Hi Folks,
I have a system based on an ASUS Sabertooth X79 and 4930K CPU that has been running fine for several years and was still perfectly adequate for my requirements. I am not a gamer, but edit lots of photos and images. Last Sunday morning I went to switch it on and... nothing! No display, POST beeps, HDD clunks or fans running - nothing. First thought was the fuse in the mains plug, but that is OK and mains is getting to the system.
There had been no prior sign of problems, such as overheating warnings etc. Fine one evening, dead next morning.
So I stripped everything off the motherboard except the CPU and memory, but nothing started except the green LED on the motherboard indicating that power was reaching it. Reset the RTC by putting the link across the header pins for about 30 seconds and removed the button cell for a further minute just to be sure, but still no response to the power switch. I hoped that the button cell had simply expired after running the RTC for years, so I replaced that with a known good cell, but no joy.
I have tested the PSU separate from the motherboard, loaded by a couple of hard drives, using a link between the green Power_On# wire and ground on the 24pin ATX connector, and the PSU fired up with the fan spinning and the drives spun up indicating that they were powered. Checked all the voltages on all of the PSU connectors were within spec using a DVM, including the Power_OK grey wire at 4.75V on the ATX connector.
Re-connected the PSU to the motherboard, but again no response to the power switch - not even the PSU starting up, just the green LED on the motherboard as before. Linked the power switch header pins on the motherboard, thus eliminating the front panel switch, but still no response.
I then tried to force the PSU to start when connected to the motherboard by linking the green Power_On# wire to ground at the back of the connector, however nothing started. I've disconnected PSU and checked it still starts with this link when not plugged in, and also confirmed it won't start when is plugged in, to the motherboard.
Am I right in concluding that the motherboard should be able to pass the power switch through to the PSU without a CPU installed and, if so, my results indicate a faulty motherboard?
Is it likely that the PSU is still faulty, even though it passes the link test under a reasonable load? Obviously only the 5V and 12V supplies are loaded by hard drives, not the other voltages, but they are within specification.
Could a faulty CPU cause these symptoms? If so, how would I diagnose this further? Although the system had no over-temperature warnings before this problem started, I did notice a lot of dust built up in the CPU heatsink when I opened the box up. In the hope that the CPU is still OK, I have cleaned that all out.
Obviously all of this stuff is no longer current, but I'd rather replace the faulty part than do a complete upgrade to a more modern system. Just a question of reliably identifying the faulty part from the tests so far, or any others that can be suggested.
Unfortunately I don't have any other known working parts available, so any help would be appreciated.
I have a system based on an ASUS Sabertooth X79 and 4930K CPU that has been running fine for several years and was still perfectly adequate for my requirements. I am not a gamer, but edit lots of photos and images. Last Sunday morning I went to switch it on and... nothing! No display, POST beeps, HDD clunks or fans running - nothing. First thought was the fuse in the mains plug, but that is OK and mains is getting to the system.
There had been no prior sign of problems, such as overheating warnings etc. Fine one evening, dead next morning.
So I stripped everything off the motherboard except the CPU and memory, but nothing started except the green LED on the motherboard indicating that power was reaching it. Reset the RTC by putting the link across the header pins for about 30 seconds and removed the button cell for a further minute just to be sure, but still no response to the power switch. I hoped that the button cell had simply expired after running the RTC for years, so I replaced that with a known good cell, but no joy.
I have tested the PSU separate from the motherboard, loaded by a couple of hard drives, using a link between the green Power_On# wire and ground on the 24pin ATX connector, and the PSU fired up with the fan spinning and the drives spun up indicating that they were powered. Checked all the voltages on all of the PSU connectors were within spec using a DVM, including the Power_OK grey wire at 4.75V on the ATX connector.
Re-connected the PSU to the motherboard, but again no response to the power switch - not even the PSU starting up, just the green LED on the motherboard as before. Linked the power switch header pins on the motherboard, thus eliminating the front panel switch, but still no response.
I then tried to force the PSU to start when connected to the motherboard by linking the green Power_On# wire to ground at the back of the connector, however nothing started. I've disconnected PSU and checked it still starts with this link when not plugged in, and also confirmed it won't start when is plugged in, to the motherboard.
Am I right in concluding that the motherboard should be able to pass the power switch through to the PSU without a CPU installed and, if so, my results indicate a faulty motherboard?
Is it likely that the PSU is still faulty, even though it passes the link test under a reasonable load? Obviously only the 5V and 12V supplies are loaded by hard drives, not the other voltages, but they are within specification.
Could a faulty CPU cause these symptoms? If so, how would I diagnose this further? Although the system had no over-temperature warnings before this problem started, I did notice a lot of dust built up in the CPU heatsink when I opened the box up. In the hope that the CPU is still OK, I have cleaned that all out.
Obviously all of this stuff is no longer current, but I'd rather replace the faulty part than do a complete upgrade to a more modern system. Just a question of reliably identifying the faulty part from the tests so far, or any others that can be suggested.
Unfortunately I don't have any other known working parts available, so any help would be appreciated.
