I built this PC about 2 months ago, other than a few minor issues, the system worked fine until yesterday. The system just die out of a sudden as if someone just turn off the power supply.
Now, when I press the start button - all fans (on processor, case, PS) spin for a split of second and stop. ( The LEDs too will go on and off during that time) Subsequent pressing on start button produce nothing. Only after turning power off by flipping switch on PS or unplugging the cord from electrical outlet and plugging it back makes it possible to try to turn it on again. But then again... all fans (on processor, case, PS) spin for a second and stop...there were no video input on the monitor(s).
I also noticed that the system behaves differently if I remove the ATX(12V, 2x4)) connector. All the fans and leds will continue to run/lit, but there is no video signal. During this time, 12V is measured on the ATX connector . (Wondering whether there is a way for me to check whether the 12v circuitry on the motherboard is shorted..?)
I have replaced the power supply with a brand new Thermaltake 750W PS .. unfortunately, the result is the same.
I would appreciate if you have any clues that I can use. Thank you all in advance!!!
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 think I have isolated the problem to the motherboard... can someone comfirm for me my analysis is correct and can tell me what component on the motherboard you think has failed.
With only the power supply and motherboard (no CPU, no video card and no memory installed.), the system behave pretty the same.
1. With the 12V ATX connector installed, the board/system led/fan will try to start up but failed/quite after a split of a second.
2. After I removed the ATX connector, the board/system led/fan will stay on until I turn off the power supply.
1. Does this confirm the failure is on the motherboard?
2. Is it correct to conclude that a 12V device on the motherboard is shorted and the power supply simply tripped?
3. What device(s) on the motherboard uses 12V?
PS: I am trying to avoid RMA'ing the wrong parts. Thanks.
The problem was isolated to the motherboard. I replaced the motherboard and system work fine until this morning. The system is exhibiting the exactly same symptom. Looks like the MSI 790FX-GD70 is is piece of junk!