I’ve just started experiencing a problem with a Vaio PCG 6L1M.

Working off the battery power all works fine. But since a couple of days ago, when you plug in the mains adaptor the screen goes so dark as to be almost unreadable. The Fn+F5/F6 keys don’t do anything at all.

VAIO display power settings have power saving mode switched off for mains and battery power, and if I use the VAIO display control panel to reset the display brightness to 5 then hit apply and OK the screen brightness goes as it should for about 15 seconds, then goes back to being gloomy and headache-inducing.

Anyone experienced this problem and able to suggest a resolution?

Thanks in advance.