Fix TV Power on Switch

Problem:

TV does not turn on when ON button is pressed.

Debug

Power led stays red. It means the problem is after the power supply most likely.

First law of electronics is to check that the plug is inserted. This means checking the items directly related to the problem.

TV is powered by a push on switch. First test is to open the TV and check whatever the switch closes the contact when pushed with tester.

That's where the problem was. Power on switch failed and does not close the contact.

Repair Procedure

The failed component is just a bog standard push button. Objective is to replace the failed component.

Step 1: Find replacement part

A similar looking part is going to be removed from a random board.

Step 2: Desolder Replacement Part

First test the part to ensure the bad switch is not going to be replaced with another bad switch.
Second, use a soldering pump and a soldering iron to desolder the component.
Take care not to overheat the terminals too mucch since the casing of the switch is plastic, and will melt if abused too much.

Step 3: Desolder Failed Switch

Remove the bad switch from the TV board.
The switch is already dead, so take care of preserving the PCB tracks more than anything.

Step 4: Solder the good switch

Test the switch again to ensure it survived the desoldering.
Solder in the good switch on the TV board.
Ensure the solder joints are good. it's not hard for such large pads.

Step 5: Button assembly

Solder the button back on the TV board. Test it one final time and screw it back inside the TV

Step 6: Debug

Before closing the TV, see if the problem has been solved.
Original problem was that pushing the button did not turn the LED from red to green.
A quick test shows that the problem at hand is fixed.

Conclusions

As always in electronics, first tests switches and wires if device does not turn on. Switches in particulare suffers mechanical wear and are prone to failure. They are also very cheap and easy parts to fix. This time it was indeed a problem with a switch

If the wires and switches are OK, device is more than likely dead.

Another common point of failure are bad soldering joints on one of the many ICs, but for consumers electronics it might not be worth the trouble to check all of them, and they are quite a bit smaller and harder to check.

Another common problem are capacitors of the power supply. Unfortunately, if the power regulator was not up to the task, it might have damaged the internal electronics, and finding and replacing the bad capacitor wouldn't help.