Computer Related > Problem powering desktop on Computing Issues
Thread Author: Mike H Replies: 16

 Problem powering desktop on - Mike H
Having spent a fruitless couple of hours searching on the internet for a solution to the power up problems with my old desktop, I thought it was time to ask the real experts :-)

The machine is about 13 years old. I had some intermittent problems with it booting up some 4 years ago, which I eventually discovered was the SATA controller, so I used an old PATA drive. It has an ATX motherboard, which unfortunately is a MESH proprietary one, and there doesn't seem to be any documentation available for it.

I successfully loaded Windows 7 and upgraded to Windows 10 about a year ago. It was pretty slow but fine for surfing and the odd spreadsheet, and seemingly totally reliable. It's only used as a backup machine, and not often, as I usually use a laptop.

During lockdown we tidied our study and move the desk, complete with desktop, a foot or so. Next time I tried to boot it up, absolutely nothing happened. It hadn't been physically touched except to be moved with the desk.

The LED lights up on the motherboard, which indicates power to the board, but I can't seem to measure any power on the 20-pin connector. Perhaps I'm being naive in expecting to?

I have reset the BIOS by removing the battery overnight, then installed a new one (battery that is).

I have tried powering it on with only one memory stick connected, and swapped memory sticks.

I have tried both shorting the pins on the motherboard for the power on button, and swapped the connectors with the reset button as suggested online.

I have unsuccessfully tried powering it on without the HDD and the DVD drives connected.

The bizarre thing is, that if I remove the 20-pin power socket and only connect the 4-pin connector that mates to it, the CPU fan will run and the HDD spin. If I connect either the 20-pin on it's own, or in conjunction with the 4-pin, we're back to square one, it's dead as a dodo.

Suspecting a power supply problem, I ordered a new power supply from Amazon and connected it today - but even when I connect just the 4-pin connector, nothing happens, which is different to the old PSU. I am not measuring any voltages on the new one either, even on pins which did show a voltage on the old one.

I'm still thinking it's a PSU problem, and the replacement one is faulty. Does this sound reasonable?

And finally, has anyone else got any ideas, because I'm stumped! I should say that my main area of expertise with PCs is as a pretty knowledgable user, but I don't have a lot of hardware experience, although I'm usually quite capable of poking around the innards when necessary.

 Problem powering desktop on - tyrednemotional
It could be almost anything, but if you want to eliminate problems with the new power supply, you'll probably need to do the "paper clip" test (if you haven't already).

It's not simple to test a PSU off-board without certain steps. A number of them may well require at least a small load before showing any life. (I've been there, got the T-shirt).

Various links on the web will detail the method - this is a reasonable one:

www.evercase.co.uk/PDFFilesandForms/HowToTestAnATXPSU.pdf

Note the advice to leave a load attached to the psu (on one of the other cables), a case fan should be fine.

(of course, you may already have done this).

Edited to add:

You have switched the new PSU on? ;-)

Last edited by: tyrednemotional on Tue 12 Jan 21 at 17:02
 Problem powering desktop on - Mike H
That explains the lack of readings on my meter. I'll give it a try tomorrow.

And yes, I have switched the PSU on ;-)
 Problem powering desktop on - Mike H
I've tested both power supplies using the link you gave me, many thanks! I get the same result with both, that is, the PSU fan runs, and the connected device runs (in the case the HDD). So I'll assume at this point that both PSUs are working. However, there's a note at the end of the instructions that say to leave the PSU overnight due to a potential for a high discharge, so that's effectively scuttled any further progress today. Never mind, we're in lockdown and I will have plenty of time tomorrow :-)
 Problem powering desktop on - No FM2R
Ignoring the second PSU and with limited expertise, it doesn't sound like a power problem.

If the fan isn't firing then I'd it's failing its tests somehow. The only time I had that it was dodgy memory.

Does removing all memory, or removing all disks, or removing everything except the motherboard itself change any reaction?

If not, then perhaps the motherboard itself has died.


 Problem powering desktop on - smokie
Yep, I'm with Mark on this, take all the memory out and you ought to get a beep code, or at least a screen message.

Likewise leaving the CMOS battery out should give you a screen prompt for date/time. I'm pretty sure no keyboard will usually also give you a beep code.disconnect keyboard to get a beep code.

I'm presuming you've disconnected all external peripherals, esp any USB devices?

Does the monitor ever go Live (on mine the on-off switch changes colour when it gets a signal).

If so you may have a BIOS splash screen obscuring a useful message that early in the start up process (though it sounds like it may be too early even for that). In the BIOS turn of any splash screen.

Must say, I'm also with Z, as in if it is the mobo it is probably past it's sell-by - you can pick up refurb machines reasonably cheaply these days (in the UK anyway!!).
 Problem powering desktop on - Mike H
I haven't tried booting it without the battery, and since starting the diagnostics with the screen, simply because absolutely nothing happens e.g. CPU fan doesn't run UNLESS only the 4-pin connector is connected. I can't help thinking that this is a clue to the problem? Definitely no beep codes and no external devices connected. I'll try booting it tomorrow with the monitor connected, but when the problem started there was no communication with it.

I'm not worried about replacing it if it doesn't work, it was only a Frankenstein machine built from bits of two desktops out of interest, and I don't actually need it, it's just a spare tbh.
 Problem powering desktop on - Mike H
All memory out, no beep codes.

CMOS battery out, no change.

Only peripherals connected were keyboard, screen, mouse, but the monitor never goes live.

You'll see from another post that I have tested the PSUs as per the link in tyrednemotional's post and they seem OK.

Increasingly looking like a motherboard problem, but the PSU testing info suggests that I should now leave the PSUs overnight due to the potential for a dangerous discharge, so I'll have to leave Z's suggestion until tomorrow.
 Problem powering desktop on - Mike H
I haven't tried starting it with no memory, I'll give it a try tomorrow.
 Problem powering desktop on - Mike H
I've progressively removed everything from the motherboard, leaving just keyboard, mouse and screen. No BIOS error messages on the screen, and the computer is not getting far enough to communicate with it.
 Problem powering desktop on - Zero
> The machine is about 13 years old.

Its time for a new one.
 Problem powering desktop on - Mike H
I don't really need it, so I won't replace it. It's just a challenge to get it going again. I took a 20 year old machine to the recycling centre a couple of weeks ago which was running XP perfectly well but incredibly slowly with IIRC 512MB RAM. It was too slow to do anything with, but it was a sad day when it went.
 Problem powering desktop on - Zero
Ok, if someone had brought it to me with a plea to see if it lives.

unplug everything, remove expansion cards, take out motherboard.

Remove the CPU, take off the cooler, clean off the old heatsink slime, replace with new. refit CPU and cooler (take care with anti static precautions and the pins on the CPU.

Clean the earth plane pads round the mounting holes on the back of the motherboard, clean the standoffs in the case, refit motherboard.

fit one stick of memory in one dimm slot, plug in keyboard monitor and your boot drive.

test.

(the earth plane pads is a common issue on older machines and it may explain why plugging in fans changes stuff, - spurious earth paths)
Last edited by: Zero on Tue 12 Jan 21 at 20:23
 Problem powering desktop on - Mike H
I've updated the rest of the thread with what I've tried today. You'll see that I have tested the PSUs and tried removing various items but with no success. The PSU test advises not touching tnhem until tomorrow, so the job then is to try your suggestion of removing it and cleaning the various contacts. I'm not sure what an earth plane pad us, but no doubt I will find out tomorrow when I clean them ;-)

Thanks for your suggestion, will update tomorrow. It still seems odd that it just suddenly happened....
 Problem powering desktop on - Zero
I'm not sure what an
>> earth plane pad us, but no doubt I will find out tomorrow when I clean
>> them ;-)

Its the plated area on the motherboard around the screw mounting holes. layers of motherboard are called "planes"
 Problem powering desktop on - Mike H
So, removed motherboard, cleaned up the pads with fine abrasive paper, reassembled. I found a couple of the screws were a little loose, and I was filled with optimism that I'd perhaps located the problem. But alas, no change on reassembly :-(

So all things considered, having tried most things known to man, does this probably mean that the motherboard has some sort of failure?

Looking at Wikipedia for ATX board specifications, it seems that my board is slightly smaller in one direction at 230mm, whereas the standard spec for a microATX is 244mm square. Is it likely that a standard microATX board would fit?
 Problem powering desktop on - VxFan
>> but it was a sad day when it went.

I know what you mean, but there is something satisfying about the noise it makes when taking it to the tip and throwing it into the WEEE Disposal bins. Especially when the bins are near empty and thrown in from high up.
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