This Satellite M70 has no battery.
When first connected to mains power, the blue power LED comes on as expected.
But after a few minutes the blue power LED goes off and all power is lost.
This happens even if the computer is not "turned on" while plugged in. So it is not likely to be overheating.
The longer it is left unplugged, the longer the LED stays on when it is plugged in.
If unplugged and replugged right after the LED goes off, the LED may not come on at all, or it may come on for only a few seconds.
I have completely disassembled this M70 and there is no dust anywhere inside.
The problem persists when the M70 is stripped down with no RAM, HDD, display, keyboard or interface cards. All parts I can reach feel cold when the power loss occurs.
The PSU is known good, it is 3.34A and reads 19.5V with a voltmeter.
So, probably something is wrong with the power components on the mainboard.
It's not really worth paying for repairs, so before I discard this M70, what else should I try?
Here must be some serious problem with power supply electronic placed on the mainboard.
In my opinion there is nothing you can do about it.
If you want to keep this old piece of hardware check eBay and maybe you can find refurbished mainboard and exchange it. Maybe you can find well working M70 but with destroyed or defective display and get it for less money. So you can use two notebooks and make well working one.
I don’t think you should spend a lot of money for it.