Power problem with new upgrade

  R6-Mad 12:27 09 Mar 2005

Hi, This is a strange one - my computer will only boot up if i switch of the power switch on the power supply for about 20 secs and then it's ok.
It's a 450 supply and i have just done an upgrade motherboard is an asus A8V Deluxe and new AMD 3500 skt 939 64bit.
Any ideas would be great

  John-259217 13:55 09 Mar 2005

Is your power supply made by Q-tec by any chance?

I have a system (MSI K8T, Ath64, 6800GT plus a bunch of HDD`s and cards) which behaves in exactly the same fashion. It has a Q-tec 450W supply.

Substituting an old 350W supply removes the problem, similarly connecting the Q-tec to a KT4 Ultra board produces the symptoms on that machine.

Do you have an alternative power supply you could try?

Even a small (250W) one will run the board well enough, if you unplug any unused equipment (CD drives, second HDD`s etc), for test purposes

Its also possible that the case switch may be faulty, it should only work on its two wires, any shorts to the metalwork of the case (trapped wire?) may cause a problem.

Lastly, the mobo may not be calling for power properly from the supply but I think this is

In cases like these substitution of known good components for suspected faulty ones is usually the easiest method of problem solving but I appreciate you may not have spare psu`s, cases, mobo`s etc floating about.

I would suggest waiting for further replies before rushing out spending money on new parts, someone else may have a better solution.

(In my case though it`ll be an Enermax 600W as soon as I get round to it ;-)))


  R6-Mad 15:16 09 Mar 2005

Hi John,
Thanks for the reply !
I will try to change over the power supply tonight when I get home. It's a strange one, even when it doesnt boot up I can still see the power light on the motherboard is green, so i guess that it's still getting power ? When i turn on the power my cpu fan and other cooling fans kick in for a split second until I push the on / off switch and then it's powers up ok. Also somtimes I push the on / off switch it tries to power up again for a split second - (but not always).
Again I have to power off and unplug for about 20secs to get it working again.

All the best

  John-259217 15:54 09 Mar 2005

Mine does the same!

When your psu is plugged into the mains (and any switch on it is turned on) it supplies the motherboard with a signal current. This accounts for the green power light illuminating.

The main switch on your PC is not an on/off switch in the absolute sense, rather it acts as a trigger telling the motherboard to request the psu for power.

This is how the computer can perform Wake On Ring/Lan functions and allow an operating system to power down the machine (its also another reason why you should disconnect the psu from the mains before adding or removing components like ram or PCI cards).

I suspect that the psu`s internal circuitry has capacitors which charge/discharge to allow the power call to occur correctly.

A fault in these or just over-sensitive circuits seems the most likely explanation to me.

My system can take several attempts before it powers up, each time with the brief flash of pwr and hdd lights plus a whirr from the fans.

Probably does it no good whatsoever :-)) oh well more expensive scrap lol.

Good luck


  R6-Mad 16:13 09 Mar 2005

Thanks again John,

So really a new power suppy is required eh :-(


Ok i will try another PSU tonight and see and post in the morning to update you on how i got on.



  R6-Mad 11:36 11 Mar 2005

Tested PSU with another and all work fine - so looks like I will be buying a new one today :-(

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