Weird problem with T400

[mattster]

I went on vacation and came back to a dead T400. No lights, no power, nothing. Tried numerous resets and power drains to clear things out. Still nothing. I did replace the motherboard and had things working for a day or so, but my LCD was also dead. I noticed the new motherboard had a really old BIOS on it, so I upgraded which went just fine. System rebooted, finished the flash and turned off. I turned it back on and went into the settings to reset a few things and turn some things off. I saved those changes and now it doesn’t appear to boot up. The cpu fan will spin a few times, but nothing beyond that. I can take the memory out and get the usual beep sequence for that.

I have also replaced the LCD, the LED board and LCD cable, as there were no lights before I changed the motherboard or after. With the new LCD in place along with the LED board, nothing. Although this evening, I noticed that the LED for the power was on very faintly when I powered up. Still not booting.

Does anyone have any ideas as to what might be going on? I have never seen something like this before with as many ThinkPads as I’ve owned and worked on in the past. Is there another reset of some sort I need to try? I’m about ready to throw in the towel and sell off this thing for parts, but want to see if anyone has ideas I could try.

Thanks in advance!
Matt

[Thinkpad4by3]

TAKE OUT EVERYTHING!!! Basically, put in a known good piece of memory and a monitor over VGA. No battery, wifi/wwan, ssd/ etc. If it boots then, put pieces in one at a time to see if it will boot.

[mattster]

Took out everything I could, used known good pieces (ram and monitor) and still nothing. I’m stumped here, after replacing everything.

Does anyone remember if there is a process to force a BIOS flash reboot from this state? I seem to remember some kind of process where booting from a floppy could possibly flash to a back level BIOS for recovery.

Aside from that, anyone need a parts machine potentially? New LCD included.