I just bought a new Power Man 350W switching power supply for my old computer. I bought this PSU because it's not as noisy as the old one (actually it's not really nosy at all compared to the old one--that's why I want to replace it) which is also rated 350W (Power Box).

Now, when I plug all the necessary cables into the motherboard and press the power button, the computer is being completely unresponsive (there is not even an attempt by the CPU to start spinning the fan for a split second) though the small green LED on the motherboard is lit up.

As a test, I even unplugged the hard drive along with the CPU fan in the hope that it would lower the overall load on the PSU. The same thing. The computer just won't start.

But when I plug the old one back in, everything is working just fine. The new PSU appeasers to be working fine using the paper clip method. So, it's not broken or anything like that.

So, that's my problem and I don't know what I really should do in this situation. Any help is welcome and highly appreciated.

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    When you buy a generic brand PSU you can't expect 350w out. Check the side panel for each PSU, what does each one say about the 3.3V,5v, and 12v lines in terms of amps? – cybernard Jun 26 '17 at 22:34
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    Notice the 180w vs 220w much less actual power here. The old one has a ton of 5V.the 1A difference on the 12v channel probably doesn't matter. 3.3v isn't all that common, so if I had to make an educated guess your 5V channel is way down 25A vs 40A. – cybernard Jun 26 '17 at 22:53
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    @user69786 replace your PSU with a better PSU, what you purchased, is a generic substandard PSU – Ramhound Jun 26 '17 at 23:18
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    The new one has much lower 3.3V and 5V current capability. Even it's 12V capability is lower. If you were anywhere close to the edge with the old supply, you're likely in trouble. What parts are in your old computer? What CPU, mobo, graphics card, and disks/SSDs does it have? Are you anywhere close to the edge with a 350W supply? – David Schwartz Jun 27 '17 at 0:08
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    it was already stated that OP has unplugged everything auxilliary, and the pc does not boot. Whilst a Pentium-4 CPU or an AMD Athlon would need a lot of energy, anything else newer is moot, as it would not even come close to that much consumption – Hicsy Jun 27 '17 at 0:50

1) Check the mains voltage switch 110-220 v is correctly set

2) recheck that all connectors are full seated

3) there is no paper clip power supply test method

you have a bad 'new' power supply return to vendor ):

  • I think OP was just referring to the fact that the power-supply is turning on, when using the paper-clip method, (which in your case would rule out #1) ... they didnt necessarily mean that paperclip trick was confirmation of a rail successfully working under load – Hicsy Jun 27 '17 at 0:30
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    I still think this is the most likely answer. Check the connectors again... GPU extra power probably not required, but the motherboard probably has a +12v 4/8-pin connector that needs to be checked. Your motherboard might have a power-button on it near the CMOS battery, try using that - or short the power_sw jumper (or even the connector). This eliminates the front-panel not needing power for some non-standard button setup. Otherwise, I think it's safe to say that the PSU is DOA. (Your reseller can likely confirm this in their shop with their test-bench PC) – Hicsy Jun 27 '17 at 0:55
  • Thanks. I returned it to the guy who sold it to me. He check it on his own motherboard. The thing didn't work there either. Therefore, it was a faulty PSU. He replaced it with a new, working 350W one. It had nothing to do with the fact that the PSU didn't have enough wattage to power the computer. So, the problem has been solved. Thank you all for your help. – user563245 Jun 27 '17 at 21:54

the cybernard guys is right the amper of voltage is to way difference here new one have lower power wattage , i think u can unplug Disk Drive and other stuff as much as u can and see problem still there or not maybe only 10 or 20 watt lower connected device to the mainboard or to the power supply can help you turn on the pc but i think if u have a graphic card that need power from you power supply its meaning ur power supply is not enough for your pc anyway higher power supply wattage is better because sometimes graphic cards and even ur cpu will use more than normal so always 50 or 100 more watt is better than that u can't even turn on your pc .

  • This is the graphics card that's installed in the computer: msi.com/Graphics-card/N210-MD1GD3HLP.html#hero-specification – user563245 Jun 26 '17 at 23:35
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    this graphic card didn't use too much power but for testing that u need higher power or not unplug the graphic card from the mainboard and see still u can't turn the pc on or not , maybe you didn't connect all cable to the mainboard ? did u check them all ? – Mojtaba Golestani Jun 26 '17 at 23:46
  • @MojtabaGolestani - Here is a suggestion to avoid future downvotes. Don't provided commentary about another answer. You should also avoid words like "I think", either take the time to "know" or you shouldn't even submit the answer. As to the reason I am even making this comment, when virtually every single one of a user's answers, appears in the low quality queue there is something wrong with their answers. – Ramhound Jun 28 '17 at 4:57
  • u know how to fix the computer hardware problem at first u should try everything to know what cause the problem when the computer is not on my desk i should ask them to do something to know what cause the problem . so i don't say i know ur power is not enough for all your component and devices that are connected to it !!! maybe the power broken ! how should i know that ? ur so funny i wait for the one who asked the question so they can tell me answer is bad or not . but i know something that i wasted my time here because 90% of unanswered questions have 0 way to done ! – Mojtaba Golestani Jun 28 '17 at 5:06

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