Dell Precision M3800 won't turn on

[mon2]

Re: Dell Precision M3800 won't turn on

When the laptop turns ON, do you see any graphics and does the display have the backlight, etc. ?

[TopPop]

Re: Dell Precision M3800 won't turn on

I put the motherboard back and reconnected everything except the battery. I see no graphics and no backlight. I press the power button, the light in the button comes on for about 4 seconds, and then it switches off. I've just been watching some videos and Googling some stuff. I guess the super IO chip is going through its component checks and finding something isn't good to go and switching off. I was looking at page 62 of the schematic specifically [AC in] 8th line down PBTN_SW# ...... 1ns < Tg < 4s Am I correct in thinking that everything before PBTN_SW# is working OK and something after that is not working?

[TopPop]

Re: Dell Precision M3800 won't turn on

I was probing around QV29 and QV30 and saw a messed up capacitor nearby. See attached photo. It is CT44.

[mon2]

Re: Dell Precision M3800 won't turn on

Apply flux and use low air pressure on this area. Apply the heat from the topside of the cap. Allow for the flux to trigger and the cap will swim back onto it's pads. Test again after this repair.

[TopPop]

Re: Dell Precision M3800 won't turn on

I guess I somehow caused this damage while taking the board out and putting it back so many times. Looking at it, I think one pad is still in place on the board and the other pad pulled up with the capacitor but is still holding on to the board on one end and that is what is still holding the capacitor where I found it. Could I just solder it to pins 2 & 3 of U4? I'm going to check the connections of pins 2 & 3 just to be sure they are still connected to the things they are supposed to be connected to.

Edit: I just probed for continuity. I'm not sure how but that little capacitor seems to be still connected to everything!

[mon2]

Re: Dell Precision M3800 won't turn on

Post pics of what you are up against.

[TopPop]

Re: Dell Precision M3800 won't turn on

A couple more pics. I think that's the best I can do for quality.

Maybe I need to just gently push the cap pad back in to its spot, reflow the connection points, and then get some UV setting conformal coating to keep it in place.

Or, I have some spare 10uF 25V 0805 caps. I could put one running diagonally from pin 3 to CT44's pad that is still on the board.

[mon2]

Re: Dell Precision M3800 won't turn on

You will need to apply ample flux. I read on a PCB website that even vaseline will work as a flux for soldering.

reference:

https://www.candorind.com/what-is-solder-flux-guide/
* see details in this article
* PS: We have used Candor in the past with excellent results. In our opinion, one of the best PCB shops in Canada.

After you apply the flux, be sure that your hot air tool is at least 350C (or higher) so that the flux activates and the solder on the PCB starts to melt. Only then, use your tweezers to shift this capacitor away from the IC and onto the pads where it belongs. When the heat is high enough, the capacitor will swim and move away with a gentle push. Be patient.

Use the solder in liquid state as a guide on when to nudge the capacitor.

Try again.

[TopPop]

Re: Dell Precision M3800 won't turn on

I got it back to where it belongs. See photo. Plus, I made sure there is continuity between the capacitor ends and pins 2 & 3 of U4 like there should be and I made sure I didn't short the capacitor somehow.

Though, that didn't fix the problem. I press the laptop power button and see a power light for about 4 seconds, no keyboard backlight and no screen backlight, and then the laptop switches itself off.

[mon2]

Re: Dell Precision M3800 won't turn on

It is a Dell.

Is the power adapter the original and recommended one for this laptop?

What is the voltage to ground of the PS_ID on the adapter connector?

Also confirm the same on the EC side, the same pin.

[TopPop]

Re: Dell Precision M3800 won't turn on

The AC adapter I have probably isn't the original but it is one that is compatible with this laptop. I have another M3800 that is in a better working state than the one I've been working on. This second one reports that the battery has permanently failed. It has adapter warnings enabled in the BIOS setup and doesn't complain about the AC adapter. It boots in to Windows. I've ordered a battery replacement for this one. Should arrive early next week. Basically, I've tried this AC adapter with another M3800 and it seems to work though I admit I will feel more sure about that after I get the replacement battery and see it charging.

The laptop I've been working on:
Pin 4 of ADP100 shows 3.32V
Pin 2 of PR102 which is connected to the ENE KB9012BF A4 chip which I think is the EC you referred to shows 3.32V
Looks like you have me checking to be sure that there is no problem with the line of communication between the AC adapter and the embedded controller.

[TopPop]

Re: Dell Precision M3800 won't turn on

I got the replacement battery. The other working M3800 has no issues with the AC adapter that I've been using with the broken M3800. It charges the battery too. The problem with the non-working M3800 is not the AC adapter.

[TopPop]

Re: Dell Precision M3800 won't turn on

I know I have +3VALW and +5VALW but I'm missing any fan activity and no screen graphics or backlight when the power button is pushed. I was looking at page 51 of the schematics. So I thought maybe I am missing +3VS and +5VS. I went looking for QZ8 but found that was removed and replaced by TI TPS22966 and some other components were added in as stated on page 50.

I went to page 34 and saw UZ4 also known as TPS22966. On the board it has +5VALW and +3VALW going to it but when I press the power button there is no +5VS and +3VS going out. Might I be missing PM_SLP_S3# which is causing UZ4 to not turn on? I checked pins 3 and 5 after pressing the power button and saw nothing on the meter. Interestingly, the pins are so tiny that I accidentally connected pins 3 and 5 to the neighboring VALW pins when I was trying to get a reading and the fans turned on so it seems UZ4 works.

I went back to page 62 and looked at the Discrete Power On Sequence.
T6 PCH_RSMRST# To AC_PRESENT showed 3.3V. Next I tried pressing the power button and checking T8 PM_SLP_S5# To PM_SLP_S4# (T41 to T42 on the board) and found no volts there.

[TopPop]

Re: Dell Precision M3800 won't turn on

So after some more checking I found the laptop will now charge a battery from the AC adapter, will run off the battery, will run with the battery and AC adapter plugged in, but will not run from only the AC adapter. With only the AC adapter connected for power, if I press the power button, the light in the button turns on for about 4 seconds and then shuts off.

PQ102 was suspicious. It had 13.5V on the drain, source, and gate and the body diode seemed to be bad. I replaced it. However, that did not fix the problem of the laptop not running from only the AC adapter so there is still something else I haven't figured out yet. It seems as if the board is determining the AC power is OK for charging the battery but isn't OK for running the laptop.

Any suggestions for where to look?

[TopPop]

Re: Dell Precision M3800 won't turn on

Unfortunately something new went wrong. I no longer have +3VALW and +5VALW

[4mc]

Re: Dell Precision M3800 won't turn on

I came here to see if you'd found a solution to this? I can't begin to understand any of this, even though I was once the Chief Software guy at Dell. Yep.

There are dozens of threads about this problem on dell.com - My m3800 which I bought with my employee discount when I left, has worked fine for 6-years, I have two genuine power supplies for, suddenly developed this problem.

I took it to a local guy, he said he got it booted, I approved replacing the battery and the fan, cost $162. It's still a great machine, 4x Core Intel i7 32GB RAM, 15 1/2 touch screen etc. It's such a shame for these to become ewaste.

Mine switched on last-night, I did an image copy of the SSD, it wouldn't switch on this morning. Sure I can take it back to the local guy and he'll no doubt recommend a new motherboard...

So, can't help, but really interested in if you can solve this...
here is my thread on dell.com https://www.dell.com/community/Preci...ht/true#M12305

++Mark.

[Sephir0th]

Re: Dell Precision M3800 won't turn on

So after some more checking I found the laptop will now charge a battery from the AC adapter, will run off the battery, will run with the battery and AC adapter plugged in, but will not run from only the AC adapter. With only the AC adapter connected for power, if I press the power button, the light in the button turns on for about 4 seconds and then shuts off.

PQ102 was suspicious. It had 13.5V on the drain, source, and gate and the body diode seemed to be bad. I replaced it. However, that did not fix the problem of the laptop not running from only the AC adapter so there is still something else I haven't figured out yet. It seems as if the board is determining the AC power is OK for charging the battery but isn't OK for running the laptop.

Any suggestions for where to look?

Since i understood it like that, that the board does work from battery but not from charger (otherwise clarify pls!), you have to look at charging controller again, especially VCC, ACDET, ACOK and ACDRV with charger only.

Did you solved the issue around +3VALW/+5VALW already?

[TopPop]

Re: Dell Precision M3800 won't turn on

Since i understood it like that, that the board does work from battery but not from charger (otherwise clarify pls!), you have to look at charging controller again, especially VCC, ACDET, ACOK and ACDRV with charger only.

Did you solved the issue around +3VALW/+5VALW already?

Hey, thanks for replying! Not sure why but I didn't get an email when you replied.

PU300 died for some reason. It was weirdly hot. That took out +3VALW and +5VALW. Got a replacement IC and put it on the board and now +3VALW and +5VALW are back. I checked that by checking the voltages from PL300 to ground and PL301 to ground.

Prior to PU300 dying I had the laptop running off the battery without the charger. If I had the battery and charger plugged in then the laptop ran and charged the battery. The only thing it wouldn't do was run with only the charger for power.

Now that PU300 is replaced I'm back at the point of pressing the power button, the power light comes on for about 4 seconds, and then the light and board shuts off. Yes, this is happening while using only the charger for power.

Unfortunately now the charger is not recognized by the board and no longer charges the battery. I checked this by going in to the Dell diagnostics while running off the battery with the charger plugged in. So, there are some more things not working.

I reflowed the pads for PU200 because I've been probing them a bit too hard and some of them looked like they might be bridged, they are so tiny. However, that didn't change anything.

[TopPop]

Re: Dell Precision M3800 won't turn on

Readings taken with charger only for power.

VCC is 2.9V
ACDET is 2.7V
ACOK is 0V
ACDRV is 0V

So with nothing coming out of PU200 on ACDRV the PQ200 and PQ201 mosfets don't do their thing. Do I have that correct?

[Sephir0th]

Re: Dell Precision M3800 won't turn on

Yeah, that's true but it still isn't clear for whether the board is fully working from battery. I mean, you can reach Windows and work normally with this device.

The answer tells whether this is just a symptom or the cause of your problem.