Sign in with
Sign up | Sign in
Your question

Faulty psu? bad power switch?

Last response: in Components
Share
December 27, 2009 2:20:09 AM

okay so i have a problem with my computer.
heres the story... last monday i came home from school, (left the pc on) and i went to go finish dragonage, but i had a leak in my WC setup (2 days after i did a 24hr leak test...) so i turned my system off, and cleaned 95% of the liquid, there is some liquid in the holes on the PCI slots, pain to get out.... so after i cleaned it i tryed to turn the system on, no power. (few days go by) its thursday, try to get my pc to turrn on, check all the connections, all are OK. nothing, then on friday i turned it on and well, it turned on, installed win 7 and thought i was good, nope, today i try to turn it on and nothing happens,

heres what i have tried to do:
- use my old working psu from my backup pc (the one im using now) and install it in the other one, nothing..
-jumped the psu and it works, everything lights up etc,
-tried using the old psu again, and from my memory the motherboard turned on cause the bottom of the mobo there is a little display that shows 2 numbers/lettrs and it lit up.
tryed using the power switch cable from my old case, nothing...
-tryed putting the reset switch into the power switch header, nothing.

so i am not sure if its the motherboard header or the case switch. the psu seems fine cause it works when i jump it and NO liquid got into it.

i need some help cause well it sucks not being able to use my 5850 crossfire setup.

thanks in advance

-also i didnt know what section to put this under so i put it here, hope thats not a prob,

specs:
case: antec 1200
mobo: asrock x58 extreme
cpu: core i7 920
ram: 6gb OCZ
HDD: 2 640gb in raid 0, 1 TB HDD
gpu: 2 5850's
a c 144 ) Power supply
December 27, 2009 10:39:24 AM

wahjahka said:

so i am not sure if its the motherboard header or the case switch. the psu seems fine cause it works when i jump it and NO liquid got into it.

There are two problems with using a jumper to see if the PSU does start. First, there's no load on the PSU. Second, that does not check the PowerOK signal on the gray wire. This signal needs to be present before the system will boot.

Try to verify (as well as you can) that the PSU works. If you have a multimeter, you can do a rough checkout of a PSU using the "paper clip trick". You plug the bare PSU into the wall. Momentarily insert a paper clip into the green wire pin and one of the black wire pins beside it. That's how the case power switch works. It applies a ground to the green wire. Turn on the PSU and the fan should spin up. If it doesn't, the PSU is dead.

If you have a multimeter, you can check all the outputs. Yellow wires should be 12 volts, red 5 volts, orange 3.3 volts, blue wire -12 volts, purple wire is the 5 volt standby and should always be present. The tolerances should be +/- 5%. If not, the PSU is bad.

The gray wire is really important. It sends a control signal called something like "PowerOK" from the PSU to the motherboard. It should go from 0 volts to about 5 volts within a half second of pressing the case power switch. If you do not have this signal, your computer will not boot.

Unfortunately (yes, there's a "gotcha"), passing all the above does not mean that the PSU is good. It's not being tested under any kind of load. But if the fan doesn't turn on, the PSU is dead.

On to the real troubleshooting ...

Disconnect everything from the motherboard except the CPU and HSF, the two power cables going to the motherboard,and case power switch. Boot. You should hear a series of long single beeps indicating missing memory. Silence here indicates, in probable order, a bad PSU, motherboard, or CPU - or a bad installation where something is shorting and shutting down the PSU.

To eliminate the possiblility of a bad installation where something is shorting and shutting down the PSU, you will need to pull the motherboard out of the case and reassemble the components on an insulated surface. This is called "breadboarding" - from the 1920's homebrew radio days. I always breadboard a new or recycled build. It lets me test components before I go through the trouble of installing them in a case.

It will look something like this:
http://www.tomshardware.co.uk/forum/page-262730_13_0.ht...
You can turn on the PC by shorting the two pins that the case power switch goes on.

If you get the long beeps, add a stick of RAM. Boot. The beep pattern should change to one long and two or three short beeps. Silence indicates that the RAM is shorting out the PSU (very rare). Long single beeps indicates that the BIOS does not recognize the presence of the RAM.

If you get the one long and two or three short beeps, test the rest of the RAM. If good, install the video card and any needed power cables and plug in the monitor. If the video card is good, the system should successfully POST (one short beep, usually) and you will see the boot screen and messages.

Note - an inadequate PSU will cause a failure here or any step later.
Note - you do not need drives or a keyboard to successfully POST (generally a single short beep).

If you successfully POST, start plugging in the rest of the components, one at a time.
m
0
l
!