PC won't power up? Any suggestions

CharlieRabbit

Folks,

My aunt's PC won't switch on. I changed the power cable (verified that it worked on the monitor) and it didn't make any difference. Nothing comes on when I plug it in. I checked the fan built into the PSU but no joy.

I suspect that it's the PSU but I opened it up and I can't see any damage and the fuse inside looks ok. I know it could still be busted. The only other thing I can think of is the switch but I can't get at it. It's build into the front panel.

A PC at work last year got damaged after a power surge. We had to replace the PSU. Before I go and buy another can anybody suggest a way to confirm that the PSU is the problem?

By the way, I can't find any wires going from the PSU to the switch at the front. Does it go via the motherboard or something?

Cheers folks.

Charlie

majiktripp

Remove the ram and try to turn it on,if it comes on and starts beeping at least you have narrowed it down to the Ram itself.I wouldnt rush into buying a psu as its not a guaruntee that this will fix the problem......

123

Very possible its a loose connector or something
Or otherwise the easiest option is dump the pc in a tip and buy new

Mr. Presentable

start it with the case open. Do the fans spin?

CharlieRabbit

Thanks for the responses folks.

nipplenuts, the fans don't spin at all. It's dead as a door nail when I switch it on.

How could the RAM affect power going into the machine? It's not that doesn't boot. It's not powering up. No beeps and no fans moving.

The only loose cable I can think of is from the on/off switch to the PSU. I can't get at the on/off switch.

CharlieRabbit

Are all PSU's a standard size?

I might be able to get my hands on a decommissioned DELL. It's a 300 watt.

TommyGun

CharlieRabbit,
Even when the power is off but still plugged in, a LED on the motherboard should be lit. Check this.

If this does not work ask the following questions:
When did it stop working, what was been done at the time?
How long has the system not working.
How old is the system.

Just to check that the problem it is the PSU. I would remove all peripheral hardware , modem, HDD cable, CD ROM etc. and try to power.
If this still does not boot please reseat the Processor and RAM.

If the system is still completely dead then it is most likely the PSU as if there is a component fail there is usually some sign of life.

Gurgle

CharlieRabbit wrote:

By the way, I can't find any wires going from the PSU to the switch at the front. Does it go via the motherboard or something?

Unless its truly ancient it'll be a soft-boot.
The power switch is just connected to a pair of pins on the motherboard.

If you look at all the connectors coming from the front of the box to the motherboard, they should be marked 'HDD' 'RST' 'PWR' etc. Make sure these are all connected. The motherboard should have matching markings at the pins.

I assume it used to work. Did anything happen to it ?
Dropped? kicked?

cynos

1.No light from LED on Motherboard at all.
2.Fans dont even flinch when power cable plugged in<fan on CPU>
Deffo PSU or dead motherboard
replace PSU, most shops will take it back if it wasnt the PSU

CharlieRabbit

Thanks for the responses folks. I don't know what might have happened to damage the PC. It's my aunts and I found it a couple of weeks ago that it hadn't been working in a while.

I'll try out your suggestions tonight. Do any of you know whether a PSU from a DELL might work? The PC is unbadged. It was bought off a guy who builds the PCs himself.

Mr. Presentable

Almost certainly the power supply. gline on Boards has a 350 watt one for €15.00 for sale

http://www.boards.ie/vbulletin/showthread.php?t=2054897710

Gurgle

CharlieRabbit wrote:

Do any of you know whether a PSU from a DELL might work?

Probably not.

Dell go out of their way to use components with non-standard fittings and connectors so that they are the only spare-parts suppliers for their systems.

timeout

If you got a multimeter you can confirm it easily. See:
http://techrepublic.com.com/5100-1035-5566528.html

rogue-entity

Gurgle wrote:

Probably not.

Dell go out of their way to use components with non-standard fittings and connectors so that they are the only spare-parts suppliers for their systems.

Surly that should be illegal, a) it is Vendor Lockin and b) It could be construed as a barrier to trade.

I would hedge a bet that it is the PSU (although it could still be the mobo).

Gurgle

rogue-entity wrote:

Surly that should be illegal, a) it is Vendor Lockin and b) It could be construed as a barrier to trade.

Not at all.
You can't put the a Nissan clutch in a Toyota, although they do the same job.

CharlieRabbit

Hey Folks,

Bought a new PSU in Peats today (25 Euro for 350 Watt) after reading your suggestions. Screwed it into the case and plugged the PSU leads into the motherboard, hard drive, floppy and CD drive. Plugged it in to the wall socket and flicked the switch. Not a dicky bird.

The fan didn't move in the PSU at all. No sound, nothing. Should the PSU fan come on when it's plugged in and the PSU switched on?

I unplugged the PSU from the motherboard but no joy.

Any ideas?

L31mr0d

Easiest way to test a faulty PSU is the paper clip trick, which will let you know if its the motherboard that isn't turning on the PSU or if the PSU is bust.

If you have a fan that connects up to the PSUs molex connectors, or a multimeter or something that will let you know there is electricity on the connectors (preferably not your finger ) then do this trick:

psu paperclip trick

It will start up the PSU without the Mobo, then have something that you can see visably working on one of the connectors. If the fan in the psu isn't moving its usually a good sign that the PSU is kaputski, but not always, so check that you are getting voltages on the output. If it is broken, don't attempt to fix it, just buy another one.

andy1249

New PSU didnt help so the problem must be further up the line , check the fuse in the mains lead , ( cannot believe that that hasnt been mentioned in this thread yet !! ) , try another mains cable , if that doesnt help check that the mains socket you are plugged into is working , try some other appliance on it !!

gamer

a psu can power a motherboard ,even when fan is still,not moving.maybe its time to buy a mobo, at least get 1 with pci express slot.

CharlieRabbit

L31mr0d, thanks for the response. Why didn't I get talking to you before I forked out on a new PSU!!!:mad:

The paper clip test started the PSU I thought was broken. Well, the fan started so I presume it's working.

So could it down to the switch or the motherboard?

Any help greatly appreciated.

Esel

andy1249 wrote:

New PSU didnt help so the problem must be further up the line , check the fuse in the mains lead , ( cannot believe that that hasnt been mentioned in this thread yet !! ) , try another mains cable , if that doesnt help check that the mains socket you are plugged into is working , try some other appliance on it !!

See first post. The lead was checked.

andy1249

Oooops, Apologies , I'll be more attentive in future , sorry !!

ChRoMe

Sounds possibly like the motherboard is not raised off the case enough. Ensure it is not making contact with the case

the_syco

CharlieRabbit wrote:

It's my aunts and I found it a couple of weeks ago that it hadn't been working in a while.

OK. Ask her when she last used it. Also ask if she remembered was the weather bad around then? If she's down the country, its possible something got fried by lighting. If the modem is a sperate card, remove it, and look for damage. Often, this part shows damage, and this would be your first clue.

CharlieRabbit

The PC was affected by a power surge before. Lightning burnt out the modem card a couple of years ago. I replaced it and it worked fine. It was the first thing I checked this time.

It could have got another blast but the modem card looks fine.

groundedplane

The easist way to test a PSU is to remove power cable from motherboard, find the green and black wires and join them using a paperclip. Plug in power cord, If PSU is working , the fan will kick of, if not, nothing will happen and if this is the case you can assume PSU is bollixed.

CharlieRabbit

Thanks for all the posts folks. I have confirmed that the PSU is working using the paper clip test on the black and green cables of the motherboard power cable.

I took out the RAM and the modem. Tried again and still no joy. Do any of you know how to test the switch? As I said earlier I can't get at the switch cause it's built into the front panel of the case and I can't see how to remove it.

If I can short the switch cables like I did the PSU green and black cables I could rule that out too.

Cheers,

Charlie

TomCo

Can you see where the switch connects to the motherboard? It's a little white two pin plug going over two pins (I think its the second and third pins on the left row) on a row of pins in the corner of the board.



Pins seen in the bottom left of this pic.

Check is the plug on tight and try to power up, failing this remove the little plug and short the two pins it was covering with a screwdriver.

At least this will rule out the power button as being the fault.

Sid71

Had a problem like this it had me baffled! turned out it was that little cmos battery! try this

Bobby_Digge

If there is no green LED on the board there is no power going to it and because the paperclip trick worked by spinning the fan it looks like the board cheaper buying a good second hand machine than a new systemboard

the_syco

Bobby_Digge wrote:

If there is no green LED on the board there is no power going to it and because the paperclip trick worked by spinning the fan it looks like the board cheaper buying a good second hand machine than a new systemboard

Actually, a new mainboard (systemboard?) may just work out at 50 odd euro. You'll see, in big letters, the name of the motherboard (letters and numbers, usually), and print it up here, and I'll check for you on how much a new mobo would cost ye.

CharlieRabbit

Thanks again for all the posts folks. I really appreciate it.

There is no LED light on the motherboard at all.

I tried shorting the on/off pins last night but no joy. I got the front panel off the case last night and got the right wires.

I'll check the motherboard brand etc tonight.

Could it be the CMOS battery Sid71? Haven't tried that.

timeout

Doubt its CMOS battery. Even if its dead the default values are loaded and a cmos checksum error comes on screen if the pc gets powered up but yours is not even doing that.

Also if its a P3 slot type processor taking this out and placing it firmly back in can sort this problem out. They sometimes work their way lose and can cause a short.

Snowbat

** Warning - proceed with extreme caution at your own risk **

You can also use the paperclip trick when the power supply is connected to the motherboard by sliding the paper clip legs in briefly on the wired side of the connector. Don't leave the paper clip inserted for more than a few seconds or the power supply will shut down (same as holding in the front panel power button on an ATX system).

If the machine boots, power down, locate the 2 wire cable from the front panel power switch and follow it to the motherboard header pins. Try powering up the machine by either shorting this 2 wire POWER SW connector briefly with a paperclip (if you can squeeze the paper clip legs into the connector) or remove the connector and briefly short the two header pins on the motherboard that the connector was on

If the machine powers up from both locations, you have a bad front panel switch/cable.

If the machine powers up only from shorting the power supply connector, you have a bad track on the motherboard somewhere between the power supply connector and the POWER SW header.


Edit: I should add that there are many other reasons for a working power supply not to start, such as a short from the 12V or 5V rails to ground, or a fault in a card, USB device, drive, or the motherboard.

Inspector Gadget

In case it helps, the fact that the PSU switches on doesn't mean that it's actually working. Some motherboards check the state of the PWR_OK pin (the grey wire) to see if the power supply thinks things are okay before it spools up - though as far as I know most soft-start motherboards take a fraction of a second to figure themselves out after you apply power, during which time the fans often judder a little.

Can I confirm that you found an LED on the main board, but that it did not light when you plugged the PSU into the mains? Or is it that you can't find an LED?

While I know that these may sound like stupid questions to ask, here goes:

1. If there's a power switch on the back of the PSU, was it set to 1/On?
2. If there's a voltage range switch on the back, was it set to 230V? (People looking at the techrepublic link above, take note)
3. Was the PSU firmly connected to the motherboard (did the little locking clasp on the plug slip over the matching bump on the socket?)
4. If there's an ATX12V socket on the board (looks like the main ATX power connector, only it's a 2x2 pin socket), is that connected?
5. Did you remember to actually push the power switch on the front of the PC after all this? (It's easier done than you'd think... or maybe that's just me)
6. Did you try disconnecting everything except the processor and one stick of RAM, and seeing if anything happens?
7. For that matter, are the RAM stick(s) and processor correctly seated in their slots (particularly relevant for slot form-factor processors (PII/PIII/Athlon), as someone mentioned earlier)
8. Is the on-board speaker connected? (This one has caught me out a few times - on systems where the buzzer isn't soldered to the board, the board could be trying to report a fault with beep codes, only I'd never hear it because there was no speaker connected... doh!)
9. As there was a modem connected, are there any burst/burnt components on the modem card? You could be dealing with a lightning strike here.
10. Has anyone else been inside this thing since it stopped working?

That's my shopping list of things to look at... good luck.
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