PSU problem

Hopefully this is the correct forum to use for my query.

On Monday I added a further hard-drive to my home built (PCPro spec) PC. On putting everything back together I go to switch on and nothing. Just the slightest hint of a couple of fans moving momentarily but certainly no more than a few millimetres. Now as the PSU is only 3 years old it seems unlikely it has packed up already and has never previously been an issue. So what else might be the cause? Any thoughts anyone.

Does it still work if you take the new drive out?

If so it could be that the higher start-up surge with an extra drive is tripping the crowbar protection circuitry in the power supply.

Disconnect drives. Be sure to check if the PSU and CPU fans are turning on startup.

In reply to a post by billford:

Does it still work if you take the new drive out?

If so it could be that the higher start-up surge with an extra drive is tripping the crowbar protection circuitry in the power supply.

Bill - it makes no difference. I now have the sides off and nothing else plugged into the back so it is only the internal bits of kit that are drawing power and more importantly can see exactly what does or does not happen when I press the on switch. The CPU fan and several other fans make an attempt at starting but merely twitch the once. A small blue light by the side of the one switch flickers for the merest of time. So I am still perplexed.

Sod's law says that my son has just rang from Gran Canaria and wants a copy of something on one of the hard drives!

In reply to a post by camieabz:

Disconnect drives. Be sure to check if the PSU and CPU fans are turning on startup.

Disconnected all four drives - the previous 3 and the new one and it makes no difference at all. The CPU fan and several other fans in the tower have a momentary attempt at moving but do nothing other than twitch.

Have you checked all of the power connectors, particularly the main one to the m/b, to make sure they are fully plugged in? It sounds to me as if you might have disloged one of the connectors slightly.

In reply to a post by AEP:

Have you checked all of the power connectors, particularly the main one to the m/b, to make sure they are fully plugged in? It sounds to me as if you might have disloged one of the connectors slightly.

Thanks AEP, I did do a quick check last night but it was getting late so I think I will systematically go through and check all connections to the motherboard and also where two cables get connected to each other. It may be that I dislodged something somewhere along the line.

Hopefully that will do the trick as there hasn't been the slightest hint of a problem from the PSU - it is a Zalman ZM600-HP Heatpipe Cooled 600W Modular PSU purchased in April 2008 and from memory I built the PC in late May early June 2008 by the time I had all the necessary parts. It is not my main machine as I mainly use my iMac My son did use it for his course work and his business when he lived here.

I would test the PSU in isolation, to rule out the motherboard. Unplug all the cables including the two motherboard ones. Get the 20/24 pin main motherboard cable, bridge pins 13 and 14, 14 is what tells the PSU to switch on, 13 is just ground (you can use any black wire). It's an easy wire to spot as it is the only green one and it's right next to the clip. Pinout; http://pinouts.ru/Power/atxpower_pinout.shtml
Once you've bridged it, turn the PSU on and either the PSU fan will spin up or it won't. If it doesn't it's knackered, but even if it does, it could be that the PSU is putting out low voltage on one or more of its rails, but that is pretty rare tbh. Usually they just go completely in my experience. You'd need another PSU or a multimeter to go any further.

Edited by deleted (Wed 22-Jun-11 20:10:11)

I used to see some psu's behave like this after a dirty shutdown,
one trick was to unplug the whole machine overnight, and magically it worked in the morning.

Thanks - but the issue is now 3 days old so has been switched off since Sunday, which is when I started on this 'quick' task! No change since then. Looks like I may need to dig out my paper work to check the warranty period or buy a new PSU. Not sure whether it has 2,3 or 5 year warranty. Knowing my luck it will be 3 years and just outside! If it turns out not to be faulty but is a motherboard issue at least I would have a spare PSU. You have to look on the bright side somehow.