Most modern desktop screens / TVs are of the back-lit LCD variety. There are 3 main components:

• a logic board (makes the picture)
• ** a fluorescent tube (generates light that is beamed through an LCD panel)
• ** a step down / step up power supply
  • voltage for the logic board is stepped down to about 3.5 to 9 volts
  • voltage for the fluorescent tubes is stepped up to about 15,000 - 25,000 volts

The items marked ** are prone to failure over time and there are very specific symptoms that escalate.

1) Red / orange tinge at start-up, then the screen seems fine

The fluorescent tube(s) is / are beginning to fail and take longer to warm-up. Over time the amount of time to warm-up increases until eventually the screen goes-black after a flew flickers and fails to start-up at all. The very brief red-tinge at start-up can however last for years. Fluorescent tubes can be replaced.

2) Cracking / hissing / high pitched noise, screen still working

This may go away after a few minutes or may be more persistent. The sound is caused by the high-voltage side of the power supply unit. The tops of capacitors may be beginning to bulge as they internally break-down. This is a good indicator that hardware failure is on the cards.

In this image below the top-right capacitor is beginning to bulge.

3) Louder sounds, an unpleasant smell, screen still working

The power supply circuit board is beginning to "cook". In the image below the darker-brown area at the bottom around the bulging capacitor is "cooked" circuit board. You should unplug from the mains ASAP. Fire is improbable but possible. It is possible that high voltages ie 15,00 volts + may leak to the logic board and possibly into your computer. Open windows quickly to vent the toxic fumes. The power supply circuit can often be replaced with a second hand unit.

4) Loud pop, unpleasant small and a blank screen

The "X" on top of the power-supply capacitors is there for a reason: when the internal pressure reaches a certain point the capacitor will rupture along the scored lines. When it does there is a loud pop. Carefully disconnect from the mains and open windows quickly to vent the toxic fumes ASAP. This type of failure can result in damage to other circuits and fire is possible. The power supply / logic board circuits can often be replaced - the LCD panel itself will probably be unaffected.

Repair or replace?

From an economic perspective replacement is often the best strategy because a failing power supply board may be followed by failing florescent tubes and visa versa. If you have the skills and you can buy a cheap second hand unit to cannibalise, then you may be able to create a working screen by combining the best parts of the 2 units. In many cases the only tools required are screwdrivers and patience!