Question about Biostar : NF4ST-A9 Socket939/nForce4/DDR400/SATA/ATX Motherboard (MOTBI15)

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No power up when pressing switch

PSU and case switch proven good with back-up mobo. Pressing case switch functioned only intermitantly until yesterday. VSB is 4.56VDC, PS_on reads 0.748VDC and does not go up when switch is disconnected. Shorting PS_on to ground turns fans on but does not post the CPU. Reset has no effect. I am wondering what could be wrong since I am leaning towards Motherboard due to a different issue where the onboard nic would drop connection all the time. Motherboard is less than a year old with no overclocking.

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Re: No power up when pressing switch - Biostar : NF4ST-A9 Socket939/nForce4/DDR400/SATA/ATX Motherboard (MOTBI15)...

Power suplly problem

Posted on Sep 12, 2007

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Pc not booting, no fans spinning, nothing lights up. HALP


Dec 06, 2013 | Motherboards

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Mobo boots up when powering PSU without pressing power button on case.

What do you mean apparently?
"Apparently, no swollen or leaking caps."

Helping someone remotely?

The top round flat seal on the Radial Aluminum Electrolytic Capacitor is called the Vent Cover.

The bottom round flat synthetic rubber seal is called the Bung.
Sometimes just one edge of the Bung pushes down, and out of the capacitor's case; and this allows Electrolytic Paste to be pushed out.

The capacitor may only be on a slight lean, and a lot of capacitors wind up being that way when installed.

You/they need to L@@K CLOSE.

This really means motherboard in hand.
Not peering at it installed in a computer case, with hardware components, or cables in the way.

The capacitor case could just be slightly swelled up.
Hard to discern sometimes. I use a bright light, and have been known to use a magnifying glass, lol!

I realize it is just an assumption on your part, and now mine; as to if there are bad 'caps'.
But I do go along with your hypothesis.

Obviously (IMHO) the motherboard is at fault.

To post back post in a Comment.


Feb 04, 2013 | Intel D865GVHZ Motherboard

2 Answers

I seem to have a problem with the power to my computer. After 2 days of searching all kinds of forums I still haven't found a solution. The computer won't power up, no fans are spinning, not a...

First remove the power plug from the smps and press the power switch few time and wait for few minutes the re plug the power connector to the smps and switch on the computer if you still dont have power then you will have to check whether the smps work to test that its not enough to test the voltage in the 21/24 pin you will have to short the green wire and the black wire and see whether the smps fan is working if the fan is not working then the problem is with smps

Jul 30, 2011 | ASUS Motherboards

1 Answer

Motherboard booting problems...How do I solve?


Try to boot with 1 stick of ram then swap it with the other and try again. Next unplug the case front connections from the mobo header (pins). Draw a sketch where they all go so you don't forget. I'm talking about the power switch, reset SW, HDD LED etc. Also remove anything connected to the back panel printers etc. Also remove the mouse and keyboard. Carefully, momentarily short the pins that were connected to the power switch and note results.

If it still doesn't boot, remove all parts from the mobo except 1 Stick of RAM, graphics card, PSU, and of course CPU. Leave the mouse and keyboard unplugged. Try to boot by shorting the mobo pins again. If it doesn't boot it is most likely either the PSU or the mobo. It could also be the CPU or RAM but it is less likely.

Please get back to us if you have further query else please accept the suggestion.
Thank you for contacting

Jul 04, 2011 | EliteGroup RS482-M754 Motherboard

1 Answer

Nothing happens when I press the power button (good PSU)

You've tested the PSU for volts, although you didn't mention the +12v, the critical thing with all PSU's though is Amps, if there is insufficient amps the CPU will not initiate properly, modern CPU's mobo north and south bridge chips Graphics chips etc are power hungry, volts are one thing amps are everything. Try and borrow a friends PSU to test, then buy a good one if it works with at least 14 amps on the +12v rail, the higher the better.

Jul 05, 2009 | Intel D915GAG Socket 775 Motherboard -...

1 Answer

Tyan S5396 and Thermaltake 1500W

tyan i5400xt.. to test for ground.. pull the board from the chassis and test with a different known good power supply

if the boot works... then you have a power supply issue...

does the board have a post code lighted signal ???

if so.. a bad power supply should goto FF error code

verify you have enough power on the cpu rail with your power supply specifications also

be sure you have all cables 4 pin 8 pin and 20/24 pin connections done correctly.. lastestly check if the board is touching the chassis edge anywhere... could cause a ground

also take and loosen all the MB screws from the chassis.. just let it hang there this will test the grounds needs the screw connections

tyan specialist

Oct 31, 2008 | Tyan S5396A2NRF Dual LGA771 XEON5000 5100...

1 Answer

Motherboard shorted

Unless you have about a $3000 soldering machine and lots of skills soldering, i would say just get a new mobo. the cost to fix it would be lots more than its worth

Oct 11, 2008 | Motherboards

1 Answer

Wont post.

Try a few things for me OK? From what you typed, turned on the psu "the toggle switch on the psu", pc seemed to be starting up. I need you to keep the toggle switch on the power supply in the on position. Press and hold the start button on the PC case to shut it down. Give it a few seconds & power up by pressing the power switch on the case. Notice a differance? Next, unplug everything connected to the pc expect the monitor, mouse & keyboard. Try to boot. Still no? Remove the side of the case exposing the board. Turn the psu off by flipping the toggle switch on the psu, wait till the green light on the board goes out. Grab the Mb ( I know it's tight in there) and see if you can move the board in any direction. Not loose? Re-check all data & power connections for a solid connect. Re-check your case to Mb connections. Also check the PSU, there is a red slide switch it should be set to 115v. Post your findings..

Jan 28, 2008 | ASUS P5ND2-SLI Deluxe Motherboard

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