Acer Aspire 7520, usually will not charge.
If I use the battery, with no mains supply, then it works correctly. I can boot into either the Windows Vista or the Ubuntu operating system installed on the computer.
When I connect the mains supply, the Power Supply flashes orange, and the Computer On light flashes green, both synchronised and continually flashing at about one flash per second. The battery is not charging. (The battery monitor shows a steadily diminishing charge, and the Power Supply remains cold.)
If I unplug the power supply, then the Computer On light is continuous green, and the computer works ok.
If I re-connect the power supply, then both lights flash again.
The battery is showing over 50% charged,
The open-circuit output of the Power Supply, measured on a digital voltmeter, is the expected 19.4 to 19.6 volts.
Sometimes it all works correctly, the lights do not flash, and I can continue as normal, Most times it fails.
I have removed the battery and held the On button down for 20 seconds, several times, to no avail.
The Power Supply seems to be working correctly, the battery seems to be partially charged.
Why are both the Power Supply and the Computer On lights flashing?