Problem backlight lenovo s145-15ast

[eric35]

Hello ,

I have Problem of backlight on my lenovo s145-15ast.

I touched the lvds connector with the cable.
it sparked and now my screen is very dark.
I tested the f2 fuse and it seems good. it beeps with my multimeter in continuity mode.

[Vesko356]

Re: Problem backlight lenovo s145-15ast

Hello ,

I have Problem of backlight on my lenovo s145-15ast.

I touched the lvds connector with the cable.
it sparked and now my screen is very dark.
I tested the f2 fuse and it seems good. it beeps with my multimeter in continuity mode.

Will be in help if you add some more information. Do you have a picture without backlight, or both are missing?

For the convenience of the people helping you in solving the problem, schematic and boardview:
https://www.badcaps.net/forum/showthread.php?t=115603

.

[eric35]

Re: Problem backlight lenovo s145-15ast

we see the image if we illuminate with a strong light

[Vesko356]

Re: Problem backlight lenovo s145-15ast

we see the image if we illuminate with a strong light

There is a hope.
Check the fuses (3.3V and !9V rails) at the screen pcb itself. If the fuses are OK, we can start measuring, but for now check that first.

[eric35]

Re: Problem backlight lenovo s145-15ast

I tried another screen and the image is also very dark

[mon2]

Re: Problem backlight lenovo s145-15ast

What is the voltage to ground on each side of this fuse (F2) ?

Confirm the same voltage reaches the display connector. Do this carefully.

[eric35]

Re: Problem backlight lenovo s145-15ast

I don't know how to do that unfortunately

[mon2]

Re: Problem backlight lenovo s145-15ast

Meter in dc volts mode.

Red probe to one side of fuse.

Black probe to ground. Check the measurement.

Repeat with the other side of the fuse.

Post all readings.

[eric35]

Re: Problem backlight lenovo s145-15ast

20.1 on each side

[mon2]

Re: Problem backlight lenovo s145-15ast

Confirm the same voltage is able to reach the LCD display connector - see attached and check where the arrows are shown.

To be safe, remove all power. Meter in DIODE mode. Short the meter probes and should hear a beep tone.

Next, one probe on either side of the fuse @ F2, other meter probe to the arrows in the attachment. Do you hear the tone beep?

[eric35]

Re: Problem backlight lenovo s145-15ast

I have 0.6 everywhere

[eric35]

Re: Problem backlight lenovo s145-15ast

I got the wrong motherboard. I have one where there is no sign of life and on the one in continuity the fuse f2 is good but on the motherboard where I have a very dark display no beep in continuity mode.

[eric35]

Re: Problem backlight lenovo s145-15ast

I don't know how to change the fuse

[PochoMellit]

Hello people! Please excuse my English, but I'm from Argentina and I don't speak English properly (but I can interpret by reading). If the voltage and diode values are normal, could we conclude that the fault is in the LDC flex or should we continue with the measurements at other place?

[rogfanther]

If you have access to another flex cable, it is easier to try with it, to not risk shorting some lines when probing. If after trying with *correct* cable and screen it still do not show image ( but shows in vga/hdmi ) , then you can measure other points to see if the Enable signal is being generated.