Agilent ENA E5071B repair help: Replaced motherboard, turns on and then off

[spicytofu]

The unit only had a bad motherboard, which I replaced. Installed windows xp and all the drivers (CHIPS video and agilent control board). I did all this without powering up the E5071 by bypassing the ATX power and directly powering the board and HDD using a separate ATX power supply. Everything is working fine and I was ready to connect back the original ATX power connector from the E5071. The unit turns on for about 3 seconds. All fans work, CPU fan runs, HDD is on. But then everything just turns off and I have to cycle the front panel power switch to repeat the process.

Before I replaced the original motherboard, the unit turns on and produces no video. It stays running with a blank screen. Since I was able to use the original PCI CHIPS video card, it was confimed that the original motherboard went bad. There are no other power wires to the board other than a 20 pin ATX cable that comes from another board inside the E5071 unit (not directly from the ATX power supply). My guess is the power circuity controls everything, including supplying power to the motherboard. Even with the unit off, some parts of the unit remain energized, like the OCXO.

Im thinking it has to do with the motherboard and the agilent PCI hardware controller. Some "stay-on" signal isnt passing through. Any ideas would be appreciated.

[m k]

Some tower computers boot up like then after mains are lost, ACPI something I guess.

Maybe your new motherboard has a different setting somewhere.