Lenovo V15 g2 ALC no backlight

[djob1981]

Got no backlight on this laptop, checked fv1 fuse was bad so replaced it with a new one and replaced the shorted cap next to it and l aso replaced the lcd cable as pin3 on the cable was burned. I now get 20v at those pins and get an image on ther laptop screen but still no backlight.checked fa2 fuse and is fine but gets no volts(unsure if this is right) and has a 0.33v drop to ground when testing ..

Anyone got ideas where else i should look

[djob1981]

also tried 3 screens same issue

[tomodachi]

Did you make sure +LCDVDD voltage is present ?

[djob1981]

Did you make sure +LCDVDD voltage is present ?

uv1 has no voltage on input side with just charger plugged in and board out of laptop

[djob1981]

When turned on pin 1 on uv1 fluctuates, pin 4 get 3.3, pin 5 has 1.8v, pin 3 is 3.3v

[djob1981]

fa2 fuse gets a solid 3.3v when turned on and fv1 20v

[rogfanther]

Measure resistance to GND on pin 5

[djob1981]

Measure resistance to GND on pin 5

i get 94.5k on pin 5 of uv1

[PWiKua]

did you find solution? i have exact same problem. i even changed EC chip and problem not fixed.

[mon2]

Link a schematic (if available). Post inside of the schematic forum if required.

Share the voltage to ground of each pin on the UV1 load switch that is used by the backlight.

[PWiKua]

here is shcematics and boarview that i got. its bit different but same board.
ic is SY6288C20AAC. my board has no displey nor HDMI output. every rail turns on as supose to.
i tried bunch of Bios but nothings change. there is no EN signal on UV1. board do not have UC3 but have UC4 and its also not enabled what i remember. i'll check everythin again

[mon2]

What are the silk screen markings of the actual board you are attempting to repair? What is the current draw of the board?

[PWiKua]

its HV461&hv561 NM-D522 Rev:2.0

[SMDFlea]

here is shcematics and boarview that i got. its bit different but same board.
ic is SY6288C20AAC. my board has no displey nor HDMI output. every rail turns on as supose to.
i tried bunch of Bios but nothings change. there is no EN signal on UV1. board do not have UC3 but have UC4 and its also not enabled what i remember. i'll check everythin again

The boardview has already been posted. Please post your schematic in this thread topic where other members will be able to find it -> https://www.badcaps.net/forum/troubl...-and-boardview

[PWiKua]

On UV1
1. +LCDVDD - 0V - 9.1M
2. GND
4. ENVDD - 0.002v (sometimes) - 10k
5. +3VS - 3.3V - 10k

on UC4
1. GND
2. CPU_EDP_PWM - 0v - 100K
3. GND
4. PANEL_PWM - 0v - 98.6k
5. +3VS - 3.3v - 10k

also when i started working on it there FV1 fuse was blown

[mon2]

Have you attempted the bios images found on internet on Vina site? They came up in the search engine.

Any sign of life if you remove the memory modules (assuming they are removable). Does the logic board complain?

when i started working on it there FV1 fuse was blown

Measure the resistance to ground on each leg of FV1 (without power to the board). Checking for a short condition.

[PWiKua]

resistance on FV1, both side its 40K

about memory. i'm using only soldered memory. also tried many bios versions from different sources. non of them worked

[PWiKua]

also i did not mentioned that cpu power mosfets getting much hotter then actual CPU

[mon2]

Likely the CPU is dead but suggestion is to replace each CPU linked mosfet AND their drivers.

[PWiKua]

OK thanks for help <3