Dell Inspiron 3542 - samoczynne rozładowanie baterii RTC i problem z LAN Realtek

Witam,
laptop to Dell Inspiron 3542, poniżej oznaczenie płyty głównej:

Cedar_Intel-MB 13269-1
PWB FX3MC REV: A00

Laptop działa w pełni poprawnie (na baterii i zasilaczu) i nie sprawia żadnych kłopotów, poza tymi opisanymi poniżej:

1. Pierwszy problem to samoczynne rozładowanie baterii RTC/CMOS po około 2-3 tygodniach od montażu nowej baterii. Montowałem różne baterie (GP, Duracell, Energizer) i problem się powtarza.

2. Drugi problem to karta sieciowa LAN (Realtek RTL8106E), która w ogóle nie jest wykrywana w systemie Windows. BIOS jest zaktualizowany i karta sieciowa LAN (Integrated NIC) jest ustawiony na <Enabled>.

Wymieniłem tranzystory Q3001, Q3004, Q2505 oraz podwójną diodę D2501 na zupełnie nowe. Karta sieciowa wciąż jest niewykrywana, więc obawiam się, że jest uszkodzona.

Nie mam możliwości wylutowania układu RTL8106E.

1. Czy mogę całkowicie wylutować tranzystory Q3001, Q3004 by odłączyć zasilanie od układu RTL8106E bez jego wylutowania? Używam tylko sieci bezprzewodowej, więc takie rozwiązanie również mogę zaakceptować

2. Czy to samoczynne rozładowanie baterii CMOS może być związane z uszkodzeniem układu RTL8106E?

Rezystancja na plusie gniazda baterii RTC względem masy wynosi ~731 kΩ

Z góry dziękuję za pomoc.

Hello!

- Measure the resistance to ground on pin 3 of diode D2501 (with the power supply, main battery and RTC battery disconnected from the board).
- Measure the voltages to ground on pins 8, 12, 15, 16, 19, 20, 21, 23, 28, 29, 30, 32 of LAN chip LOM30, when the machine is turned on.

Diode D2501 pinout:

Resistance to ground on pin 3 of diode D2501 - 147 kΩ and it's slowly rising.

D2501:
Pin 1 (3D3V_AUX_S5) - 3.3 V
Pin 2 (RTC_PWR) - 3.14 V
Pin 3 (RTC_AUX_S5) - 3.02 V

Here is more measurements of voltage and resistance on that area:


I also measured Q1901:
D (RTC_RST#) - 2.82 V is that normal voltage?
G (RTCRST_ON) - 0 V
S (GND) - 0 V

Yesterday I put a new CR2032 battery, which was 3.29 V out of the box and now it is only 3.14 V.

Here is rest of measurements (LOM30 - LAN Realtek) when machine is turned on:
8 (VDD10) - 1.05 V
12 (CLK_LAN_REQ4#_R) - 0 V
19 (PLT_RST#_LAN) - 3.37 V
20 (ISOLATE#) - 3.15 V
21 (PCIE_WAKE#) - 3.33 V
23 (VDDREG) - 3.37 V
28 (LANXIN) - 0.73 V
29 (LANXOUT) - 0.48 V
30 (VDD10) - 1.05 V
32 (3D3V_LAN_S5) - 3.37 V

I was unable to measure pin 15 (CLK_PCIE_LAN_P4) and pin 16 (CLK_PCIE_LAN_N4) - unfortunately my measuring probes are too big.

strusmig wrote:I also measured Q1901:
D (RTC_RST#) - 2.82 V is that normal voltage?

Depending on the conditions under which the measurement was taken. If it was taken with the RTC battery connected only, it seems normal to me. In case it was done with the power supply connected, I expect a slightly higher voltage.

- Set your multimeter to the diode test mode and measure the voltage drop to ground on pin 12 of LAN chip LOM30 with both polarities of test leads (with the power supply and main battery disconnected from the board).
- Measure the voltage across resistor R2502 with a functional RTC battery connected only (with the power supply and main battery disconnected from the board).

- Does the machine retain the date and time settings in the BIOS with a functional RTC battery connected after the power supply and main battery has been disconnected for a while?

strusmig wrote:unfortunately my measuring probes are too big.

The cheapest solution is to buy a thin probe adapters as in the picture below. You can find them online by the therm "multimeter needle tip adapter".

matic wrote:Depending on the conditions under which the measurement was taken

With RTC battery only connected (without power supply and main battery) I have 2.76V on D (RTC_RST#) of Q1901. That previous 2.82 V measurement was with connected power supply and machine was turned on - "no bootable device" on screen.

There is also difference between RTC_RST# and SRTC_RST# - with RTC battery and connected power supply (machine turned on) there is:
RTC_RST# - 2.82 V
SRTC_RST# - 1.75 V

DSWODVREN - 2.93 V
PCH_INTVRMEN - 2.93 V
SM_INTRUDER - 2.75 V

matic wrote:Set your multimeter to the diode test mode and measure the voltage drop to ground on pin 12 of LAN chip LOM30 with both polarities of test leads (with the power supply and main battery disconnected from the board).

Pin 12 (CLK_LAN_REQ4#_R):
With black probe on ground: 940 mV
With red probe on ground: 480 mV

matic wrote:Measure the voltage across resistor R2502 with a functional RTC battery connected only (with the power supply and main battery disconnected from the board).

Voltage drop on R2502 with only RTC battery connected: 45.8 mV
Voltage drop on R2502 with power supply and RTC battery connected (machine working): 1.2 mV
RTC battery have 3.15V at this moment.

matic wrote:Does the machine retain the date and time settings in the BIOS with a functional RTC battery connected after the power supply and main battery has been disconnected for a while?

No issue with that, but I will check that again and tell you in next reply. Everything is fine until RTC battery discharges around 3V in two-three weeks and then laptop won't turn on.

Jakieś inne pomysły?

- Check the resistance between pins 1, 4 of resistor array RN1901 (it should be around 20kΩ).
- Measure the voltages to ground on pins 1, 4 of resistor array RN1901 with the RTC battery connected only.