I am trying to fix this board (3 years old) which cannot boot. While measuring voltage at various points, I encountered another problem.
Original problem first. If I leave it untouched for a few days, it boot for 3-4 sec, the 2-digit LED lighted up and changing values, then it went off and only the CPU fan and chasis fan turning, nothing else works. If then I shut it down and restart the power again, only the fans turn and LED never light up.
After studying for months, I now can figure out the VRMs and most of the large components on the board. So I check the connectivity without the power. For components that I can identify their pinouts, they look good. Then I power it up and measure the actual voltage of the points I know. Chips Vcc seems ok. Power MOSFET has their reasonable difference between D & S. Vtt is 1.05V. VRM for CPU display (i7 2600K) is only 0.91V which I don't know if it's ok or not. When I measure Vcore I got 0V, input to VRM all 12V. But then only when I saw the psu fan stopped I realize there was no power to the board.
Here comes the second problem. I then tried to power it up again, but it never would. Even the fans didn't turn any more. Pressing the power button just trigger nothing. Checked the +5VSB on ATX power plug is 5.01V. The SIO chip (NCT6776F) also has its 3.3V SB.
I don't know how to proceed further. But I know I have to solve the second problem first before resuming the frist problem. Can anyone help me?
Original problem first. If I leave it untouched for a few days, it boot for 3-4 sec, the 2-digit LED lighted up and changing values, then it went off and only the CPU fan and chasis fan turning, nothing else works. If then I shut it down and restart the power again, only the fans turn and LED never light up.
After studying for months, I now can figure out the VRMs and most of the large components on the board. So I check the connectivity without the power. For components that I can identify their pinouts, they look good. Then I power it up and measure the actual voltage of the points I know. Chips Vcc seems ok. Power MOSFET has their reasonable difference between D & S. Vtt is 1.05V. VRM for CPU display (i7 2600K) is only 0.91V which I don't know if it's ok or not. When I measure Vcore I got 0V, input to VRM all 12V. But then only when I saw the psu fan stopped I realize there was no power to the board.
Here comes the second problem. I then tried to power it up again, but it never would. Even the fans didn't turn any more. Pressing the power button just trigger nothing. Checked the +5VSB on ATX power plug is 5.01V. The SIO chip (NCT6776F) also has its 3.3V SB.
I don't know how to proceed further. But I know I have to solve the second problem first before resuming the frist problem. Can anyone help me?
Comment