Lenovo Legion 5 15IMH05H NM-C911 - brak obrazu

Witam,

Lenovo Legion 5 15IMH05H NM-C911 Rev: 1.0

Laptop trafił do mnie na brak obrazu po HDMI, jednak okazuje się, że już od dawna nie miał również obrazu na matrycy.
Jakiś serwis stwierdził że nie ma części do niego aby to naprawić i właściciel korzystał z laptopa po HDMI (i teoretycznie zależy mu jedynie aby tą funkcjonalność naprawić).

Laptop uruchamia się normalnie, wchodzi do systemu - słychać melodie powitalną Win11. Brak obrazu na matrycy, HDMI oraz po USB-C.
Bios podmieniany na inny, bez zmian - Win11 uruchomił się. HDMI oraz taśma matrycy przedzwoniona.
Brak napięcia na PL3102, rezystancja około 2-3 ohm.
Brak napięcia na pin 4 z UG9.
Reszta przetwornic wygląda, że pracuje prawidłowo.

Proszę o pomoc w diagnozie - wracam do tematu naprawy elektroniki po kilku latach przerwy przez budowę domu

Check UR3.

UR3 not exist on my motherboard.

Perform the following measurements while the machine is booted into the OS:
- Measure the voltages to ground on pins 15, 16, 18 of HDMI connector with the external HDMI screen connected.
- Measure the voltage to ground on pin 19 of HDMI connector with and without external HDMI screen connected.

Pin 15: 4,24 -> 4,96V after OS booted
Pin 16: 4,35 -> 4,96V after OS booted
Pin 18: stable 5,09V
Pin 19: 0,2V without external HDMI screen

Oh, sorry for that - voltage is something around 5V with external HDMI screen connected.

Measure the following voltages to ground with and without external HDMI screen connected:
- On pin 1 of transistor QG4.
- On pin 3 of transistor QG6.

Transistors QG4, QG6 pinout:

With and without HDMI screen connected values are the same
- Pin 1 of QG4 = 1,8 V
- Pin 3 of QG6 = 0,2 V

Sometimes (random reconnect) with HDMI connected is 2,8V on QG6 pin 3 then on QG4 pin 1 is 64mV.

Measure the following voltages to ground with and without external HDMI screen connected:
- On all pins of transistor QG6.
- On both pins of resistor RG58.

QG6 with and without HDMI: 1 - 0,2V; 2 - 3,3V; 3 - 0,2V
RG58 with and without HDMI: 0,2V and 105mV

One time (random reconnect) on RG58 was 4,96V and 0,5V probably.

Use a continuity tester and check the following connections:
- Between pin 19 of HDMI connector and pin 2 of resistor RG58.
- Between pin 19 of HDMI connector and pin 1 of transistor QG6.

Those connections have 0 Ohm, but I found small problem with losing connection on HDMI port with pin 19. After resoldering now everytime with HDMI connected is 2,8V on QG6 pin 3 and on QG4 pin 1 is 64mV. RG58 have 4,96V and 0,57V.
Checked again connections between HDMI pins on MB and 2nd end of HDMI cable. Looks good.

Still no video on HDMI.

Please, remeasure the following voltages to ground with and without external HDMI screen connected:
- On pins 1, 2 of transistor QG4.
- On pins 1, 3 of transistor QG6.

Thank you for answer!

With HDMI:
QG4 pin 1: 65mV, pin 2: 0,58V
QG6 pin 1: 4,98V, pin 3: 2,81V

Without HDMI:
QG4 pin 1: 1,81V, pin 2: 106mV
QG6 pin 1: 0,21V, pin 3: 0,21V

Set your multimter to the diode test mode and measure te following voltage drops to ground:
- On pin 1 of capacitors CG32, CG33, CG34, CG35, CG36, CG37, CG38, CG39.
- On pins 1, 4 of transistor QG3.

CG32, CG33, CG34, CG35, CG36, CG37, CG38, CG39 pin 1: 0,314V on all capacitors

QG3 pin 1 and 4: 0,622V on both

Measure the voltages to ground on all coils.

All looks good, in first post was information about missing voltage on PL3102:

DemoNx4 napisal/-a:Brak napięcia na PL3102, rezystancja około 2-3 ohm.
Brak napięcia na pin 4 z UG9.
Reszta przetwornic wygląda, że pracuje prawidłowo.

But if you want, I can check it again and post here later all values.

Sorry for the long reply time - my son was born

PL1401: 0,964V
PL3201: 0,996V
PL3001: 0,967V
PL3002: 0,966V
PL3003: 0,966V
PL3004: 0,966V
PL3102: 0V
PL8201: 1,202V
PL8202: 1,204V
PL7501: 0,751V
PL7502: 0,756V
PL7503: 0,759V
PL2701: 1,228V
PL2001: 3,31V
PL2002: 5,12V
PL1301: 1,067V
PL101: 0,219V