Voltage regs are worth repalcing, I deal with a lot of power supplies where faulty capacitors overload the regs and cause them to fail.

Sorry, these days I am busy with the other things. I will report all the measurements later. What you said is right. I guess the Voltage regs are that two transistors which mount on the heatsink. Please check my photo.

 

 

I am not sure that two transistors are Voltage regs.
Since TV's power supply is Switch Mode Power Supply, my TV starts clicking as soon as I plug the TV into the power, does that indicates the IC chip is bad

 

I tested (2), only got 120V AC, unable to get 250V as the board says. I test (1), it supposes standby 5.1 V, the reading was very unstable, from 2,3,4,5, and kept rolling.

 

Here is the picture of the power board, I also indicated the point 1 and point 2, where I got the reading.