Where's the power gone ?!?!

  Heefie 18:31 30 May 2005

I set up an new (second hand) PC in my daughter's bedroom last night, configured it to Win2k & it's been running fine.

She went out today and the PC was, apparently, left switched on.

During the day we had one of the fusebox switches, one that affects her room, "trip".

When she got home, she came down and told me that the PC was dead, though the monitor & speakers running from the same extension lead were fine.

I took the power lead from the monitor & tried the PC Power lead & the monitor came on, so knowing that the lead that was originally in the monitor was OK, I plugged this into the PC ... I got a blue spark, a crackle & the same fusebox switch "tripped".

So, the first question is, even though nobody was in the room where the PC was, and it wouldn't have been doing anything as nothing is set up to run automatically yet, could the PC have caused the power problem ?

I then reset the fusebox, & tried both leads again to make sure they were both still 'live' & put one into the back of the PC ... nothing, no hint of life.

I therefore put in a brand new PSU that I have & plugged the power back into the PC (with nothing else attached, no mouse, no keyboard, nothing) and there is no hint of life, absolutely nothing at all, yet I know the lead is 'live' ...

So my second question is ... what do I check, and how, to find where the problem is ?!?! Would the PSU show any kind of life when I plug the mains lead in (I don't think so, but why the hell do they not just have a small light on them so you can tell if they're working OK ?!?!) ? Surely I wouldn't be unlucky enough to have a faulty brand new PSU ... though I wouldn't be surprised, !!!

When I turn the PC on at the button, will it even attempt to power up if nothing else is attached ? Surely it should try & power up & then fail.

We've had no adverse weather today (I'm in Dublin) so I'm sure the problem hasn't been a "power spike", but could it be a motherboard problem .. surely not ?!?!?

Any help appreciated ...

  DieSse 18:37 30 May 2005

If the PSU blew (as seems likely) - then they sometimes cause extensive damage to the system itself - and can kill the motherboard - which would prevent the system showing any sign of life at all.

Look on the motherboard to see if any LEDs light up - newer m/bs have them.

And see also of any fans are spinning, or try to.

Just check if there is a mains switch on the back of the new PSU - some have them!

Looks like real bad luck - did you get any sort of guarantee?

  skeletal 19:43 30 May 2005

Oh dear, what a disaster!

In addition to DieSse's good suggestions, do you have any CD drives etc? Do they work (i.e. do the drawers open?). If so, this would suggest at least part of the new PSU is working (it is possible, but unlikely, that a new PSU is faulty).

Unfortunately, if you have been unlucky, it is possible everything in the computer has been fried. I do hope this hasn't happened. With luck, you have just forgotten to turn the new PSU on (I have done things like that!).

After these preliminary checks, I would be checking everything with a multi-meter, but I expect you may not have much in the way of such test gear.


  Heefie 20:04 30 May 2005

Luckily it's not a new all singing all dancing machine, just an old second hand PC, but she's been waiting for this for months and it took me half of yesterday to get it up & running, adding a DVD drive & 2nd HDD, installing Win2k etc., etc., etc. ... she then loaded tons of music onto it ... which I hope will still be on the HDD ... and she rented a DVD to watch with her friend this evening !!!!!!!!

My main concern now, though, is why we had this problem with the electricity ... mind you, we rent this house and it was wired up by a cowboy, that's for sure ... I guess I should get some kind of plug protection in place ... more money !!!!!!!

There's definitely no spinning fans, whether there's any lights on inside, I'll look over the next couple of days, not so sure immersing myself into PC fixing would get me many Brownie points with the missus after yesterday !!!!!

Thanks for your input so far, and, no, I have no idea what a "multi-meter" is ... I enjoy building and tampering with my PCs, should I get one ?!?!?

  Joe R 20:09 30 May 2005


I had this same problem a year or so ago, and the main cause was not having a "surge protected Adaptor".

Luckily in my case it only blew the PSU, and after this was replaced, it worked fine.

  DieSse 21:13 30 May 2005

It may not have been a problem with your house supply at all - I've seen several PSUs which have just blown due to an internal fault - and taken out most of the insides of the PC at the same time.

If a PSU fails in some modes, no amount of external surge protection will save the internals of the PC.

Not all of them fail in this way, sometimes it's just the PSU that goes - sometimes it's the PSU and just some other items - sometimes it's virtually everything (seen 'em all ways).

Sorry it's not good news, but that's the real world I suppose.

  Totally-braindead 21:23 30 May 2005

Get a surge protector they are only about a tenner, it may not have saved the power supply as Diesse has pointed out it could just be bad luck, I built a PC for a friend a couple of years ago and after about 6 months the supply blew, little bits of glass in the inside of the case as it turned out it had a glass fuse soldered into the power supply board and it was this that blew, got a replacement power supply sent and it fired up no problem so hopefully yours will be the same.

  De Marcus 21:24 30 May 2005

Check the psu's internal fuse.

BUT only if your confident doing so, if not replace it as it's quite obviously gone, then, before you plug it in, buy a plug socket tester from homebase, B&Q, etc, and check your sockets for correct wiring, earth groung, etc.

  skeletal 23:26 30 May 2005

Heefie, please don't take this the wrong way, but if you don't know what a multi-meter is, I suspect you would struggle to understand how to use one to help mend a PC. Now that's not to say you couldn't learn of course, but it may take longer than a minute or two!

Their basic function is to check voltage, current and resistance (and other things if you pay enough) in electrical/electronic circuits. Thus, if you look for the right things in the correct places you can build up a picture of how a circuit is working (or not!); in your case, I would be looking at the output voltages of the PSU. For example, just thinking of the 12V output (the same applies to all outputs) if the 12V was much less than 12V...big clue! But the part that then needs more thought is, does the voltage reach 12V when the PSU has no load, then drops to near zero when the mother-board is plugged back in. If so, it indicates too much current is being drawn by the mother-board; a short circuit perhaps. Then I'd try to find the short using the resistance measuring part of the MM...and so on. (Having said all that, in today's world, it is often not worth trying to isolate a faulty individual component because it can take hours and you can buy replacement boards relatively cheaply.)

De Marcus suggests checking fuses; easy with an MM, open circuit it's blown, a few ohms and it's OK.

Personally, I do not know how any household can possibly do without a basic MM, but I have an electronics background so take what I say with a pinch of salt!

On the other hand you may get bitten by the electonics bug and a new, vast hobby awaits you! The so-called building of computers these days only consists of plugging a few boards together (which gives rise to enough problems itself of course); try actually building the boards! Many years ago, someone I knew wanted to REALLY understand how a microprocessor system worked so he soldered a processor up to some switches/gates/memeory and LEDs and by operating the switches could get it to light the LEDs in a programmed fashion. The big joke was, to make everything clear to see, the the clock speed was 1Hz, yes 3000 million times slower than today's computers!


  woodchip 23:39 30 May 2005

You should not switch a PSU on without it being connected to a Load as they are Switching PSU's and only work with a Load on them. the PSU can burn out if you try without it connected. The way to test is use the multi-meter to back probe the The main power plug from PSU to Motherboard when the Computer is Switched on. By putting the Red probe on back of pins and black probe to ground i.e Case. But you need the Pin out volts to do the Above. These I have got if you want to try. The Volts are only Low Volts From 5+ to 12+ volts

  Heefie 10:34 31 May 2005

I'm now ebaying for a new M/B with CPU & memory ... I don't think messing about with live electricity is my cup of tea ...

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