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**ktmmotocross** · 03-24-2021, 05:49 PM

Re: Dell E6540 starts with Jack, but not with Power Button

what u measure on starting pin on KBC?

**mcplslg123** · 03-25-2021, 04:24 AM

Re: Dell E6540 starts with Jack, but not with Power Button

RTC Section failure. Check RTC section thoroughly.

**pingaroon** · 03-25-2021, 11:07 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Hi, I can't find any continuity between the 3v pin of the power button and either of the SMSC chips. Even on another board. But I don't know if that is normal or not?

I am into new territory here, so I am not sure how to even begin debugging the RTC section..

Could you give me some specific pointers how to test the RTC section?

Presumably the startup chip is responsible for interpreting both the power button press and the RTC battery, so is this looking like a faulty startup chip?

Thanks for your help (and patience)

**Spider1211** · 03-25-2021, 12:02 PM

Re: Dell E6540 starts with Jack, but not with Power Button

When the board is booted in OS, does pressing the power button have any effect? It could be that the trace from the power button to the SIO (startup chip) is broken or a dead component on that line.

Unfortunately (as per attached schematic atleast), it seems the SIO is a BGA type, so you can't directly probe its solder points. Try to request a boardview in the schematic section for your laptop model.

Here is what I would initially check:
1. Continuity from power button (POWER_SW#_MB) to pin 2 of R811
2. Pin 1 of R811 to closest point of POWER_SW_IN# you can find to the SIO.
2. Check if R811 is OK.

Attached Files

Dell Latitude E6540 VALA0 la-9411p.pdf (4.58 MB, 42 views)

**pingaroon** · 03-25-2021, 02:26 PM

Re: Dell E6540 starts with Jack, but not with Power Button

Hi,

I have searched all over the board for R811 but I can't find in. As you suggested, I have put in a request in the schematic section for a boardview. Perhaps the 8412p board I have is slightly different?

When the board is booted into the o/s, the power button still does not respond.
I've inspected the board visually and can't see any obvious signs of damaged traces or any irregularity of any kind.

The SIO looks like it is U51. The schematic has POWER_SW_IN coming in at B67. (I am confused why there are 2 pin-labelling systems A and B. The chip has 64 pins, so where is B67???. Page 46 of the schematic ) Presumably there should be continuity between the power button and this incoming pin? But I can't find it - where is B67 on a 64-pin chip?! I have needle-point probes, so can connect to each pin taking great care. None of the 64 pins of U51 have continuity with the power button.

I have further discovered the following:

When the laptop is off, the power button is still reading 2.5V !! This is coming via some route from the bios battery. That does not seem normal at all (the bios battery on its own measures exactly 3v). When the laptop is on, the power button measures 3.0v, but the capacitor right next to it measures 3.3V.

My head is hurting.

Thanks always for your help

**Spider1211** · 03-25-2021, 02:58 PM

Re: Dell E6540 starts with Jack, but not with Power Button

Per schematic, sio is an MEC5075, can you confirm you have same? Its actually an DQFN package (not BGA as initially mentioned). It has 2 rows underneath the chip, row A and row B. What you see soldered on the side is one of the 2 rows, check its datasheet to confirm which is which.

Presumably there should be continuity between the power button and this incoming pin?

Per schematic, R811 is in series, so I would expect to see 10Kohm between power switch and pOWER_IN_SW#

**pingaroon** · 03-25-2021, 03:53 PM

Re: Dell E6540 starts with Jack, but not with Power Button

ah thank you - yes that explains it - 2 layers!. It is a MEC5075. There are 68 hidden pins on the inside (B), and 64 visible (A). So B67 which connects to the PB is inaccessible to do any continuity check.

It seems I need to keep on hunting down R811 which is between the 2 in order to make progress.

What I don't get is why the bios battery voltage is getting through to the power button though?? That can't be normal. 2.5V is on the pb with the charger unplugged

Thanks

**Spider1211** · 03-25-2021, 04:04 PM

Re: Dell E6540 starts with Jack, but not with Power Button

What I don't get is why the bios battery voltage is getting through to the power button though?? That can't be normal. 2.5V is on the pb with the charger unplugged

Its coming as +RTC_CELL from the coin cell through PD3 -> R810. To confirm, you can remove the coin cell, it should go to 0V.

**pingaroon** · 03-28-2021, 10:30 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Hi folks, I'm really struggling here.

I actually replaced the startup chip from another old board which was successful but the original problem remains!

I have attached photos :
IMG8845. There is continuity between the PB and JAPS1 (6th pin down as shown). However, I can't find any continuity from this pin to anywhere else on the board. This image shows where the SIO would be (I removed it from this board to put on the board I am trying to fix). None of the pins in set A or B have continuity with the power button

IMG8846 shows where 3v measures on the PB

IMG8848 shows the fresh RTC battery and 3 resistance measurements on 3 resistors (1K, 10K and 50 Ohms). These are not labelled so I don't know if these are the R811 mentioned earlier??. None of these have any continuity with the power button

Can anybody help?
Thanks

Attached Files

**Spider1211** · 03-29-2021, 03:48 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Per schematic you wont get continuity from power button to SIO since R811 is in series. Put your meter in resistance mode and measure resistance (remove coin cell before measuring) between power button and B67 of SIO, I would expect 10Kohm. If you measure 10K, it also means the path from PB to SIO as well as R811 is likely OK.

**pingaroon** · 03-29-2021, 09:13 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Hi Spider, thanks for your assistance here.

I managed to find R811 by pure luck - it is to the bottom right of U51 (SIO).

I have 2 boards, one I'm trying to fix and another which is for parts only.

I got a reading of 10K ohms as per schematic on the other side of the resistor R811 on both boards.

I could only test for continuity between R811 and B67 on my broken board from which I had desoldered the SIO exposing the layer B pins (it beeped).

Since R811 is literally right next to the SIO and the board looks physically very good, I would imagine there is continuity between R811 and pin B67. The problem is that B67 is not exposed on this chip - the only way to test would be to remove the chip, which I would rather not do again if at all possible.

Do you think that I need to do that anyway, just to absolutely confirm the path from the power button to B67 is good?

I think the problem may be that the SIO is refusing to start the board because of some other problem.

I still don't know why the voltage from the bios chip should be anywhere near the power button - normally the 3.3v comes from board power supply, not the bios chip?!! Also weird is the board starts EVERY time when plugged in even when the bios settings are saved when it should remain off.

Please see attached for summary

Any advice on what to do next? Many thanks

Attached Files

**pingaroon** · 03-29-2021, 11:28 AM

Re: Dell E6540 starts with Jack, but not with Power Button

**In previous post I meant "CMOS Battery", not "bios chip"

**mcplslg123** · 03-29-2021, 11:07 PM

Re: Dell E6540 starts with Jack, but not with Power Button

The board getting on every time on adapter even when cmos battery is good--a clear sign of RTC section failure. I highlighted this in post#3 but perhaps you choose to ignore it. On page 15, RTC section is described. You need to check RTCRST#,SRTCRST#,INTVRMEN(Internal VRM Enable),INTRUDER#+PCH_DCPRTC and PD3 Voltage on all pins. You can check RTCRST# on CMOS1 Jumper as well.

PS: PowerSW is powered by RTC CELL, so the voltage on power switch is not from bios chip. Read the schematic carefully.

**pingaroon** · 03-30-2021, 02:22 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Certainly not ignored, MCP, I just don't have the experience.

I have been self-teaching by watching videos, but have never encountered a problem such as this. So information such as "RTC section failure" may be 100% accurate, but leaves me unable to proceed as I am so new to this. I can change chips and reflow, and find shorts, but I am looking to go to the next level.

I will look at the information you provided in your post and see if I can work it out. Interpreting schematics for me is completely new, and I have zero electronics background.

I am very grateful to all those like yourself who take their time to help novices like myself, especially those who do this professionally, so hats off to you

**mcplslg123** · 03-30-2021, 06:19 AM

Re: Dell E6540 starts with Jack, but not with Power Button

ok@pingaroon. Lets begin with measurement at CMOS1 Jumper which should be close to ram slot.

**Spider1211** · 03-30-2021, 09:06 AM

Re: Dell E6540 starts with Jack, but not with Power Button

@mcplslg123; even with RTC issue, shouldn't pressing the power button still have an effect on the system? Especially if its booting into windows?

@pingaroon, did you by any chance change the power button actions in windows to 'do nothing' when pressed? Does pressing and holding power button while OS is loaded turns it off?

**pingaroon** · 03-30-2021, 03:57 PM

Re: Dell E6540 starts with Jack, but not with Power Button

Hi, well I managed to track down the various parts of the RTC section on the board which I had to do painstakingly because there is no boardview and many of the components are not labelled. (I also today fixed another E6540 board which had a short, so at least I now have a working board to compare against) I think I learned a lot just by trying to make sense of the schematic, especially when I found which part they corresponded to on the board.

The output from PD3 (just next to the bios battery) is 2.7V

CMOS1 measures 2.7V (and the associated resistors and caps). (It was on the other side of the board from the RAM slots, directly behind the BGA chip UH1) The schematic is full of different chips UH1A, UH1B, UH1C etc which I can't find anywhere on the board. There is only UH1, the BGA chip, just above CMOS1. I wonder if UH1A, B , C etc refer to particular parts of UH1?? How can you test without removing the chip to expose the pins?? I can't resolder a BGA chip.

The other RTC section is near the audio chip (about an inch below the power button) and here is where I think I may be close to something. Page 30, R1084 measures 2.7V and 100ohms. This is in series with a dual mosfet Q327. The schematic suggests that 2 of the 6 pins should be ground and that is the case on my good board. HOWEVER, on the one I'm trying to fix the lower right pin is also shorted to ground. I removed the mosfet and the pin is still short to ground, so I put the mosfet back. That is as far as I have got today. If I can work out what is shorting that pin, perhaps that will solve this problem?

So thanks MPC, for the RTC information.

Spider, perhaps the power button not working is a product of the RTC problem? (Since the voltage from the RTC ends up on the PB by design) The PB does not register in any way with the board off, or booted into an o/s. I booted into linux and windows (no mods), but still the PB presses do not register either with a short or long hold press. I would know for certain if the PB presses are reaching the SIO only by once again desoldering the SIO to expose the pins, but I have a feeling it's the RTC fault causing the PB to not operate normally. What a head twister!!!!!

**mcplslg123** · 03-30-2021, 10:51 PM

Re: Dell E6540 starts with Jack, but not with Power Button

@SPIDER1211, Yes I agree with your views and that has to be tackled once RTC issue is resolved.
@Pingaroon, You mean pin3 of Q327 is shorted to GND?? If so, remove the audio codec and check again. The output from PD3 as well as voltage on CMOS1 jumper proves RTCRST# is present. No point in removing the BGA IC. Measure whatever you can without risking too much.

**pingaroon** · 03-31-2021, 04:07 AM

Re: Dell E6540 starts with Jack, but not with Power Button

Alas, a false alarm,

The working board also has this 6th pin shorted to ground when off (it is one of the drain pins, not sure which way round the component is).

https://cdn.badcaps-static.com/pdfs/...da66a0a8a8.pdf

SO, my working board, my spare-parts board and the board I am trying to fix are all identical with the CMOS voltage in all the areas I can see referenced in the schematic.

4 areas that I found:

- the output of PD3 right next to the cmos battery

- the pin CMOS1 and ME1 (other side behind the BGA chip UH1)

- the 2 resistors and 3 caps bottom right of the front side of UH1

- the resistor directly above the mosfet Q327 and the top left 2 pins of Q327 itself - next to the audio chip U74 under the power button

I was hoping I would find a difference between them, but they are identical on all 3 boards.

Is there anything else left to try?

Thanks

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Dell E6540 starts with Jack, but not with Power Button

Dell E6540 starts with Jack, but not with Power Button

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