Hi

I am asking if anyone can tell me what is wrong with my PC given the following problems. If I try to reboot either from the PC button or through the OS the PC locks up. Occasionally when switching on it also locks up. In either case the only remedy is to switch the PC off at the wall socket and wait a short time. Generally this solves the problem until the next time.

As I undertsand it for some reason it is not activating the POST system and as this is ROM buit into the motherboard it looks to be terminal e.g. motherboard replacement.

Does anyone know differently?

grabro

I would first try to replace the power supply.

Hi there,

could be the motherboard in fact, but that's not the only possibility. It could also be the power supply. If one of the fans (power supply, CPU) isn't running or the HDD won't spin up, the power supply would be the prime suspect. Try to open the CD/DVD tray while the PC is stuck. if it doesn't respond, that could also be a hint to a power problem.

How old is your PC's mainboard? You could examine the elcaps (electrolytic capacitors). They're small aluminum cups with a plastic sleeve, most of them about the diameter of a pencil or smaller. Look closely at the bare metal top. If it's bulging or already popped (so that there's a thick white liquid, maybe already dried off), it's time for a new board - except you know a very skilled electronics technician who could replace them for you. But if the board is older than, say, five years, it's probably not worth the effort.

There are numerous elcaps inside the power supply too, much bigger ones, and they could be aged the same way. But you shouldn't try to open the power supply itself; there's hazardous voltage inside, even for a while after disconnecting from mains!!

[X] Doc CPU

Failure to start/POST can be caused my many things. Motherboard/BIOS issues are the most common, but it can also be caused by problems with power supply, memory, video card or even some add-on/onboard components.

Power supplies are ~ €30. So would a set of capacitors be. It's clear, Cascade9, that you are in the business for love and not for money. Don't forget to make the rent :-)

On the topic, there's a power good line somewhere - a green one (Cascade9??) I think, on the plug. That switches low if the power is ok according to the cpu. The other obvious suspect is bios/cmos backup or even resource assignment stuff going awol.

Does it write anything to screen at all in the fault condition?

Hi there,

a set of suitable capacitors would be rather around 5EUR, 10 at most. But it's some tedious work to exchange them without causing more damage, and a professional repair workshop could easily charge you ~100EUR for the job. Not worth the effort, anyway.

Not quite correct. The "Power Good" line on an ATX power supply is usually gray, and IIRC it was purple on the old AT power supplies (you know, those with the two 6pin jacks labeled P8 and P9). And the signaling of "Power Good" has nothing to do with the CPU; rather, this signal is set to +5V by the power supply itself as soon as all output voltages are stable (see schematics in Wikipedia).

I understood the OP that way that either the computer powers up normally or nothing happens - that's why I suggested to check if fans were running, and if HDD and CD/DVD drive were on power.

[X] Doc CPU

It wasnt me would brought up caps, but I do replace caps. Normally only on motherboards, I'd rather not bother with power suppies, its not worth it for several reasons. Though I would possibly recap a PSU if it was something I couldnt replace easily (eg, 250watt+ AT PSUs)

I've seen some people charge huge amounts for recaping, but I wont. Apart from a few times I've had people need something recpped for professional reasons where I will charge 'industry rates' I normally dont charge that much, it just feels wrong.

I probably am doing hardware for love, not money, but the warm fuzzy feeling of booting a new, or better yet fixed system is addictive.

The green line is the 'power on' line. You connect the green line and any black line to 'jump' the PSU into starting. Not a good idea in many cases, but its a handy trick for the workbench.

Hi there,

oh well, it's a good idea to quickly check why a PSU wouldn't start up: Just short the Power-On line.
If the PSU starts up then, the problem is somewhere on the mainbaord; if it still doesn't, it's the PSU itself.

Plus, this is essential if you're gonna use an ATX PSU for something other than a computer. ;-)

[X] Doc CPU

Like Doc CPU says,"How old's your Motherboard?" If it's been running for some time perhaps the CMOS battery is low and you've got some sort of corruption of the CMOS. OK, you'd usually get it falling back to a default status with a date in the stone age. You'd probably get the same symptoms each time it booted but...

Pop the coin battery on the board, wait about a minute and then put it back. Check it with a meter if you can, it should be about 3.0 to 3.6 volts.

Reboot, this time it WILL be back to default and you'll need to set the date/time in the BIOS and possibly change the boot order and primary boot device.

Might be worth a shot? Cheaper to check than buying a new PSU in the first instance!

Play Bonny!