

Your new PSU should have worked just fine for your PC, and NO it should not smell burnt, that is bad. If there was a switch on the back of the PSU for 115v and 230v, was it set to the right one for where you live? There could be something causing a short in your PC and that could be a bad motherboard or CPU but it is really hard to know if that is the problem.

If there is anyway you can barrow a friends pc to test your motherboard and CPU on and make sure that is the problem, it could save you some money, instead of just buying parts that you are not positive they are broken yet. Or another choice, if there is a electronics shop that can test your parts for you that would work. Otherwise theres no gaurantee you are replacing the part that is defective or not.

Was the MOBO and or the Power supply from an old DELL pre-built system ?? -- several years back DELL would have the MOBO and Power supplies they used manufactured to their specifications and they had a different wiring than the standard ATX specification (so you had to use DELL powersupplies with DELL MOBOs and had to buy them from DELL) -- If this is the case then plugging in a standard ATX Power supply could burn out the PSU or MOBO since the wiring is different. (so be careful if testing that MOBO or PSU if they were originally from a DELL !!)

Thank you both for your answers
I found the manual of my old mother board:
GA-7IXE4 AMD 750 AGPset REV 1.0 Third Edition

I searched for info about the ATX Power Port and saw this table:
PIN(3,5,7,13,15-17) -> GND
PIN(1,2,11) -> 3.3V
PIN(4,6,19,20) -> VCC
PIN(10) -> +12V
PIN(12) -> -12V
PIN(18) -> -5V
PIN(8) -> Power Good
PIN(9) -> 5V SB stand by +5V
PIN(14) -> PS-ON(Soft on/off)

I compared it with the one from where I got the other power supply and are identical, so I guess both ATX Ports are the same, and that shouldn't produce any "problem" ...

I'm now almost 100% sure that the problem is with my mother board, or maybe any other component :S ... can you help me find out which one is ? Any way of "testing" the mother board ? Or maybe you saw a case like this and remember how to solve it ?

Thanks x10000

It started to freeze randomly ... I was browsing the net looking for possible reasons and the most I found were power supply or faulty mother board.
I've 3 memory sticks and I played with all of them alternating to see if was any of them but with every combination it ended freezing.
So I eliminated memory as a possible problem, and thought about mother board or power supply. I now know that it's very possible that the power supply wasn't so I bet for mother board... anyway you think about the CPU too,... can I do anything to check it ? (I don't have any other PC with that socket for CPU)

if you get some thing like this:
http://www.newegg.com/Product/Prod [...] -_-Product
you can test your power supplies and see if they are fried