Lenovo T520 power up issue

[STh]

My Lenovo T520 (WIn 7) has been misbehaving for some time, showing two separate problems:
- It couldn't be powered down: after shut down it always restarted by itself and the only way to power it off was to press the power switch once more during POST. Disabling "auto start at AC power on" in BIOS didn't change that quirk.
- At power up, error message 1802 was displayed ("Unauthorized network card is plugged in - Power off and remove the mini PCI network card (05C6/9205). System is halted."). Pressing the power switch once more would allow a normal boot up, though.

So, there were a couple of workarounds to use the laptop. However, recenetly I decided to replace the WLAN mini PCi that I had a spare of, to see if the error would change. I know that the BIOS checks the FRU's and complains if some of the IDs don't match its internal list. (As I had done some HW tests with it a few years ago, I wasn't sure if the WLAN card was the original one or not.)
Before repacing the card, to ensure minimum impact I disabled the WLAN in BIOS, switched off the WLAN from the external side switch and removed the CMOS battery. (I don't mind restoring the BIOS settings again at the end.)

Strangely, after the card replacement the laptop didn't turn on again.
Nothing turned it on, with or without the CMOS battery or main battery.
The only sign of life (however very brief) is if the power switch is depressed (without the main battery) while the AC adapter is connected. Then the LED of the depressed power switch keeps blinking and if the switch is released, the laptop attempts to start (briefly blinking the red LEDs on the left side, as it would normally do) but then it shuts down and cannot be started at all. The behaviour can be reproduced if the AC adapter is unplugged and the same procedure is run again. The same thing also happens with the first WLAN card, if placed back in the system.

Exhibiting two opposite behaviours: previous automatic restart and now the imposibility to power it on, would indicate a malfunctioning PS functional block. I wouldn't consider the BIOS as the main suspect in this case.

Anyway, before opening up the laptop for a more thorough investigation, I decided to check if anyone in this forum faced this challenge so far and has some useful suggestions to follow.

Thanks in advance.

[Duranitron]

Re: Lenovo T520 power up issue

in my opinion erratic operation points to the bios, ddr ram or power problem .. try to check the bios battery first for normal voltage...check the vcc of the bios ic... flash the bios with good dump..check the memory with memorytest86.. check all the ALW voltage. 3.3 5v 1.5 1.28 post your progress here..

[mcplslg123]

Re: Lenovo T520 power up issue

A laptop not shutting down on shutdown command and rather restarts-this is most likely coz of PCI_Wake signal. Removing the lan chip may resolve this problem in most of the cases. However, it relates to PCH issues as well. So ,in your case, going by the original symptoms, it was likely a bad lan chip or PCH.

The current symptoms can be for many reasons and its difficult to guess it without physically checking the mb. You should open up the laptop and check for any visible damage,burnt corroded parts. Next measure resistance on all big grey coils to understand if there is any shorted rail.

Good luck.