How to test LCD screen inverter in a laptop

In this post I explain how I test the LCD screen inverter board in a laptop computer.
The screen inverter failure is very similar to the backlight lamp failure. In both cases the screen gets very dark and the image on the screen becomes very faint, barely visible under a bright light.
If you suspect the inverter board failure, I know only one reliable way to test that. It’s either replacing the inverter board with a known good one and see if it works, or connecting a known good backlight lamp and see if your presumably bad inverter lights it up.
In most cases I go with the second method – testing the laptop with a known good backlight lamp. Why? Because backlight lamps are pretty much universal. The same backlight lamp will work with many different inverters as long as they have matching connectors. I’ll talk about these connectors later.

Repair Mainboard

Step 1: Power button:
If there is power step 2, otherwise check power supply circuit , including: stand by 3v3 , chip SiO, Southbridge.

Standby 3V3:
- 5v standby voltage from ATX will lower down to 3v3 for the southbridge, often using an ic 1117 or 1084, 1085, 1086 (pin 3; input ATX STB 5V, pin 2; output 3v3 STB. The main life bulbs are not used IC which uses a circuit with few or MOSFET transistor to stabilize pressure.).

- Check 3V3 at A14 pin PCI slot (see picture).