Lenovo Legion Y520-15IKBN Display works only through HDMI

[Andreasbest]

Hello!
I received a Lenovo Legion Y520-15IKBN with blank screen but working display though HDMI.
Since customer was curious and disassemble it himself before bring it to me i want to check the JEDP1 backlight fuses but i can't find them!
Can you please point them to me?

Thank you in advance!

Schematics & Boardview attached

Boardview - https://www.badcaps.net/forum/troubl...nm-b191-rev1-0

Schematic - https://www.badcaps.net/forum/troubl...post1352445

[Andreasbest]

JEDP1 voltages pin#:
1 20v 11 0v 21 0v
2 20v 12 0v 22 0v
3 20v 13 0v 23 3.3v
4 20v 14 0v 24 0v
5 0v 15 0v 25 0v
6 3.3v 16 0v 26 0v
7 3.3v 17 0v 27 0v
8 0v 18 0v 28 0v
9 0v 19 0v 29 0v
10 0v 20 0v 30 3.3v

[mcplslg123]

Fuse is ok as you're receiving +LED_VDD on pin1-4 of edp connector.

Voltage on pin 8-9-10 is incorrect.

Pin10 EDP_HPD at zero volt may indicate a faulty cable as the edp cable seems not detected.

[Andreasbest]

So you suggest to measure again just for confirmation and if voltages the same, order a new cable?

[MontyL]

I'd disconnect, clean and reconnect first.

[FriedFred]

Backlight fuse can also be on the inverter board, not mainboard. As far as I can see on page 35, there is no BL fuse on mainboard.
So, if you have 20V at JEDP1, and you can observe something like a picture trough a torch lighting into the display, then you need to check whether the 20V find its way onto the inverter board inside the display.

[Andreasbest]

I disconnected, cleaned with contact cleaner and connect it again firmly. No luck.
Should i remove the screen bezel and measure the other side of the LVDS cable too?

[mcplslg123]

Measure resistance to GND on pin 8-9-10 of edp connector
01.With edp cable connected
02.Without edp cable connected.

Under both circumstances, NO POWER attached.

Please confirm its a no display on internal screen or Dimm display on it.

[Andreasbest]

Measure resistance to GND on pin 8-9-10 of edp connector
01.With edp cable connected
02.Without edp cable connected.

Under both circumstances, NO POWER attached.

Please confirm its a no display on internal screen or Dimm display on it.

Goodmorning from Greece.
Just returned to bench.
Measurements below
With EDP cable connected:
Pin 10 17.62κΩ
Pin 9 84.6kΩ
Pin 8 89.6kΩ

With EDP cable disconnected:
Pin 10 85.10kΩ
Pin 9 42.3kΩ
Pin 8 99kΩ

No display on internal screen. I see nothing with torch, i even entered BIOS that are many graphic elements but i see nothing.

[pc_okay]

Hello,

Do you try With another Working screen ?

[Andreasbest]

No, i haven't disassemble the lcd bezel yet but i'm about to do it in a few minutes to measure the fuse and the edp cable.

[Andreasbest]

With panel replacement works great, indicating something wrong with the screen itself. I'll measure all fuses on LCD board and report back.

[Andreasbest]

Fuse F1 32v 1.5A is blown.
Gonna replace it and report back.

[Andreasbest]

Fuse replaced, still no display, fuse not blown after two tries but nearby capacitors seem shorted, desolder them all and short remains on pads, solder them back. Out of ideas (except screen replacement).

[pc_okay]

Can you send photo of the LCD board?
Maybe it's another component that's shorted to ground.
Compare resistance to ground with the working one.

[Andreasbest]

Sure, screen model is LP156WF6 SP K6
The green marked components, mostly capacitors, were desoldered and short remained, the red marked not desoldered yet.
All of them seem shorted to GND, both pins.
The other screen i tried is not exactly the same model so can't use it for measurement comparison.

[Andreasbest]

Desolder the last 2 capacitors that seemed shorted, no problem there either. The short is elsewhere.

[pc_okay]

It could be a lot of thing not only caps…
Everything connected to This Line is suspect, and you can't desolder everything…

I never repaired screen but I think you can try to inject low voltage on the fuse if resistance is super Low (compare With other screen)
DON'T inject With motherboard attach or EDP câble…
Check With thermal cam if something heat.
Up voltage graduatly if nothing seems to heat.

[Andreasbest]

Main IC got very hot, so i guess the short is there.
Ordered a new screen. Thank you all!