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(Solved) - +5VSB Power Supply Failure?

(10 posts)
  • Started 3 years ago by jacobt
  • Latest reply from jacobt
  • Topic Viewed 2589 times


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Posted yesterday 
Posts: 5

Hi forum,
First of all, I just want to say thanks to all of the active forum community members for your helpful insight and contributions. I peruse this site from time to time to troubleshoot and find answers to various problems I've had.
My current issue is as follows.
I have a PC which I built from scratch about a three and a half years ago.
All of the sudden, it stopped powering up. When I flip the power switch, the fan in the power supply does not spin.
However, the green LED on the motherboard does light up.
Because of this, I presumed that the problem was the power supply, naturally.
I called Ultra products support to access my warranty information. They told me that my lifetime warranty was expired, as I had never registered the product (That's really neither here nor there, but may be useful information to those of you looking to buy a power supply-or having recently bought a power supply made by Ultra).
They did tell me that the power supply could be fine and it may be just receiving an incorrect signal from the motherboard. This is something I had never heard of before. Further, they told me that testing the PSU with a multi-meter does not provide an accurate test of the PSU either, and that a PSU tester is to be used. I'm not an advanced hardware technician, but I always thought that a multi-meter would read the power supply in the same way that a specifically designed tester would.
So, in any case, I ordered a power supply tester from Hong Kong and tested the power supply. With the 24-pin and 6-pin connector cables connected, it simply reads +5VSB. This, by my understanding is the standby power voltage. The HDD, SATA and other connectors don't register anything.

I'm not even positive if this tester works, as I've got nothing else to test with it for a baseline, right at the moment.
But, it seems like for some reason, the power supply is only outputing a standby level.

Could this be an issue with the power supply or even the wiring in my home?

The support guy from Ultra told me that the power supply needs to receive a signal back from the motherboard in order to output the correct voltage, as per various advanced power management protocols.
I don't really want to get a new power supply if I don't need to, as my budget is pretty tight right now. But, of course, needing to drop a bunch of money into a new motherboard would be worse.

If anyone is able offer their advice or guidance in this situation, it would be strongly encouraged and largely appreciated.

Here are the system specifications:

Asus M3N78 PRO Motherboard - Socket AM2+, Geforce 8300, ATX, HDMI, SATA, Gbit LAN, Hybrid SLI
AMD Phenom 9500 Processor HD9500WCGDBOX - 2.20GHz, 4 x 512KB Cache, 1800MHz (3600 MT/s) FSB, Agena, Quad-Core, Retail, Socket AM2+, Processor with Fan
OCZ SLI-Ready Dual Channel 4096MB PC6400 DDR2 800MHz Memory (2x2048MB)
Sparkle SFPX94GT1024U2 GeForce 9400 GT Video Card - 1GB DDR2, DVI, VGA, PCI-Express 2.0
Ultra LS500 Lifetime Series 500W Power Supply - ATX, SATA-Ready, PCI-Express, Lifetime Warranty
WD Caviar 500GB Serial ATA HD 7200/8MB/SATA-3G (x2)

Thanks again. I look forward to members' input on this matter.

Posted 3 years ago
Posts: 13598

Use this trick, and test again,

Posted 3 years ago
Posts: 6298

Borrow a power supply that works and see if that fixes it.

Posted 3 years ago
Posts: 5

Thank you very much for your responses, Lighthouse and Xhi.
I was able to find another PSU in a box of a stuff in the basement. I believe it is in new condition and working, however it is only 450W versus the one that I have been using being 550W.
I connected it direct to the tester and power it up, it beeps, the fan comes on and the indicator LED lights light up: +12V, +3.3V, etc. However, when I connect it to the computer using the 24 pin and 4 pin connectors and power it on, it is the same thing as previous. The indicator LED on the motherboard comes on, but it does not beep and the fan does not come on, nor do any fans connected to the motherboard.
This is bewildering to me.
Is the power supply just underpowered for the board, or is something wrong with the motherboard?

Thanks in advance.

Posted 3 years ago
Posts: 5

Here's what the manual says about power supply. Though, I would think the power supply's fan should come on when plugged in, regardless. Right?

• For a fully configured system, we recommend that you use a power supply
unit (PSU) that complies with ATX 12 V Specification 2.0 (or later version)
and provides a minimum power of 600 W.
• Do not forget to connect the 4-pin ATX +12 V power plug; otherwise, the
system will not boot.
• Use of a PSU with a higher power output is recommended when
configuring a system with more power-consuming devices. The system
may become unstable or may not boot up if the power is inadequate.
• If you are uncertain about the minimum power supply requirement for your
system, refer to the Recommended Power Supply Wattage Calculator
aspx?SLanguage=en-us for details.
• The ATX 12 V Specification 2.0-compliant (500W) PSU has been tested
to support the motherboard power requirements with the following

Memory 1024 MB DDR2-800 (x4)
Graphics card: PCI Express x16 NVIDIA 7900GTX
Serial ATA device: SATA hard disk drive (x2)
Optical drives: DVD-RW

Posted 3 years ago
Posts: 6298

To me if two power supplies give the same results then I would suspect the motherboard or one of the attachments not working properly. Your test seems to indicate it is NOT the power supply as much as you might like to will it to be. The difference between 450 and 550 at startup is negligible.

Posted 3 years ago
Posts: 14920

There is a row of Capacitors on the mother board.

My bet is that if you inspect them, you will find one or more that has "popped".

Posted 3 years ago
Posts: 5310

Couple of other things to look for beside the leaking caps.
Unplug your Cd burner, using a multimeter press the power on button and check the voltage on the power connector. You should be getting +12vdc between the red and black wires.
You should also have a couple spare molex connectors you can check the voltage on instead of the one for your burner.
The other thing to try is unplug your HDD, remove your video card if you have an external one, unplug your Cd/DVD burner and your wireless adapter again if you have an external.
This will allow you to check just your PSU, Mobo, and power switch.
If still nothing I would jump the power switch. If still nothing then suspect the mobo. If you don't have the proper tools or know-how then yo umight want to take your system to a good computer repair shop for diagnostics.

Posted 3 years ago
Posts: 902

Also check the power switch button. Might be broken and does not contact when pushed. Try shorting the power switch pins (2 pins) on the mobo with a small screwdriver (or any small piece of metal) and see if it powers ON.

@germ-x, I think it's the yellow and black wires on the +12vdc.

Posted 3 years ago
Posts: 5

Thanks everyone for valued input. It turns out that the 550W power supply was bad, and there was a short in the power switch.
Also, I found a capacitor under the motherboard which had fallen or broken off of something. I'm not sure what it goes to, but it's working fine.
Thanks again, everyone.

Accepted Answer · Posted 3 years ago

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