Lg 50ps6000

[MOycanooo]

Hi all,

I have got a Lg 50ps6000 that sometimes does a strange noise like a Bippppp very loud that only goes when i turn it off.

It all startes by doing some noises like a BUM every 5minutes and then it goes for the loud bip... that will only stop if i turn it off.

it looks like it comes from the main av board EAX57566201(5)
how can i try to diagnostic more acurate?
and any suggestions on what it might be?

Many thanks.