Help! PSU problem?

sibx · 10 Oct 2006 at 17:55

Hi,

I have a strange problem that I just can't seem to solve.

I've got two PCs, one upstairs and one down. A while back we had lightning strike the phone cable and it wrecked the network side of things in my PC upstairs, so I replaced the network card along with the router and phone. Problem solved.

Roll on about 2 months, and the PC upstairs stopped working altogether, I couldn't get it to boot past the POST screen. After trying a few different things, I figured it was probably the motherboard, so off I went to ebay and bought a new one. This fixed the problem again, and I could boot up fine.

Roll on to 2 weeks ago and the PC died yet again. I was sat using it when I heard a pop and then it powered off. Hitting the power switch does nothing, no fans spinning or anything, and the USB devices that are connected do not receive power (previously they did, so the optical mouse would always have it's LED on even with the PC shut down), so I figured it was probably the PSU.

I tried switching the PSU around from my downstairs PC to the dead one, and that didn't work. So I tried using my PSU in the dead PC in the PC downstairs that did work, nothing. So now I thought maybe the PSU had blown and taken the motherboard with it at the same time, oh yay!

Anyway, I put the 'working' PSU back in the 'working' PC, and now that won't power on either, and like the other, no power is going through to USB devices.

So, I now have two PCs, both of which will not power up in the slightest. Roll on to today, and I received a motherboard/cpu bundled in the post, fitted it all together in the previously working PC, along with a new power supply, and nothing. It won't power up.

Any ideas? I'm tearing my hair out as it's costing me a fortune in spare parts.

sibx · 10 Oct 2006 at 18:11

Also, I've tried both PCs from two different mains power sockets and with two different kettle leads. The power switch and everything is connected up properly on the motherboard and all cables are fitted correctly.

I'm really stuck with this one :confused:

hip · 10 Oct 2006 at 18:21

When the original psu died it was prolly some resistor or cap that could no longer limit the voltage, which fried your mobo. This prolly fried the other mobo when you put it in the machine - the stuff you describe would still make sense - if you instantly fried the mobo the usb devices wouldn't see any of the power as you'd blow the power electonics on the board first.

Quite why this would then melt your original psu is beyond me. What's the most a mobo gets, 15a? Even if the mobo somehow directed the power back to your working psu, wouldn't it have enough protection not to die straight away?

shame you don't have one of those 240v plug things that monitor how much power has moved through the socket in amount of time x.

Sounds like the next thing you need is a new psu! and a surge protector :]

and maybe an electrician! No chance your house power supply is fubared?

jesus this must be really annoying :]

sibx · 10 Oct 2006 at 18:31

What I don't get right now though, is how I have just put a new motherboard, CPU, memory and psu together in a case, and yet it still won't power up :S

Tried it with different mains sockets plus different kettle leads. My laptop works fine on both of these sockets.

I just can't think what it could be now. I'm angry enough at all the money I've wasted on this. Could the actual power switches get damaged some how? I can't see how they would but it's one of the last ideas I have haha.

sibx · 17 Oct 2006 at 20:32

Digging up this thread rather than opening a new one.

I've determined that my old power supply was blowing the fuses in my mains kettle leads. So I replaced the fuses and the power supply. I now have one operational PC and one which still won't work.

The one which doesn't work was the lightning damaged one. Is there any chance the power switch on the case could have been damaged? Remember this is a new motherboard as well so I don't think it should be that which is damaged.

Is there any way I can buy a new power switch, even if it means leaving the side of the case off temporarily until I can sort a cheap case out or something. Any cheap ideas and advice are welcome at this stage!!

Avalon · 17 Oct 2006 at 23:56

A well known high street electrical component store could probably sell you a switch for under a quid but the exact type depends on your case or if you don't mind drilling a small hole you could have a retro toggle switch

Just use screwdriver or jumper to bridge the connection and turn it on for testing, only needs shorting for a seccond or so to power up.

sibx · 23 Oct 2006 at 15:32

Avalon said:
A well known high street electrical component store could probably sell you a switch for under a quid but the exact type depends on your case or if you don't mind drilling a small hole you could have a retro toggle switch Just use screwdriver or jumper to bridge the connection and turn it on for testing, only needs shorting for a seccond or so to power up.

Yep, figured out the shorting bit and it does indeed work. Nobody believes me when I tell them I have to hotwire my PC to turn it on but it's funny nonetheless.

I'll go check in said high street store tomorrow, thanks.