installed new PSU in my computer it won't turn on :( - Page 1
Forum section: electronics / general

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 05:18:05 am
content: 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

author: DimitriP
author_rank: Super Contributor
timestamp: April 03, 2017, 05:31:03 am
content: 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 ?

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 05:36:58 am
content: Quote from: DimitriP on April 03, 2017, 05:31:03 amyes 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

author: Halcyon
author_rank: Unknown
timestamp: April 03, 2017, 05:38:23 am
content: 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.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 05:51:44 am
content: Quote from: Halcyon on April 03, 2017, 05:38:23 amok i will have a look now

author: Roeland_R
author_rank: Regular Contributor
timestamp: April 03, 2017, 05:53:06 am
content: Check the battery on the motherboard. I have seen bad ones preventing boot.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 05:59:29 am
content: Quote from: Roeland_R on April 03, 2017, 05:53:06 amthanks 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

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 06:07:21 am
content: replaced it but computer still will not turn on

author: rs20
author_rank: Super Contributor
timestamp: April 03, 2017, 06:15:49 am
content: Thou shalt test voltages!Completely unplug the PSU from everything else (except for the mains plug, of course) and check that+5VSBis 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 thattellsthe 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).

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 06:26:02 am
content: Quote from: wilfred on April 03, 2017, 06:18:21 ami gave the computer a good clean already

author: Halcyon
author_rank: Unknown
timestamp: April 03, 2017, 06:32:47 am
content: Do the fans spin up when you power on? Do you get any error beeps?

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 06:38:33 am
content: Quote from: Halcyon on April 03, 2017, 06:32:47 amnothing at all happens only the green light on the motherboard comes on

author: Brumby
author_rank: Unknown
timestamp: April 03, 2017, 06:43:30 am
content: Nothing happensat all? - not even with the fan on the PSU??I'm inclined to try this before doing anything else...Quote from: rs20 on April 03, 2017, 06:15:49 amIf 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.

author: Halcyon
author_rank: Unknown
timestamp: April 03, 2017, 07:01:29 am
content: Quote from: blueskull on April 03, 2017, 06:51:44 amThat! Do as this man says.

author: Red Squirrel
author_rank: Super Contributor
timestamp: April 03, 2017, 07:22:35 am
content: 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.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 07:25:24 am
content: Quote from: Red Squirrel on April 03, 2017, 07:22:35 amthe power button works

author: Nusa
author_rank: Super Contributor
timestamp: April 03, 2017, 07:29:18 am
content: 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.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 07:37:44 am
content: Quote from: Nusa on April 03, 2017, 07:29:18 amhow would i do green wire to a ground wire?

author: rs20
author_rank: Super Contributor
timestamp: April 03, 2017, 08:28:24 am
content: Quote from: sony mavica on April 03, 2017, 07:37:44 amhttp://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.

author: shteii01
author_rank: Frequent Contributor
timestamp: April 03, 2017, 08:36:23 am
content: Quote from: sony mavica on April 03, 2017, 07:37:44 amPaper clip.

author: Avacee
author_rank: Unknown
timestamp: April 03, 2017, 09:59:49 am
content: 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-/122340643319or (shinier!):http://www.ebay.co.uk/itm/Computer-PC-Power-Supply-Tester-Checker-20-24-pin-4-SATA-HDD-ATX-BTX-Meter-TG-/262673970509

author: RayRay
author_rank: Frequent Contributor
timestamp: April 03, 2017, 03:09:45 pm
content: 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!

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 11:00:51 pm
content: 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

author: RayRay
author_rank: Frequent Contributor
timestamp: April 03, 2017, 11:36:22 pm
content: Quote from: sony mavica on April 03, 2017, 11:00:51 pmSounds 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!)

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 03, 2017, 11:40:38 pm
content: Quote from: RayRay on April 03, 2017, 11:36:22 pmafter 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

author: RayRay
author_rank: Frequent Contributor
timestamp: April 03, 2017, 11:45:41 pm
content: I see.This is definitely starting to sound like a motherboard problem.But as said before, you should follow the instructions in my initial post in order to rule out other factors:https://www.eevblog.com/forum/chat/installed-new-psu-in-my-computer-it-won't-turn-on-(/msg1177596/#msg1177596I gave you some very simple instructions on how to test the PSU, power button,and a possible short between the motherboard to the case.Edit: You could also test the power cord (while completely disconnected) for continuity across all 3 points from end to end, and check that neither is reaching each other (shorting). I highly doubt the power cord is the issue, but worth a check.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:08:58 am
content: i now can get the new psu to turn on fine if i unplug the 8 pin connector by the cpu fan

author: RayRay
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:12:25 am
content: That 8PIN plug provides power to the CPU.And CPUs very rarely go bad, so it's clearly a motherboard issue.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:16:52 am
content: Quote from: RayRay on April 04, 2017, 12:12:25 ami ust noticed on of the clips on the cpu fan that holds it down is broken

author: RayRay
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:23:29 am
content: Could you take some pics?Also, is there something you forgot to mention? Did you in any way fiddled with the CPU fan before any of this started?

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:27:50 am
content: Quote from: RayRay on April 04, 2017, 12:23:29 ami had problems last year around september once i cleaned my computer of dust ect and cleaned the cpu fan ect and put new paste on it the pc had no problems till around 2 or 3 weeks ago

author: RayRay
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:30:23 am
content: That doesn't fully explain it though!Clips definitely don't break on their own.You didn't do any other "physical" activities in there shortly before the problem started?

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:39:15 am
content: Quote from: RayRay on April 04, 2017, 12:30:23 amnope

author: RayRay
author_rank: Frequent Contributor
timestamp: April 04, 2017, 12:48:03 am
content: Okay, maybe I got a bit caught up on that one.Anyhow, I'd say it probably got broken a while back (while you were servicing the cpu fan).But this is likely a moot point (if it was sitting relatively well and worked fine for several months then it couldn't have been too much of an issue)And I'm starting to get a very clear picture of what happened here!Seems that at some point, the CPU fan failed, you couldn't have known, and the heat caused damage (to the cpu, motherboard or both).I'd say you should be looking at getting a combo of a new motherboard/cpu/ram.I could help you pick em if you want to.Also, just a word of advice, if your case doesn't have a side window, then better get one that does (and put it next to the monitor where you can actually see thru it!) this could give you a heads up next time.

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 01:46:05 am
content: so the cpu could be bad would a will FCLGA1155 socket i3 cpu i know works fine work on LGA1155 cpu socket?do you think switching the cpu would help?

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 02:17:53 am
content: Quote from: blueskull on April 04, 2017, 02:11:27 amshould i swap i7 cpu for the i3 i know that works and to see if the i7 cpu is dead?also i plugged in my old psu with the 24pin connector and the 8 pin connector and computer powers on for like 1/2 seconds and then powers off again and if i try turning it on again it just keeps switching off in the half a second

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 02:35:02 am
content: Quote from: blueskull on April 04, 2017, 02:27:25 ami don't think any of the solder joints snapped off as i can still get it to power on with the 8pin connector plugged in with the old psu just not the new onethis problem is so annoying im about ready to chuck this pc out the window

author: sony mavica
author_rank: Frequent Contributor
timestamp: April 04, 2017, 02:42:08 am
content: Man i am so dumb it turned out i never noticed another cable on the new psu and that i had plugged in the wrong pin connector and now pc boots up finethanks for all the help guys

author: DimitriP
author_rank: Super Contributor
timestamp: April 04, 2017, 04:30:53 am
content: QuoteIt always sucks when the wrong connections are good !