Desktop won't turn on - tested PSU

April 6, 2011 at 19:20:16
Specs: Windows XP
This system is about 4 years old.

Specs from Newegg:
PSU: XCLIO GOODPOWER 500W 500W ATX SLI Certified CrossFire Ready Active PFC Power Supply
CPU: AMD Athlon 64 X2 3600+ Brisbane 1.9GHz
RAM: G.SKILL 1GB (2 x 512MB) 240-Pin DDR2 SDRAM DDR2 800 (PC2 6400)
Motherboard: BIOSTAR TFORCE 550 AM2 NVIDIA nForce 550
GPU: EVGA 256-P2-N624-AR GeForce 7900GS 256MB 256-bit GDDR3 PCI Express x16 SLI Support

System shut off on its own a few days ago. Light on the back of the PSU blinks when the power is plugged into the motherboard, but is solid when hooked up to my PSU tester. Voltages all within normal ranges on the PSU tester. Tried a new motherboard (BIOSTAR TA790XE AM2+/AM3 AMD 790X - I know, AM2 processor in AM2+ board, but it's supposed to be fine) today - same issue: a blinking light on the PSU, no power to the system (no lights, no beeps, nothing). Put my old motherboard back in, ensuring everything was tight and such - still no dice. Tried without RAM, tried with the sticks in every possible configuration - still nothing. CPU still has a good amount of Arctic Silver on it, but I didn't see what the temp reading was right before the system crashed.

Not sure what the issue could be here. Could the PSU test normal with my tester, but still be shot? It appears that the motherboard isn't the issue, so the only things I can think of are:
1. CPU dead
2. RAM dead
3. PSU dead

Would appreciate any help here, as I'm completely stumped and don't want to start shelling out cash for components I may not need...

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April 7, 2011 at 09:52:16
"Voltages all within normal ranges on the PSU tester"

That's all well & good, but what about amperages? Can the +12v provide 18A if required, or is it only capable of 5A? In other words, it's still very possible that the problem is due to a bad PSU.

"CPU still has a good amount of Arctic Silver on it"

The paste application for AMD CPUs is the "middle dot" method. All that's needed is a tiny dab in the center of the CPU, then the heatsink is installed over it. The paste is NOT supposed to be spread around like frosting on a cake. Here's what is should look like before the heatsink is installed:

Not like this:

If you're not hearing any beeps at startup, especially when no RAM is installed, the problem would have to be with the PSU, CPU or motherboard. Since you tried a different board & had the same problem, that should rule out the board, leaving the the PSU or CPU.

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April 7, 2011 at 17:31:52
A clear misunderstanding of electrical physics led me down the road to thinking it was something than my original inclination (the PSU). I was under the impression that using a PSU tester, which showed the voltages were fine, meant that the power supply was good - clearly not the case, as replacing the PSU fixed the problem.

Thanks a lot for the reply.

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