Lenovo Thinkpad T540p 20BE no video

[Per Hansson]

Got a T540p 20BE-005YMS
It failed when the user tried to power it on with low/depleted battery.
I suspect that the BIOS is corrupted, is it possible to flash these with an external programmer?
(Or does any BIOS recovery mode exist on it? I've tried FN+B/R but nothing seems to happen).

First I would like to check it with a POST card but the laptop only has M.2 slots.
Does anyone know if it supports I2C via the battery interface?
If so thinking of buying something like this, already have one like it but without I2C & ELPC.
http://www.ebay.com/itm/5-in-1-Mini-...-/321806513125

I've removed SSD, battery, CMOS battery, WiFi card, keyboard etc.
But all that happens is that the laptop powers on when the power adapter is attached.
Fan runs at high speed then slows down and keyboard lights up, but no other activity.
I have tested the RAM in another system and it is ok.
I have also connected a screen to VGA & HDMI outputs but there is no activity.

The laptop is just out of warranty and has actually already had the mainboard replaced once under warranty.
The FRU of the current board is 00UP925
(Don't know the FRU number of the original board but suspect it could be 04X5264)

[Per Hansson]

Re: Lenovo Thinkpad T540p 20BE no video

Answering my own questions above:
The laptop seems to not support I2C via the battery interface, that is only for older Thinkpads.
I disassembled the laptop and found that the CMOS battery cable, which I had previously noticed was crimped between the PCB & magnesium frame was actually cut straight off!

I desoldered the BIOS chips and tried to read them in my Willem GQ-4X programmer:
The 8MB chip: MX25L6406EM2I-12G could be read.
The 4MB chip: MX25L3206EM2I-12G could not even be identified by the programmer.

So I ordered new pre-programmed chips on eBay and soldered them in, but still there was no video output.
The new chips are: W25Q32FVSSIG & W25Q64FVSSIG

So I took some measurements (have not located a schematic).
Inductor L36 sees 1.35v (DDR3L)
Inductor L8 sees 0.9v (nVidia GPU I think)
Inductor L37, L38, L39 see 1.77v

Obviously 1.77v is too high for the CPU but I've never looked at one so recent before.
It is a 4:th generation Intel Core i7-4700MQ CPU with SSPEC: SR15H so Haswell based with integrated VRM in the CPU itself.
What does 1.77v signify, does it mean the CPU is not communicating with the VRM?
Or is it simply the VRM input voltage and if I want to know the VCORE voltage I have to get my hands dirty?

[jasko_jacker]

Re: Lenovo Thinkpad T540p 20BE no video

In this video seems to be the corect core voltge..
https://www.youtube.com/watch?v=rwiiGGHsrxA

[Per Hansson]

Re: Lenovo Thinkpad T540p 20BE no video

Brace yourself, this is going to be a long read!
To answer my own question above yes 1.77v is normal for the Fully Integrated Voltage Regulator (FIVR).

I started looking for a replacement mainboard.
Now as I said earlier it had already been replaced so I didn't know the originals FRU number.
Therefore I had to go by visual look of the boards on eBay, I found one that looked exactly the same which I bought.
It arrived in a flimsy cardboard box.
Inside it lay loose in a US postal service paper bag inside an antistatic bag that did not even cover the whole board.
As there was no filling in the box the board had moved around in there, and cracked it's PCB.

But looking further this was the wrong PCB!
When ordering I had compared the board I had very carefully with the posted pictures.
But this had 4 RAM slots while mine had 2.
It had a 8-pin CPU fan header while mine was 5-pin

I thought ok no harm in trying it anyway and it actually posted, wow!
But due to the different fan pinout I could not test it.
Because if I tried to enter the BIOS or boot to a USB stick it just said CPU FAN Error and shut off.

Not amused with the seller I tried to do my first return claim ever on eBay.
It was both a learning experience for me (in frustration) and in the end no refund for me.
The seller was very clever: after starting a claim there is a specific amount of time I as a buyer have to return the item.
As the eBay instructions clearly said I should get a prefilled shipping document I awaited that.
But when nothing arrived in eBay's alloted time I opened a claim.
The seller again waited the maximum time before replying, at which time I was abroad.
So I could not ship back the item in the alloted time, and eBay ruled in favor of the seller.
So I was stuck with my broken board...

Not seeing much way out I decided to order a new CPU fan that fit the new connector directly from Lenovo.
Because at this time I had narrowed down that the board was not even for a T540p at all, it was either for a W540 or W541.
When the fan arrived I tried it and sure enough, as I got into the BIOS for the first time I could verify that it was a W540!
So now I installed Windows on the machine with the PCB bare on a table to check stability and it seemed ok!

So I ordered a touchpad with 3 physical buttons because the original is this stupid thing with no buttons.
When that finally arrived I reassembled the laptop, no missing screws after so many months passed!
For ease of installation I had used Windows 10 during my testing, but now noticed a problem:
The screen would intermittently go dark for a few seconds, I was quite sure this was a driver problem though:
Because Win10 had happily overwritten Lenovo's combined Intel / nVidia driver that has the graphics adapter switching magic in it.
And as I have grown a bigger hatred for Win10 the more I've used it I decided to put Win8 on it as the board has a license for it built into the BIOS.
But sadly the issue remained in Windows 8.1 with the right drivers installed

I have documented that issue in this separate thread but in the end what was necessary was to replace the 135W AC adapter with a 170W one.
I do find that a bit strange because the W540 and T540p are very similar (they use the same chassis).
The documentation for the W540 does state that if you get it with a quad core CPU it will come with a 170w adapter.
But the same CPU in a T540p and it comes with a 135W adapter.
The nVidia graphics card is slightly better in the W540, but it's not a significant difference... GT730M vs Quadro K1100M (33w vs 45w).

After all of this I might just settle on Win7, because I just checked and it does have a SLIC 2.1 table in the BIOS, did not think it would have that!
But I must say this laptop is fantastic, it has Lenovo's 2880x1620 IPS screen which is just amazing compared to my old trusty Eizo monitor!