Tim Downie wrote:
I've got a friend's ASUS M5200 laptop that I've offered to look at.

It works fine when connected to it's power supply but dies instantly if
the power is removed. There are only ever two lights on on the front of
the laptop, one for the mains supply and one for the hard drive. The
battery light never comes on. The power meter in Windows does identify
the battery and shows it as having zero charge.

I've tried battery recalibration and a new battery has also been tried
but neither helps, it still refuses to charge. More in hope than in
expectation I've opened it up to have a look around but there's nothing
obvious to see.

I'm guessing something has gone wrong with the internal charging circuitry.

Is there anything else I can do or have I come to the end of repair
options (short of motherboard replacement)?

Tim

Remove the battery and see if you can measure the voltage present at
the terminals the battery connects to while the charger PS is plugged
in. If you see no voltage there, it is a safe bet that the internal
components of the charging circuit are at fault. If there is voltage
there, you might consider the possibility of the terminals not making
proper contact with the battery.