Dell Inspiron 3542 (Cedar_Intel-MB 13269-1) - RTC battery self-discharging and Realtek LAN issue

[danielsak]

Hello, I have issue with Dell Inspiron 3542.

Motherboard marking:

Cedar_Intel-MB 13269-1
PWB FX3MC REV: A00

The laptop works just fine (on battery and power supply) and doesn't cause any problems, except those described below:

1. The first problem is that the RTC/CMOS battery self-discharges after about 2-3 weeks after installing a new battery. I have been installing different batteries (GP, Duracell, Energizer) and the problem still exist.

1. The second problem is the LAN network card (Realtek RTL8106E), which is not detected at all in Windows. The BIOS is updated and the LAN network card (Integrated NIC) is set to <Enabled>.

Here is my measurements:

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

More measurements for that area (voltages and resistance measured to ground // resistance measured WITHOUT power supply, main battery and RTC battery):


Voltage drop on R2502 with only RTC battery connected: 45.8 mV (RTC battery was 3.14V at this moment).

I also measured Q1901 (with power supply and RTC battery when laptop is working):
- D (RTC_RST#) - 2.82 V is that normal voltage? With RTC battery only connected (without power supply and main battery) I have 2.76V on D (RTC_RST#) of Q1901
- 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 chip area) 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

Any suggestions?

Thanks for everyone.

Here is schematics and BoardView for that board: LINK to schematic/boardview https://www.badcaps.net/forum/troubl...urgent-13269-1

[danielsak]

Any ideas?

[rogfanther]

how are the measurements in diode mode for D2501 ?

[reformatt]

Gate of Q2505 resistance seems low to me. I would have expected 10 meg, unless Q2502 is leaky. Under normal circumstances when main (charged) battery or adaptor is plugged in, there should be no discharge of the CMOS battery as the RTC_AUX_S5 supply should be fed off 3D3V_AUX_S5 via D2501.

D2501 is a Schottky device, would expect under 200mv drop in diode mode for that.

As far as network card goes, Realtek ones die all the time and I just replace them.

[Spider1211]

danielsak Try replacing both D2501 and Q2505. There are known to be sometimes leaky if I recall correctly.