System will not boot with no video. green led on and power switch turns psu on and off but nothing else. Have changed CPU Memory and PSU with no success. Also cpu does not even get warm. what is the problem

The flickering green LED on the motherboard is illuminated by the standby power supply, a small completely independent, always on, 5 volt power supply labeled 5VSB usually, output is on the violet wire.

Here's some more detailed instructions about how to check a PSU.

Try to borrow a known good PSU of around 550 - 600 watts. That will power just about any system with a single GPU. If you cannot do that, use a DMM to measure the voltages. Measure between the colored wires and either chassis ground or the black wires. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. Tolerances are +/- 5% except for the -12 volts which is +/- 10%.

The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

If your PSU give wrong voltage it produce same problem with 2 solution:
1-test your PSU
put a wire between green and black and voltage must be:
yellow 12V, red/purple/gray 5V, orange 3.3V.
If your PSU give under voltage (more than -10%):Buy a new one and test your motherboard(mb) with it (in this case there aren't a lot of chance that your mb and/or your CPU are dead)
If your PSU give good voltage:(-10% / +5%):There are a lot of chance that is you mb or CPU
If your PSU give over voltage:Buy a new one and test your motherboard with it (in this case there are a lot of chance that your mb or/and your CPU are dead)

Hi , I suggest try testing single memory modules , one at a time to isolate a faulty module if that is the issue
Another idea is running a Linux live distro os like Ubuntu from bootable disk or flash drive in live/try mode which run from a virtual partition on the ram memory
If Linux runs ok - then likely a Windows related driver / software issue but if same crash issues are observed then most likely a hardware device issue ie faulty memory module , but as varies when crashes i am thinking more the psu - high boot current load demands due to twin SCSI drives , video card etc - old psu - after a few years the power current rating reduces I recall -25% typical , discrete components not so resistant to heat - try to test with a known good high performance psu or just replace , at release date 2002 definitely due for a replacement new psu

check if the cpu fan its working fine, maybe is damaged o dirty, you clean up with an air compress can

if still doesnt works you can try to replace the fan and see if it works

if you have change already the motherboard, cpu and psu here is what you need to do to check your pc by yourself and may be figure out what the cause of the problem.

1. connect the connector on your psu the motherboard. connect psu connector for hard drive, cdrom drive exhaust fan.
2. turn on the pc. look inside, if you see the led on the motherboard turn green then there's a power coming out from the psu.
3. hear the hard drive if its working, you can feel it vibrate.
4. check the little blower in the video card, if its spinning then there is supply in it.

when you turn on your pc the logo on the screen on the monitor will display. should you not see it, check if the monitor is plug in the ac outlet or the extension of your computer. if you see it then monitor is good. If this display followed by a dark screen with no signal display, then it means it is receiving no signal from your video card. go check the vga cable if its properly fix to the monitor and the video card. you can also detach the video card from the motherboard and reseat it properly. this sometime is the fix for no display.

If after booting after the logo, nothing else but dark screen, then is suggest you loosen the harddrive and reseat the connector properly, restart the system again. you can also check if the voltage from the power supply is dropping when there is a load in it. using a multitester test the 4pin connector. readings from the red wireshould be +5vdc and the yellow +12vdc. If its dropping then system will hang. check if there is shorted in your cpu, most of the time it is the blower or exhaust fan.

post back your findings so i can still help you out.
goodluck

he power cable on your psu and the plug to the ac outlet. turn

> PC had been suddenly powering off several times intermittently for a few days leading up to this state. Does this mean the PSU or Motherboard is at fault?

Yes, either CPU or PSU or motherboard are the likeliest culprits.

It's easier to try a different PSU than to try a different CPU or motherboard.

hello, I have a solution for u i think it may help for u.
your problem is:

When u press the start button... the power LED comes on but there is no POST beep or BIOS screen or boot up. The SMPS fan and Processor fans also dont come on at all. there is a small LED next to the SMPS plug on the motherboard that does light up when the system is connected to a power source.
Part of the system configuration is the kind of PSU you have in your system.
SOLUTION IS
So, what kind of PSU?

Try to borrow a known good PSU. Or better yet, see if you can test your PSU in another working system. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead.

try to remove the memory and put it back again make sure put it fit and correctly

You should clarify this a bit more, but please make sure all of your fans are plugged in and the no jumpers are set to over-clock the processor.Also, double check that everything is fundamentally compatible.

When a power supply goes out the way yours did, it's going to fry the MB 99% of the time. So you're going to need a new MB. It's possible that you CPU is ok, but that could also go too. I would replace the MB first, then the CPU if that doesn't work.