new power supply - computer starts briefly

  smrdo 09:42 09 Feb 2007
Locked

I've installed a new Antec neo he550W power supply. However when i power on now the machine starts all the fans spin etc for about 5 seconds then it powers down.
All appears to be connected properly, 20 pin atx power & 4 pin cpu (the psu also has an 8 pin cpu cable)

I then have to pull the power cord to be able to repeat this.

motherboard: foxconn 661FX/648FX4MR-ES
1gb ram
2 hard drives
terratek dmx fire 24/96 sound card

graphics: ati radeon 9200se 28mb, this is an old card about to be replaced by a geoforce 7600GS 256mb agp (which is the reason for the new psu) however thought i'd get the psu going first.

  Fruit Bat /\0/\ 09:45 09 Feb 2007

Certainly sonds like a bad PSU, try remaking all the connections.

  Totally-braindead 09:46 09 Feb 2007

Is this a new build you have built yourself or an existing computer that you have replaced the power supply on.
Reason I ask is one of the most common faults for causing a PC to shut down this quickly is an overheating processor. It shuts down to protect itself.
I would look at the heatsink and fan on the CPU first.

  smrdo 09:54 09 Feb 2007

it's an existing comp that i've replaced the psu on, it powered up with the old 300w generic psu, into vga mode as i'd unistalled the old ati drivers in readyness for the new graphics card

  Fruit Bat /\0/\ 10:06 09 Feb 2007

retry with old PSU to prove new PSU is /is not fault.

  smrdo 10:11 09 Feb 2007

would it be agood guess to presume the new psu is faulty if everything powers on and boots with the old one...iwas concerned that it could be a motherboard fault or something. I'll check it out tonight.
One more thing i forgot was that if i removeed the 4pin psu connecter, everything powers on & remians on, obviously nothing happens on screen and the machine cant be switched off unless by turning the psu off.

  Fruit Bat /\0/\ 10:24 09 Feb 2007

would it be agood guess to presume the new psu is faulty if everything powers on and boots with the old one

Yes

if i removeed the 4pin psu connecter, everything powers on & remians on,

have you disturbed the CPU? if not then still mostlikely to be faulty PSU.

  smrdo 10:26 09 Feb 2007

no i havent touched the CPU, made sure i was as careful as can be. anyway cheers for the help, i'll re try the old psu tonight...

  smrdo 09:55 12 Feb 2007

Well tested the old psu on the weekend and all booted up ok, everything worked!!
puit the new one in and connected things up one by one, from a bare mininimum (it got the Windows XP splash then restarted constantly) as I connected eaxh other component the time to shut down reduced, until finally everything connected it shut down after a few seconds.
The PSU's going back for a replacement today!!

  smrdo 09:42 13 Feb 2007

wehey, replaced the psu and all is getting better.
I cant set the optimum resolution on my monitor now though , its a Samtron p94v and i usually run it at 1280 * 1024 @ 60Hz, it wont display this now...anyway, i guess i'll have to live with this until i can afford a new monitor....thansk for all your help

  the old man 10:17 13 Feb 2007

What psu you now got connected.

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