Computer starts up, then shuts down immediately.

Just got a new power supply, plugged everything in, double checked, go to power up, fans start spinning then everything shuts down.

This is the second time this has happened to me ( happened the last time i got a new power supply ) but i dont remember exactly how i fixed it ( if i did anything, i have a feeling it just started working )

Anyways things i have tried

- using the old power supply that worked perfectly fine before
- taking out the battery
- trying 4 different sticks of ram, one at a time, in the four different spots.
- only plugging in the atx and 24 pin
- reseating the cpu ( and applying a new thing of thermal paste since i had some )

still it just starts up for a second then shuts back down.

spec -

case -NZXT M59 - 001BK Black Steel ATX Mid Tower Computer Case
cpu - AMD Phenom II X4 965 Black Edition Deneb 3.4GHz Socket AM3 125W Quad-Core Processor HDZ965FBGMBOX
processor -ASUS M4A785-M AM3/AM2+/AM2 AMD 785G HDMI Micro ATX AMD Motherboard
ram - 6gb ram
graphics - SAPPHIRE 100312-3SR Radeon HD 6950 Dirt3 Edition 2GB 256-bit GDDR5 PCI Express 2.1 x16 HDCP
psu -
Antec High Current Gamer Series HCG-620 620W ATX12V v2.3 / EPS12V v2.91 SLI Ready CrossFire Ready 80 PLUS BRONZE Certified
3 answers Last reply
More about computer starts shuts immediately
  1. I'm by far not an expert but it sounds like a short somewhere. I had that same issue years ago and it was a wire that was grounding out the MOBO. Maybe the PS has a grounding issue?
  2. smede2

    did you find out how to fix it?, i have the same problem/PSU as you
  3. Three main issues cause this to happen and initial diagnostics is fairly simple so start with the least costly component and easiest to replace first.

    Power Switch.
    Turn off the PSU at the PSU switch. Fashion or purchase a working momentary switch with positive and negative leads. The motherboard header for the front I/O panel is a 100-pitch header and will accept 100-pitch connectors. A switch can be purchased on Ebay for about 1USD plus shipping with leads and a 100-pitch dual position single row connector. Identify the - & + pins on the motherboard header for the power switch. Unplug the existing connector, or leads from those header pins and connect the working switch - & + to the corresponding pins. Turn on the PSU at the rear switch then push the new momentary switch. If the computer starts normally, you’re good to go by simply replacing the power switch. If this doesn’t resolve the issue look to the following components.

    Hint: During custom builds I use Molex C-Grid dual row 20 position connectors (depending on the motherboard make) with the required female pins for the power on, reset, HDD LED, power on LED and case speaker leads. It’s more convenient to connect and disconnect, and it looks more tidy then a bunch of connectors.

    Power Supply Unit
    Turn off the PSU at the PSU switch. Unplug the 12volt (if it exists), all PCIe connectors and the ATX connector from the motherboard. Jump the green and any black pin in the ATX connector using a minimum 22AWG sheathed wire with stripped ends or fashion a jumper using corresponding ATX connector male pins crimped to the wire. Turn the PSU on at the rear PSU switch. If the PSU starts and runs for any length off time beyond a few seconds it’s a good PSU. If the PSU does not start, or starts then immediately shuts down, replace the PSU. I’ve read on several forums and have been told by technicians that a possible PSU fire can start using this method, however, I’ve jumped many PSUs this way and have yet to have one catch fire, but be careful anyway.

    If neither of the above two diagnostics resolved the issue, look to the motherboard. Bad capacitors cause a multitude of problems, including faulty voltage readings from the PSU. Examine all caps for crowned tops. If any caps have crowned tops and/or there is residue near or on the capacitor or on the board, the cap is blow. Replacement is difficult if you haven’t a clue how to replace a cap, lack the necessary tools or where to even find the proper capacitors. There are some technicians who do this sort of work, and those who perform this specialty work for corporations require a minimum of 10 like kind motherboards at a time. The cost is about 65USD per board, plus shipping, both ways and with ten boards its quite expensive for an individual, not to mention few of us have 10 of the same boards on hand. There is a firm in the USA that performs cap replacement on single boards and the cost is posted on the site. The site is The owner will answer your online request for a quote in a few days and you can make arrangements through the site for shipping, get packing instructions and gain general information about the firm. It takes awhile so be patient. If you decide to not have bad caps replaced, or not replace them yourself, your only option is to replace the motherboard.

    Good luck
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