BODS 07:28 12 Aug 04

HI, on starting my old pc found it starts-up one day then the next it will not.
left it for few days and did the same as above but now it will not run at all. have checked normal power items but no power to pc ,is the psu finished .win95b atx board psu 250watts
can anyone help.bods

  cga 07:47 12 Aug 04

I don't know how you checked the power output of this but, remember, an atx psu is relay switching. This means that it will ony output power on cetaintain connecters until the mobo switches in the rest.

If you have not checked the mobo outputs then it could be either the psu or the mobo.

  Gongoozler 07:54 12 Aug 04

As cga says, it's very difficult to be certain whether the fault is in the power supply or the motherboard. It is possible, but with a power supply being available for under £6, I think substitution is the easiest way click here

  GRFT 08:14 12 Aug 04

You only need to have the PSU/MoBo 20-pin connector in place (plus the 2-pin cable from the the front panel on/off button. Disconnect all other ribbon and power connectors. If the PSU doesn't then switch on then it's almost certainly faulty. As mentioned, substitution is the best way. Tha's why I always have a cheapo PSU, among other bits, for problems like this.

  cga 08:22 12 Aug 04

Correct me if I am wrong but, if the mobo really is dead then it will not switch in the psu relays, will it? Or is this such a basic mobo function that it never dies?

  Gongoozler 08:30 12 Aug 04

Hi cga. A failing motherboard is just as likely to cause this problem as a failing power supply, but the power supply is easier to change, and much cheaper. The power switch is also a possible cause. The way to check this is to find the two pins on the motherboard that the switch connects to, and momentariliy short them together.

  cga 08:43 12 Aug 04

No problems with your recommendation at all. A 250w psu may be a bit small anyway depending on what is in the box.

  GRFT 08:05 14 Aug 04

Yes, as already mentioned, a faulty MoBo could cause the PSU not to switch on. The ON button sends a ground signal to the PSU via pin 14 (PS_On) of the PSU connector. Then at switch on, if all output voltages are correct then Power_OK on pin 8 goes low. Otherwise the PSU remains off.

  GRFT 08:34 14 Aug 04

For a description of ATX power supplies click here

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