Intermittent PSU start-up problem

  BorderCollie 12:45 28 Jul 2010

I have a Packard Bell "Imedia 3043" desk-top, running XP Pro, using the original psu which is a "FSB Group Inc", FSP 280-60PNA-1(PF) 280w.

For the past 3 months, it has been 'pot-luck' if the pc will start-up or not,by pressing the front panel's trigger switch. Last night, it started and ran for 4 hours with no problem, but immediately after shutting down, it refused to restart again.

When it IS running, if I use the "Restart" option on Win XP Pro, it will shut-down and then auto-restart, but if you "Turn Off Computer" completely, that's it- it won't come on again.

Tried all the usual psu tests- shorting the trigger switch, unplugging the leads,paper clip between green/black with a 12v load, etc, but all won't work. Then leave the pc with the mains lead unplugged for a few days, try it again, and it comes on, but only for that one time- switch it off, it won't switch on again.

Strangely, even when it won't switch on, I still get the 5v dc output from both the front panel usb sockets, which allows me to charge up my sat-nav!!

The cooler fan is free from dust and blockages and works, the psu runs pretty cool when it is operating, there is no smell of burning or over-heating, in fact, when it DOES work, it is perfect.

I've been using exactly the same peripherals since new, the pc has had no modifications or upgrades since new (except for a rail wifi adapter card added 2 years ago)and all the internal connectors, wires and components have been checked as being in place.

Anyone any ideas? Is it likely to be a fault with the psu itself, if so, should I just replace it?

Or could it be an intermittent fault or short-circuit caused by another internal component, or even the motherboard?

I'm totally stumped so any ideas would be most welcome...

Dave Grieve, Dumfries, Scotland

  gengiscant 12:52 28 Jul 2010

I would think the simplest thing would be to replace the PSU rather than faff about with what is rather under powered by todays standards.

  mooly 13:01 28 Jul 2010

If ! the PSU is at fault, then problem is almost certainly a dried out capacitor in the PSU, which are responsible for 95% of failures on any SMPS (switch mode power supply) be it PC, TV, DVD etc.

I agree your best and probably cheapest option is just to replace the whole thing. Although the cost of parts is peanuts I wouldn't advise you working on it as many sections are not mains isolated.

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