Sometimes when I switch the machine on there is no startup sound but speaker hum. If you play a game when this happens you have no sound. If you switch machine off and back on (sometimes it may take several switch off / on's) you get start up sound and sound works perfectly. You can sometimes switch it off and back on several times and sound remains. It is usually after you have not used machine for a few hours or so it has the issue but not always
Any help much appreciated