HITACHI 58HK6100UA

[Runlinc]

When changing channels the top quarter of the screen is dark for 3 seconds before lighting up as normal.
This happens every time I change channels and is consistent. After the top backlights come on the picture is good.
I think there are only 4 sets of backlights in this tv, do you think it's the top row failing or a panel issue or panel driver
problem? Or am I totally wrong?
Many thanks for any help.

[Davi.p]

The fault is 80% the top led bar, the rest is the bar connector, and the led driver if each bar has its own driver (bad diode contact, bad final electrolytic)

[Runlinc]

Many thanks for your reply, I will investigate further.