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Tech Helproom


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PC not powering up


Scubaman

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Hi A friend has had a problem whereby his PC will not power up. With the power on when he tries to power up his PC nothing happens. He has been to Maplins who checked his PSU and told him that one of the feeds was u/s and sold him a new one. After installing the new PSU guess what, exactly the same. Before he turns up on my doorstep tomorrow I was wondering if anyone has any ideas.

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Fruit Bat /\0/\

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  1. does the socket work?

  2. check fuse in plug check plug wiring (if not moulded on)

  3. switches on rear of PSU if fitted make sure set to correct voltage and in on position.

  4. If certain PSU is good: disconnect all drives and see if it powers on to and error massage.

  5. if still dead remove memory and see if it powers on and beeps with error codes (m/board speaker must be fitted or leds on motherboard to give code No.

  6. if still dead then looking like bad motherboard or cpu remove from case lay on paper and retry (checks for shorting to case)

Take PSU back to Maplins and ask for a refund

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onthelimit1

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Could it be the start switch/harness on the Tower? If the PSU won't start when the button is pressed, remove the main 20/24 mobo connector, and connect Pin 15 (green)on the connector from the PSU to any black pin. The PSU fan should spin. If it does, the fault is with the switch, harness or, as FB said, the mobo is kaput.

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Scubaman

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Have checked the PSU and yes it is faulty. If I short out the green wire with any black the fan will pulse once, but if I flash the link the fan will spin ok. I noticed that I am getting 2.7 volts from these two pins, should it not be 12v?

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onthelimit1

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Probably not 12 volts. Scroll down to the diagram in the link and you'll see there are several voltages provided to the mobo and other hardware. The green oin just states 'power on'/

here

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Scubaman

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I replaced the PSU and checked it before installing and the fan did run by connecting pin 14 (green) to the black pin. The PC is still dead, not even the LED's light up or the CPU fan runs. I have disconnected all drives and removed the memory and the graphics card I have noticed that the white cable, pin 18 on the new PSU is missing, in the link you mentioned it showed in the diagram the white cable has been omitted for certain versions. As the old PSU has a white cable, which is connected to pin 8 and not pin 18 - which is a blue cable, could this be the wrong PSU supplied. All very confusing.

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gengiscant

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I had exactly the same problem this morning with my better half's PC,all the signs pointed to a PSU failure so I swapped it,as a PC builder I am fortunate to have spares of virtually any component. Anyway her PC powered up, problem solved. Later I hooked up her PSU to my test bed, lo and behold it worked.

So have not got a clue as yet,when I have the time I shall run a few tests on the PSU.

Dosen't help you I know.

You do not mention what the Mobo is, newer boards tend to have LED's which gives an indication of whether power is reaching various parts of the board and even when the PC is off there is usually a LED the MOBO still on.

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onthelimit1

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The leads from the 'on' switch on the front of the case usually connect to the mobo through small connectors on the front corner of the mobo (opposite side to the PSU). If you Google the mobo number, you should be able to find a mobo diagram that will show which of those connectors are which. Removing the two from the switch and connecting a circuit tester would prove the switch and harness. If all is well, it does sound like a duff mobo.

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Scubaman

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It is a 2003 model PC with a MSI 6534 VER: 1 mobo, and I can't get any joy from Micro Star or find anything on Google. I have checked the power swith and the circuit is ok. There are no LED's on the mobo just the two on the front of the tower. I will tell him the bad news about the mobo. Cheers lads

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