Hello, I just brought a new system and it don't have display even if there is light on the motherboard and all(cpu cooler, gpu and case fans) fans are spinning for 1-2 seconds. Then the system power off and power on for 1-2 seconds. And then it power off. How can I know if it is the problem of the motherboard or of the cpu? Do I have to buy a motherboard speaker?
Thank you in advance
Did you buy a new system or parts for a new system?
If a new assembled system, did it came with a warranty? If so, let the seller fix it like he's supposed to.
Next please list the system specs.
Work through our standard checklist and troubleshooting thread: http://www.tomshardware.com/forum/261145-31-read-postin... I mean work through, not just read over it. For example, Step 3 pretty much requires removing the motherboard to check. and if you are going to do that, you may as well breadboard the system. Did you do this?
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU. You do have a case speaker installed, right? If not, you really, really need one. If your case or motherboard didn't come with a system speaker, you can buy one here: http://www.cwc-group.com/casp.html
Step 16 mentions the system speaker and why you need it. And you are asking if you need to buy one?
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. (This is why you need a case speaker.)
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:
At this point, you can sort of check the PSU. Try to borrow a known good PSU. 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.
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 or long single beeps indicate a problem with the memory.
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.
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.