T.v wont switch on. my t.v is only 5mths old and we have not llong moved house and cant find the

Question

my t.v is only 5mths old and we have not llong moved house and cant find the receipt for it so asda wont take it back. The t.v was working fine then one morning it switched its self of and i carnt get it to work anymore. it will go onto standby but maks a quiet whissling noise but thats all i can do.