If you try another source...and it's still present. Then I'd doubt PSU.
If it is not present then its possible one of the the PSU voltages is low. 33V is is used a lot in tuning sections. That said these modern TVs monitor their output voltages for fault, but not all voltages. Could even be noise on a voltage line.
TV PSU have been a plague since way way back in CRT days, I was fixing TVs back in 1980's.
These modern TVs/LCD PSU also fail. I fix many and you would be surprised at it's always the same components, "switchmode power supplies". Mainly due to the
capacitor plague on not only computers but all electronics, but also due to high ripple demands on capacitors.
Anyway I digress....try the above. Try a TV repair they don't charge much if it's a switchmode issue (bread and butter repairs) but if it's something else...well the TV is quite old compared to todays new generation stuff and todays equipment is cheaper and better. A Tech could spend too much time fault finding than the cost differential saved to but a new one.
Aldi have a 55" LCD $599 (11 oct sale, my store still has them). I have 2 Aldi TV, one running since 07...! Cannot complain about them.
