Old LCD no picture I'll try and fix it

[WatchTower]

How do these people who fix TVs determine what's at fault. I mean if it's just a bad capacitor I could pop up an Electronic store and to buy a new one and attempt to fix the TV myself. The problem is how do these people that fix TVs find out what's causing the fault? I mean sometimes there may be no visual damage to the components of an electrical device.

If I'm asking to much or it would be to hard to explain no problem.

But thanks for readying my question anyway.

 

[Sinopa]

How do these people who fix cars determine what's at fault?
How do these people who fix patients determine what's at fault?

They learn their trade and then make use of what they have learned.

For components with no visual sign of failure they have test equipment to measure them with.