no MrJoe, this wasn't a problem that came after an update (if that is what you mean). As suggested i did try booting from usb but same conditions persist during booting from usb as well (initially, ie when the system is turned on and desktop appears, sound is there but after few minutes sound disappears, i checked by using test speakers option in sound settings after few minutes while i booted from usb). Just in case if my problem isn't clear, this is what i am facing. i installed linux mint (not dual boot, erase disk and install linux option), but soon found out that sound disappears after few minutes from SPEAKERS, but headphones work fine (thank the gods
) i went through suggestions like force starting alsa, installing pavu control etc. i tried kernel versions (4.4x as well since this is an old model laptop). but other than changing the duration( 10 minutes max) for which speakers work, problem was still there. i thought it might be audio card going to power saver mode (found something on net to change a value to 0 on /usr/lib/pm-utils/power.d/intel-audio-powersave) but it too didn't give desired results.( plugged in or not sound works for few minutes then goes off) . but there tabs showing sound playing in pavu control, sound settings shows audio playing but there is no sound from speakers as i posted on previous replies. Forgive me if i haven't made my problem clear earlier.
thanks.