installed new PSU in my computer it won't turn on :(

[sony mavica]

so my old psu was bad so i got a new on stalled it correctly then when i plugged it in the green light on the motherboard comes on i press the power button but nothing happens so i have unplugged it and checked all the cables and they all are connected fine so what could be the problem

[DimitriP]

If it's not a bad connection of the  motherboard power connector and you didn't knock loose the power switch wire from the header on the motherboard,
any chance the old power supply is not "bad" but it's the motherboard that won't turn on?
It's not an ASUS is it ?


 

[sony mavica]

If it's not a bad connection of the  motherboard power connector and you didn't knock loose the power switch wire from the header on the motherboard,
any chance the old power supply is not "bad" but it's the motherboard that won't turn on?
It's not an ASUS is it ?

yes it an ASUS  i posted about my computer problem on lots of websites forums and people where say it was the power supply problem and i never took or knocked any power switch wires and i have checked them again to see if any where loose

[Halcyon]

Check all the cards and RAM haven't been dislodged (i.e.: Re-seat everything). While you're at it, give it clean and blow/vacuum (very gently) any dust and crap.

[sony mavica]

Check all the cards and RAM haven't been dislodged (i.e.: Re-seat everything). While you're at it, give it clean and blow/vacuum (very gently) any dust and crap.

ok i will have a look now

[Roeland_R]

Check the battery on the motherboard. I have seen bad ones preventing boot.

[sony mavica]

Check the battery on the motherboard. I have seen bad ones preventing boot.

thanks but i did replace that about half a year ago but it was a cheap one it could be bad i will replace it now

[sony mavica]

replaced it but computer still will not turn on

[rs20]

Thou shalt test voltages!

Completely unplug the PSU from everything else (except for the mains plug, of course) and check that +5VSB is providing 5 volts. The SB means "Standby", so the PSU should be providing 5V there, even if the machine is off.

Then, using a little bit of wire, short the green wire (PS_ON#)on the main 20/24-pin plug to one of the neighboring black wires. This should turn the power supply on (fan spinning, etc), and will bring all the other voltages up. Check the 3.3V, 5V (non-standby), 12V, and -12V. It's not a problem if they're not super-close to their nominal values, as the PSU is optimized for being under considerable load.

If these tests all work as expected, then it's entirely possible that your motherboard is at fault. It's impossible for people on the internet to blame something on the PSU with 100% confidence, if the little transistor on the motherboard that tells the PSU to turn on is blown, then the problem looks exactly like a PSU problem but the problem would physically lie on the motherboard in that case. The only sure way to debug things like this is to swap in known-good components until the problem goes away (or even, swap components around and see which components carries the fault around).

[sony mavica]

I'd like to hear that another PC won't power on with the power supply. It may not be the PS after all. I'd disconnect everything that isn't needed to get a Bios screen, including more than the minimum RAM.

If the PS is dirty, along with the rest of the PC then get a brush and clean it out. I use an old paint brush. It might be heat related. Why do you think it is the PS?
I just replaced a PS on my PC. I had a "new" one but The old one worked except the PC rebooted occasionally under heavy load. At this stage I don't know it was the PS. If it hasn't rebooted in a month I'll be pretty confident but it may just have needed a clean from accumulated dust.

i gave the computer a good clean already

[Halcyon]

Do the fans spin up when you power on? Do you get any error beeps?

[sony mavica]

Do the fans spin up when you power on? Do you get any error beeps?

nothing at all happens only the green light on the motherboard comes on

[Brumby]

Nothing happens at all? - not even with the fan on the PSU??

I'm inclined to try this before doing anything else...

Thou shalt test voltages!

Completely unplug the PSU from everything else (except for the mains plug, of course) and check that +5VSB is providing 5 volts. The SB means "Standby", so the PSU should be providing 5V there, even if the machine is off.

Then, using a little bit of wire, short the green wire (PS_ON#)on the main 20/24-pin plug to one of the neighboring black wires. This should turn the power supply on (fan spinning, etc), and will bring all the other voltages up. Check the 3.3V, 5V (non-standby), 12V, and -12V. It's not a problem if they're not super-close to their nominal values, as the PSU is optimized for being under considerable load.

If the PSU springs into life, then there is going to be something wrong with the 'power on' circuit from the front panel.  Could be a broken switch, a lose connection or anything else that interrupts the 'power on' signal.

[Halcyon]

If you short out ATX 24-pin connector's green wire to ground, the PSU should turn on. You should see 12V, 5V and 3.3V.
You don't need a mobo to test the PSU.
If it turns on, then your mobo or front panel connection is busted. If not, your PSU is busted.

That! Do as this man says.

[Red Squirrel]

If you can confirm power comes out of the PSU as suggested, next step is to check the power switch motherboard connectors.  Those can be tricky as you're usually trying to install them in a tight/odd angle with everything else already being installed.  I would also not rule out the actual power button on the case.  If you unplug the plug just short out the pwr button pins on the motherboard to see if it turns on.   That will rule out the case power button.
 

[sony mavica]

If you can confirm power comes out of the PSU as suggested, next step is to check the power switch motherboard connectors.  Those can be tricky as you're usually trying to install them in a tight/odd angle with everything else already being installed.  I would also not rule out the actual power button on the case.  If you unplug the plug just short out the pwr button pins on the motherboard to see if it turns on.   That will rule out the case power button.

the power button works

[Nusa]

I've actually got a motherboard with that exact symptom...it won't fire up the power supply. But if I short the green wire to a ground wire, it fires up fine and the computer works properly in every other respect.

I'm sure I could fix it if I tried, but since this computer normally runs 24/7 anyway (it's my p2p server and media array), I just installed a shorting wire on the back of the connector as a permanent solution. There's still the hard switch on the power supply for those rare times I want a total shutdown.

To the OP, I suggest testing your old power supply in the same way you've been told to test the new one. Based on your current symptoms, I'd guess that wasn't the point of failure and there's nothing wrong with it.

[sony mavica]

I've actually got a motherboard with that exact symptom...it won't fire up the power supply. But if I short the green wire to a ground wire, it fires up fine and the computer works properly in every other respect.

I'm sure I could fix it if I tried, but since this computer normally runs 24/7 anyway (it's my p2p server and media array), I just installed a shorting wire on the back of the connector as a permanent solution. There's still the hard switch on the power supply for those rare times I want a total shutdown.

To the OP, I suggest testing your old power supply in the same way you've been told to test the new one. Based on your current symptoms, I'd guess that wasn't the point of failure and there's nothing wrong with it.

how would i do green wire to a ground wire?

[rs20]

how would i do green wire to a ground wire?

http://www.wikihow.com/Check-a-Power-Supply -- Start at step 3 if you already have the PSU out of the computer. And then, step 8 -- if you have a multimeter handy, you can actually check voltages.

[shteii01]

I've actually got a motherboard with that exact symptom...it won't fire up the power supply. But if I short the green wire to a ground wire, it fires up fine and the computer works properly in every other respect.

I'm sure I could fix it if I tried, but since this computer normally runs 24/7 anyway (it's my p2p server and media array), I just installed a shorting wire on the back of the connector as a permanent solution. There's still the hard switch on the power supply for those rare times I want a total shutdown.

To the OP, I suggest testing your old power supply in the same way you've been told to test the new one. Based on your current symptoms, I'd guess that wasn't the point of failure and there's nothing wrong with it.

how would i do green wire to a ground wire?

Paper clip.

[Avacee]

If you don't feel confident sticking wires into the PSU's connector then search eBay/Amazon/whoever for "atx checker" - less than £5 in the UK, probably similar in NZ.
This will also check the drive, floppy and GFX connectors.

Something like:  http://www.ebay.co.uk/itm/LED-20-24-Pin-PSU-ATX-SATA-HDD-Power-Supply-Tester-Checker-Meter-PC-Computer-DG-/122340643319
or (shinier!):  http://www.ebay.co.uk/itm/Computer-PC-Power-Supply-Tester-Checker-20-24-pin-4-SATA-HDD-ATX-BTX-Meter-TG-/262673970509

[RayRay]

Two things you should do:

1. Using a multimeter, set it to the DC Volt mode (if autoranging), or 20 DCV (if manual ranging)
On the main (24PIN) PSU connector (while it's still plugged in to the motherboard), stick the black probe inside one of the black wires, and the red inside the purple. It should provide a 5V output at all times (as long as the on/off switch of the PSU is set to on)
this is the standby power the motherboard receives from it.
If it gives significantly less voltage than 5V, then that would clearly be a bad indication.

2. Remove the power cord, disconnect the 24PIN connector from the motherboard, and jump start it (link between one of the blacks to the green)
You could simply use a wire that is stripped on both ends, or a metal paperclip (if using a metal paperclip, make sure the connector is placed under a non-conductive surface, such as a piece of cardboard), put the power cord back in, and see what happens.
To put it simple though, if it doesn't turn on, the PSU is bad and has to be replaced, but if it does turn on, then you got a few different possibilities:

A) Still could be a bad PSU (check the gray wire on the 24PIN), it should provide a 5V output while powered on (which is also the "all clear" signal for the motherboard)

B) Could be a bad power button on the case, to test this, simply switch between the power/reset wires on the motherboard.
This would enable you to use the reset button as the power button. If your case has no reset button, you could simply cut the wires of the power button a bit above the connector, strip em, and twist em together (to create a power on signal), if this would not make a difference, just put it together again and use electrical tape, simple enough.

C) Could be a short between the motherboard to the case, try removing the motherboard from the case and placing it on a piece of cardboard.
If the problem still remains, then the motherboard is dead.

Good luck!

[sony mavica]

ok i tried the old psu connecting it to the 24 pin connector computer fans turned on but then the computer turned off after about 3 seconds then i took the power cable out of the old psu and put it back in and it would turn on for a second  after 3 tries turning power supply off and on i got the computer to stay power on  left it running for like 2mins when i went to the toilet  then i plugged new psu 24 pin connector in and plugged in the power cable to the new psu and powered on the computer fans and everything came on fine but i forgot to plug the cable in by the fan so i turned it off and plugged it in tried turning the computer back on with no luck after trying a couple of times with the new psu

[RayRay]

ok i tried the old psu connecting it to the 24 pin connector computer fans turned on but then the computer turned off after about 3 seconds then i took the power cable out of the old psu and put it back in and it would turn on for a second  after 3 tries turning power supply off and on i got the computer to stay power on  left it running for like 2mins when i went to the toilet  then i plugged new psu 24 pin connector in and plugged in the power cable to the new psu and powered on the computer fans and everything came on fine but i forgot to plug the cable in by the fan so i turned it off and plugged it in tried turning the computer back on with no luck after trying a couple of times with the new psu

Sounds quite confusing. So it now turns on (but powers off immediately) with the new PSU, or still not turning on at all?
Also, you might wanna follow the advice in my previous reply (near the end of the first page)
Apart from that, do note the fact that your video card (GTS 450) requires additional power (and has 6-PIN PCI-Express power input for this purpose, so make sure you plug it in!)

[sony mavica]

ok i tried the old psu connecting it to the 24 pin connector computer fans turned on but then the computer turned off after about 3 seconds then i took the power cable out of the old psu and put it back in and it would turn on for a second  after 3 tries turning power supply off and on i got the computer to stay power on  left it running for like 2mins when i went to the toilet  then i plugged new psu 24 pin connector in and plugged in the power cable to the new psu and powered on the computer fans and everything came on fine but i forgot to plug the cable in by the fan so i turned it off and plugged it in tried turning the computer back on with no luck after trying a couple of times with the new psu

Sounds quite confusing. So it now turns on (but powers off immediately) with the new PSU, or still not turning on at all?
Also, you might wanna follow the advice in my previous reply (near the end of the first page)
Apart from that, do note the fact that your video card (GTS 450) requires additional power (and has 6-PIN PCI-Express power input for this purpose, so make sure you plug it in!)

after trying the old psu the new psu turned on once but after i turned off the computer to plug in the cable i can't get it to power on again with new psu