flashing power LED on Intel DQ45QB

I have a PC with Intel DQ45CB mainboard. It was working in the office.
I brought it home, and when I connected it to power socket, power LED
flashes about once a second. If I press front panel power button,
nothing happens: no beeps, no fans move.
The green LED on the board meaning standby power is lit. There is
another onboard LED for AMT function and that is off.
I downloaded the documentation for this board, and there is no mention
of this. Some boards blink the power LED in sleep state, but this
board is designed to use dual-color LEDs to indicate sleep.
I wondered if it were some obscure diagnostic meaning some power rail
is down. I swapped the power supply but it still just flashes.
I unplugged the SATA drives, and removed RAM and PCI cards - still the same.
Any idea what this is?

wrote:
I have a PC with Intel DQ45CB mainboard. It was working in the office.
I brought it home, and when I connected it to power socket, power LED
flashes about once a second. If I press front panel power button,
nothing happens: no beeps, no fans move.
The green LED on the board meaning standby power is lit. There is
another onboard LED for AMT function and that is off.
I downloaded the documentation for this board, and there is no mention
of this. Some boards blink the power LED in sleep state, but this
board is designed to use dual-color LEDs to indicate sleep.
I wondered if it were some obscure diagnostic meaning some power rail
is down. I swapped the power supply but it still just flashes.
I unplugged the SATA drives, and removed RAM and PCI cards - still the same.
Any idea what this is?

Double check the main 24 pin power is seated.

And that the ATX 12V 2x2 square connector (two yellow wires, two black wires)
is connected fully to its connector.

*******

Since the system has AMT, I'll take a guess that the motherboard wishes
you to connect the LAN connector to any working Ethernet device. You
could, for example, connect it to your router. When that happens, the
NIC will negotiate a networking rate, and the LAN interface will "come up".
It could be, that AMT seeks to have a working LAN connection, before it
will let the computer start or something. This is just a guess on my part.
I have no AMT experience at all.

*******

I don't really know what the AMT status LED means.

AMT is a small processor inside the chipset. It uses a portion of
system memory for computations. The BIOS chip has code for both AMT and
for the system processor. But what functions are in the AMT code, or
what configuration information it is currently running on, I haven't
a clue how that works. Intel provides software to talk to AMT, but
that's going to be useless if you cannot get the system to start.

In terms of potential diagnostic information.

1) Plug in the LAN connector. Look for the LEDs to light up.
If the LEDs will not light up, either there is no Power_Good
coming from the power supply, or the board is "jammed in Reset".
That is the indication I used in the lab, for boards not coming out
of reset, was a failure to negotiate a rate with the LAN (no LEDs would
light as long as Reset is pressed). Even with no CPU plugged into
the PCB, the LEDs should still light if things are working (Ethernet
PHY has power).

2) You can do a "no memory" test, as a test that power is available.
Power off the computer completely, and unplug it. Remove the memory
DIMMs, using anti-static precautions. Store the DIMMs in their
anti-static container. Now, connect power to the computer and power
on. You should hear a three-beep repeating pattern. Hearing the pattern
tells you: The system has power, the BIOS is working, the motherboard
chipset is in good shape. It cannot tell you every chip is healthy, but
the core of the system is working. If you hear no beep codes at all,
then "the system is sick". Hearing the two or three beep pattern, is
a good result.

Power down the system, unplug the power cord. Put the DIMMs back, using
a wrist strap as a means of anti-static protection. The wrist strap
brings the DIMMs and motherboard to the same potential, slowly. Now,
you can plug the power back in again.

Never service the DIMMs while the green LED is lit. All LEDs must be
"off" before removing or adding DIMMs! It can take up to 30 seconds
for the green LED to "drain".

3) The motherboard has POST codes. You would need a POST card to
display the codes. A POST card costs $20 to $100, depending on whether
it comes directly from Hong Kong or not.

The POST card will stay at 0x00 or 0xFF, if the system is not powered
properly (ATX12V not plugged in). Or, if the CPU is bad. Some POST cards
have a LED for each power rail, to show if some power is missing.

The Intel document DQ45CB_TechProdSpec.pdf has a table of POST codes
for usage with your POST display card. The POST codes are
"progress codes" and they tell you the last thing the motherboard
tried to do. Unfortunately, they are not "error codes", and the
motherboard will not try to tell you in a plain language what the
problem is. This is the big problem with POST codes, is all of the
interpretation of the results, is left for the operator to guess at.

If you happen to already own a PCI Port 80 Post Display card, you
can use it. But if you don't own one, it generally is not worth
investing money in one. Port 80 codes seldom add much diagnostic
information, which is why it's better to just borrow a Port 80 Display
than to buy one. If you bought one, you'd be disappointed if it did
not tell you immediately what was wrong. Which is why I can't recommend
buying your own. But if you can borrow one, it's better than nothing.

HTH,
Paul