Could have been. But it appears that the OP is still having problems.

In reply to a post by 12eason:

In reply to a post by AEP:

I'm not sure that testing a PSU whilst not under load is terribly informative.

It would not be informative if your goal was to measure the voltages, but seeing if it works or not is fine. All PSUs must power on if the green cable is shorted, it's in the ATX spec. They do not have some sort of load detection and auto shut-off feature.

The issue really does point to the motherboard, other component or loose connection somewhere. However I have checked, double checked, removed and then placed back all cables. I have tried out a brand new PSU on the system with all internal connections fitted and I get the same result as with the original PSU - so that seems to eliminate the PSUs in my admittedly non-techy opinion. The fact that the previous PSU, which I did think was the original culprit does in fact power up (under test conditions with no load admittedly) does suggest the fault is elsewhere.

I have checked the power on switch on the top of the tower has not had its wires detached. Given that I hadn't had the slightest problem with the system prior to fitting the new hard drive is the perplexing part.

I have tried to power up with no hard drives connected as well as with just the original three rather than the four now installed. None of which has made any difference. I am just about to try a new cmos battery as suggested by another response. So back to the drawing board

The new PSU presently borrowed and in the machine is an impressive beast - a Nesteq ASM x-Zero 700W - http://www.nesteq.net/gb/products/powersupplies/asm_...

When the power cord is fitted and the switch turned on only the one green light comes on for the 5Vsb not the other three lights.

I don't think you'd need a new battery, just reset the cmos. The worst that will happen if the battery has died is that the computer won't be able to keep time. You'll have to refer the the manual for the motherboard for the correct pins to short to reset the cmos. It's usually a three pin set near to the battery. Obviously, you can remove and reseat the battery too.

Hope it is the cmos, because all the other options are rather more serious. Neither faulty ram or a faulty processor will stop the motherboard powering up and the fans spinning, iirc. So it'd probably be a duff motherboard.

Edited by deleted (Sat 25-Jun-11 17:51:28)

In reply to a post by 12eason:

I don't think you'd need a new battery, just reset the cmos. The worst that will happen if the battery has died is that the computer won't be able to keep time.

Interestingly, I've just had a battle with a non-booting PC. Lights come on, fans rotate, HDD rotates, CD drive rotates, but nothing shown on screen and no POST beeps.
The mobo is ASUS.
I couldn't make any progress until I decided, in desperation, to replace the CMOS battery - when everything burst into life once more.

I was willing to swear it couldn't give the particular symptoms as a result of battery failing, too !!

Edited by dandnsmith (Sun 26-Jun-11 09:44:28)

Does sound odd. I'd have thought the cmos battery was solely used to maintain a clock nowadays. Just assumed all other data was written to flash type memory.

eta: http://en.wikipedia.org/wiki/Nonvolatile_BIOS_memory

Edited by deleted (Sun 26-Jun-11 10:31:52)

In reply to a post by 12eason:

I don't think you'd need a new battery, just reset the cmos. The worst that will happen if the battery has died is that the computer won't be able to keep time. You'll have to refer the the manual for the motherboard for the correct pins to short to reset the cmos. It's usually a three pin set near to the battery. Obviously, you can remove and reseat the battery too.

Hope it is the cmos, because all the other options are rather more serious. Neither faulty ram or a faulty processor will stop the motherboard powering up and the fans spinning, iirc. So it'd probably be a duff motherboard.

Well new battery fitted so apart from resetting the CMOS I have achieved nothing. I am only left with the likelihood of a motherboard that for whatever reason has died on me and the fitting of a new hard-drive was merely coincidental. Goodness knows why the mobo has failed though.

Now need to research a suitable replacement. Oh the joys of computing...... of course SWMBO is not impressed at a week lost when I should be doing other things let alone the cost of it all

I am only left with the likelihood of a motherboard that for whatever reason has died on me and the fitting of a new hard-drive was merely coincidental.

Have you eliminated the short-circuit possibility by trying the motherboard out of the case? It's a very common cause of the sort of problem you describe. You could easily have moved something when you installed the drive. (Or even dropped a screw into the works - it happens!)

If you're thinking in terms of replacing the motherboard then you're going to have to take it out of the case anyway. You might as well try testing it then, even if it's a remote possibility.

In reply to a post by AEP:

I am only left with the likelihood of a motherboard that for whatever reason has died on me and the fitting of a new hard-drive was merely coincidental.

Have you eliminated the short-circuit possibility by trying the motherboard out of the case? It's a very common cause of the sort of problem you describe. You could easily have moved something when you installed the drive. (Or even dropped a screw into the works - it happens!)

If you're thinking in terms of replacing the motherboard then you're going to have to take it out of the case anyway. You might as well try testing it then, even if it's a remote possibility.

Good point - no harm in giving it a try at least. Think it will have to wait until I have done a few outdoor jobs first particularly since it is such a pleasant day and I don't have another mobo to replace anyway. I will let you know if it springs to life. Ever hopeful

This is gonna be mother board and not PSU.

I would take everything off that board and fit one piece at a time and try boot after each one ( including on a empty board) see if it powers up at any time..if not its the mobo

Just to close off this thread. It was indeed the motherboard so have taken the opportunity, after much thought and angst, to upgrade both board and processor.

Thanks to everyone who helped trace the fault eventually.