Desktop totally dead

[mactoshb]

My desktop suddenly will not switch on, the switch goes in and out with no obvious clicks etc, I am assuming the switch initiates an electrical circuit and not a physical switch movement.
I have a pen type tester that detects power in a cable from about 1cm away and it detects power in the cable at the input to the PSU but detects no power in any area of the M/B nor on any of the twenty or so cables that exit the PSU to plug into the various connectors on the M/B
I would appreciate any advice on whether it is likely to be the switch and if it can be either fixed or replaced.
Thanks Boyd (mactoshb)

 

[johnb35]

Is this a store bought pc such as Dell, HP, Lenovo or a custom built pc? If custom built, you can always short out the power pins on the motherboard to see if it will start up. The motherboard basically tells the psu to turn on when the power button is pressed. Could be bad switch, motherboard, or psu.

 

[mactoshb]

It is a second hand HP compac, bog standard, nothing other than wi-fi dongle and printed connected. I will short out the pins later when I get home and see what happens
Boyd

 

[CP30126]

I have a pen type tester that detects power in a cable from about 1cm away and it detects power in the cable at the input to the PSU but detects no power in any area of the M/B nor on any of the twenty or so cables that exit the PSU to plug into the various connectors on the M/B

What? That's a thing that actually exists? This is the first time that I hear of such a gadget. I'm guessing that the voltages are too low for them to be detected.

 

[mactoshb]

The gadget is a simple tester from B & Q I have attached two photos one with the front cover off, which I do not think is intended to come off but I have found it is much more sensitive with it off and it unfailingly beeps and flashes when in contact with the positive wire in a cable outside the insulation on it, it even starts to beep sometimes when close without contact. I recently sat it on the control box for my heating in a cupboard and it had to be removed onto the shelf as it reacted to the live cable in the controller,
Sorry to have taken so long to respond but I find trying to do these replies on my phone is not as simple as when the Desktop is working OK
Boyd

 

[beers]

That's a thing that actually exists?

EMI 'pens' are pretty common, usually used when you're working on things you aren't sure that are live or not.

Not sure if you'd get the same behavior on a low voltage DC waveform. There's some PSU testers that go into the ATX plug and will measure the voltage on each rail, although they aren't really reliable for measuring load or sag.