My computer (which was previously working fine) today simply turned off and started power-cycling. Then after an attempt at a hard reboot, it simply won't turn on at all. No lights on the mobo, no fan spin, nothing.
How do I diagnose this? Could it be anything other than a busted PSU (could a fried mobo, anything else, cause this?)
I have a Corsair TX750, so it's not a cheap power supply.
Please help! This is my production machine, I'm helpless without it.
I can think of one thing, the power cable of the TX750, try another power cable.
If you've got an ASUS mobo then the motherboard LED tells you if the mobo is getting power, if its getting power and not booting, then try reboarding (removing the motherboard from the Chassis, removing components and putting them back, yes processor too if possible, but not compulsory. Put the motherboard on a piece of cloth for 15minutes, then put everything back and try again).
To diagnose the PSU, simply see some websites where they demonstrate how to use another PSU lying around, try running some fans with it to see if its working, but I doubt the PSU is the problem
Let me put the points on the table,even if the processor or anything else was dead, the fans would start running, and therefore we'd know the motherboard is alright something else is wrong, so in theory its safe to assume for the moment that the motherboard isn't recieving any power, OR the power button's cable of the chassis which goes to the front panel on the motherboard could be damaged, so joining those 2 pins might just do the trick. (I never tried it, someone else 'jumped' it with a minus screwdriver)
It helps to have a few spare parts or a friend who does so you can replace these parts to help identify the problem part.
usefull spares:- PSU, simple graphics card (even PCI if PC has a PCI slot).
A high power graphics card needing a 6 or 8 way 12V supply can be replaced by a simple graphics card and a low power PSU
I have seen the rebooting shutdown cycle caused by corrupt bios (where there was no jumper to force second bios to take over)
If starting PSU with paper clip have you used a volt meter to check 5V & 12V and 3.3V levels.
If a Intel CPU the 12V 4 or 8 way connector must make a good connection.
I saw a burnt 12V connection on a Dell PC preventing booting.
(I cleaned up motherboard pins and soldered on a replacement 12V connector to the cable from the PSU which cured the problem)
Also look at the capacitors on the motherboard near the CPU for signs of leaking/bulging
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.
Make sure you plug the CPU power cable in. The system will not boot without it.
I always breadboard a new build. It takes only a few minutes, and you know you are putting good parts in the case once you are finished.
You can turn on the PC by momentarily shorting the two pins that the case power switch goes to. You should hear a series of long, single beeps indicating memory problems. Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU. Remember, at this time, you do not have a graphics card installed so the load on your PSU will be reduced.
If no beeps: Running fans and drives and motherboard LED's do not necessarily indicate a good PSU. In the absence of a single short beep, they also do not indicate that the system is booting.
At this point, you can sort of check the 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.
A way that might be easier is to use the main power plug. Working from the back of the plug where the wires come out, use a bare paperclip to short between the green wire and one of the neighboring black wires. That will do the same thing with an installed PSU. It is also an easy way to bypass a questionable case power switch.
This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU.
If the system beeps:
If it looks like the PSU is good, install a memory stick. Boot. Beep pattern should change to one long and several short beeps indicating a missing graphics card.
Silence, long single beeps, or series of short beeps indicate a problem with the memory. If you get short beeps verify that the memory is in the appropriate motherboard slots.
Insert the video card and connect any necessary PCIe power connectors. Boot. At this point, the system should POST successfully (a single short beep). Notice that you do not need keyboard, mouse, monitor, or drives to successfully POST. At this point, if the system doesn't work, it's either the video card or an inadequate PSU. Or rarely - the motherboard's PCIe interface.
Now start connecting the rest of the devices starting with the monitor, then keyboard and mouse, then the rest of the devices, testing after each step. It's possible that you can pass the POST with a defective video card. The POST routines can only check the video interface. It cannot check the internal parts of the video card.
i had the same psu / problem. My PC just wouldn't turn on one day. The power supply somehow surged the mobo. If you check the psu with the pins jumpered (or an led test plug) everything will seem ok but it has totalled the mobo already. I sent my mobo back to asus on warranty and bought a new power supply. One of these days i will get around to shipping corsair the psu back (5 year warranty) I just turned up this thread on a google search to see if anyone had had the same psu/ problem. When i took the psu to canada computers they said it was fine (because they are morons and never hooked it up to a motherboard like i asked them to) Check your mobo for very slightly burned traces to see if you have the same problem as me. Pretty sure that's it. Whatever you do don't hook any replacement mobos to that power supply, as they will generate magic smoke instantly.
Well, I test benched my PC, carefully adding components, and I'm managed to isolate the problems (2). And it's very weird.
1) Whenever the front panel header USB is in use, the mobo will not power on AT ALL. If it's not plugged in, the mobo powers on and boots fine.
2) When my drives are plugged into SATA ports 1 and 2, the mobo gets stuck at the BIOS splash screen, and the splash screen has a garbled top half. If I use SATA ports 3 and 4, it boots fine.
Let me just go ahead and say this.
What. The. ***.
I've never seen anything like this. This is definitely what's happening, I tried it with a hundred different permutations, it is definitely the USB and SATA.
So, my machine is functional as long as I don't plug anything into the USB front panel header, or SATA ports 1 and 2.
Any ideas why this might be? Almost definitely a motherboard issue, so I went ahead and filed for an RMA with Gigabyte... but I'm not sure why this happened. I should mention that all this started after I plugged in a cheap chinese bluetooth dongle into my front panel USB port... but I can't imagine that a Bluetooth dongle somehow fried part of my motherboard...