Hello JA Customer I have been fixing Tv and Electronics since I was 5 years oldWith better than 20 years experience and 17 years in business
I cant believe you followed that up with
"Then the picture is fine"
I guess the first place we need start is to look at the power supply
I have seen some strange stuff
Since your pix returns to normal we may have some hope that this is not a bad LCD panal
and may be able to fix it
Check the power supply for Puffy and bloated looking capacitors
the tops will not be flat
If you have this issue you will know right away
So open the tv and get back to me
well, the back is off. nothing looks bloated, or burnt, or out of place.
Can you take a pix of the power board?
and u/l it it would be nice if i can see what you see