Excuse my rusty english Hi Folks i hope I will find solution to my problem which started when the PSU/750W failed I replaced it with those new ones with 14 mm fan, the CPU fan spin but no post then i used a friend’s one and still no joy .to make the story shot I replaced mobo and memory and changed CPU and graphic card and still no post i took the MOBO out of the case with only cup and a sick of ram and graphic card and still the same the fans spin but no post. The 4 pins cable is plugged in as well as the 24 Molex. know i was examining the old PSU I find it had a white wire and in the new PSU is missing, i looked in the MOBO manual and the white wire (-5 v) is present in the drawing. Now could this be the problem? I’ve ordered one with -5 volt. My system: GA-N650SLI-DS4L, Q6600 2.4, 4GB ram, NVIDIA 8500GT 1024MB

When a PSU goes bad it's not uncommon for it to take the motherboard and/or cpu with it. Are you getting any posting beeps when turning it on? If the new PSU has a 115/230 voltage switch make sure it's in the correct position. You've swapped out everything possible except the motherboard. Assuming the new PSU is good as well as the swapped ram, cpu and video then I'd think the motherboard itself if bad.

Hi there well first thanks for the reply, let's make myself clear first I swapped the PSU with brand new one 750w still getting no post from the computer then I suspished the MOBO so i swapped it with asus P5N-E SL still same issue no post no peeps so i took the MOBO out of the case, and I tried it out of the case only with 1 stick of ram,CHF and graphic card and a speaker plugged to the motherboard. Still no bleep, no POST. I then swapped the graphic card, still the same problem. I swapped the processor with known working one and still nothing. The only thing I figured out is the old PSU has white wire -5v and that computer was working with it fine before it failed, now with this new PSU it has the white wire missing. Is this the problem?

If the new m/b needs the -5 then yes. Not all boards require the -5 so check the manual or look at the connector on the m/b and see if the -5 pin is there or if the socket is empty. Hope this helps

Newer mboards require you connect the main wiring connector from the PS, AND another smaller power connector from the PS to a socket elsewhere on the mboard. If that applies, did you do that? Otherwise... If neither mboard works with the new power supply, the most likely thing is you're trying to use incompatible ram. If you changed the ram before you changed the original PS, there may be nothing wrong with the original PS. "...the old PSU has white wire -5v" I'm assumimg all the other wires in the main connector are the same colors in the same positions - usually that's the case. That white wire is for an ISA bus function. Older ATX PS main wiring connectors have that, newer ones often don't, except sometimes they have it for backward comptibilty with older mboards that do have ISA slots. If your mboard has no ISA slots, you don't need it, there is no circuit on the mboard connected to that position in the mboard socket, and even if it does, ISA slots will work, they just cannot use that function. "...I replaced mobo and memory..." Ram that works in another mboard , or any ram you buy or have lying around, may not work properly, or sometimes, not at all - even if it physically fits and is the right overall type (e.g. SDram, DDR, DDR2, etc.; PCxxxx, xxx mhz) for your mboard. In the worst cases of incompatibilty your mboard WILL NOT BOOT with it installed, and the mboard may not even beep - the ram has to be compatible with the mboard and it's chipset. See response 5 in this for some info about ram compatibilty, and some places where you can find out what will work in your mboard for sure: http://www.computing.net/hardware/w... Correction to that: Mushkin www.mushkin.com Once you know which module ID strings work in your mboard, you can get them from anywhere you like that has ram with those ID strings. If you have brand name ram, it is usually easy to look up whether it's ID string is in a list of compatible modules found by using your mboard or brandname system model number. If the ram is generic, that may be difficult or impossible. ... It is easy to test for whether incompatible ram has caused your mboard to fail to boot, or it's caused by another problem. Make sure you have a speaker or speakers connected to the mboard so you can hear mboard beeps (see your mboard manual). Remove the AC power to the case/power supply. Remove all the ram. Restore AC power. Try to boot. If nothing else is wrong, you will hear a pattern of beeps that indicate no ram is installed, or a ram problem. E.g. for an Award bios or a bios based on one, that's often a beep of about a half second, silence for a half second, a beep of about a half second, silence for a half second, continuously.

I missed that you'd replaced the motherboard too. Was it new or known to be good? In the same way a bad PSU can take out a motherboard, it's also possible for a bad motherboard to ruin a PSU, although that's not usually the way it happens. If the problem originated with the motherboard then maybe the new PSU is now bad. Again, that doesn't seem likely but given your circumstances you may want to try a third PSU.

yes the memory are compatible with the mobo they're DDR2 800 pc6400 and are working when i remove all the memory sticks and start the computer i hear all the fans working but no peeps from the speakers and that indicate the mobo is faulty i think. ipurchased a new mobo asus P5N-E SL i plugged the 24 pins plug in and the 4 pins plug as well and this time none of the fan spins and no peep but ther is a greene light in the mobo ,may be is faulty i spoke the shop and he told to send it back for replacement,could some one tell me if he knows how to get a wire carring -5v to replacxe the missing wire just to try it and this what it says on the mobo where the PSU 24 plugs goes ,does not say -5v optional Pin No. Definition Pin No. Definition 1 3.3V 13 3.3V 2 3.3V 14 -12V 3 GND 15 GND 4 +5V 16 PS_ON(soft On/Off) 5 GND 17 GND 6 +5V 18 GND 7 GND 19 GND 8 Power Good 20 -5V 9 5V SB(stand by +5V) 21 +5V 10 +12V 22 +5V 11 +12V (Only for 2x12 pin ATX) 23 +5V (Only for 2x12 pin ATX) 12 3.3V (Only for 2x12 pin ATX) 24 GND (Only for 2x12 pin ATX)