T470 frustration

[jruschme]

I recently picked up a "for parts" T470 along a partial second one and a third motherboard from eBay... and can't get any of the motherboards to do much of anything. The "best" of the three will momentarily turn on the power lights and keyboard backlight when a square charger is plugged in and when I press the power button. There are, however, no sounds from the speakers or other signs of life. The other two motherboards seem to be completely dead.

I've tried all the usual tricks to try and get one of them to POST- disconnect batteries and hold power button, both short and long presses of the reset button, swapping RAM, etc. None of these has made any difference. I'm also pretty sure that the square charger port is not an issue.

I'm using a 90W adapter, so there should be enough power. Unfortunately, the internal battery seems to be dead and I don't have a removable battery, so I don't know if that would make a difference.

Are T470 systems particularly problematic? Is there any standard advice beyond what I've tried so far?

Thanks...

[RealBlackStuff]

Remove both internal and external batteries, and also the RAM.
Check that the CMOS battery is between 2.7V - 3.3V, then try to boot from the charger only.
If you hear 1-3-3-1 beeps (for NO RAM), put 1 RAM in, then try again.
If OK, add the 2nd RAM and try again.
Assuming the charger is OK, if none of these work on any of the 3 mobos, flog the lot or parts.