Won't charge or turn on.

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Dell Latitude E6540

Haswell business laptop introduced by Dell in 2013. This system is notable for being the first Haswell business laptop released, but has multiple known problems - including AMD GPU failure. A new battery will operate the laptop for ~4-7 hours, depending which one is installed.

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Brandon Boulter @dragonbb83

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Postado: 6 de out de 2020

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Won't charge or turn on.

laptop charger led light goes off when plugged in to laptop and stays off until unplug from all. Laptop won't turn on at all on battery or ac. Tore it down to the motherboard and found an are with shorted capacitor. Trying to eliminate possibilities and found an ic chip that is grounded on three pins and these pins are also group to the capacitors. Below is a picture. Also found manufacturer but thats it. Need help find information on chip and where those pins go. Thank you for your time and support.

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Florian Schießl @ikoze Rep: 25 1 · Answer 1 · 2020-12-06T09:09:45-07:00

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Florian Schießl @ikoze

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Postado: 6 de dez de 2020

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Hi,

I recently got a notebook with the same problem. Thanks to your post, I got on the right track on fixing this. The pins you marked shouldn’t be grounded. Therefore, there had to be a short circuit somewhere. According to the schematics there should be the chargers voltage of 19V.

So I soldered a wire on these pins and connected my lab power supply. After feeding a current of 3A, I finally found a place which got hot. As it seems, the capacitors PC736 and PC734 were shorted. After removing them, the short was gone, the charger didn’t turn off again and the power LED on the board now flashes once every time I connect the charger.

I just ordered replacement 22uF 0805 25V capacitors. I’ll keep you posted.

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I just replaced these two capacitors. The notebook works again without problems. Charging is ok as well as power from AC or battery.

19 de dez de 2020 por Florian Schießl

@ikoze

Good work.

Were both of the capacitors shorted then?

Also probably just a typo but did you mean PC735 and not PC736? ;-)

Cheers

19 de dez de 2020 por jayeff

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jayeff @jayeff Rep: 448,9 mil 11 366 1,4 mil · Answer 2 · 2020-10-06T07:29:12-07:00

jayeff @jayeff

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Hi,

What is the board number of the motherboard? (printed on motherboard)

Try searching online for "(insert board number) schematics". Sometimes you can be lucky and find the schematics for the board which will have full details as to what each component is and how it is wired.

Also I believe that the IC is a 4835D P-Channel mosfet going by the markings on the IC

Here’s an image of the IC in the schematic (see p.68)

(click on image to enlarge for better viewing)

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Thats what i found too and I did Google the motherboard number and got a schematic for it still reviewing it. But can the fault be this if 3 pins are ground to the board and multiple capacitors, a fuse (which I remove and short is still there). Omhs reading on chip shows all every pin is connected to each other. Like o

Pin 1 is connected to pins 5, 6, 7 and 8. Same goes with pin 2, 3 and 4

6 de out de 2020 por Brandon Boulter

@Brandon Boulter

See image above for how it is wired.

Pins 1, 2 & 3 are connected to each other but not to pin 4 unless the IC was short circuit and also not to 5-8 unless the diode is faulty or you had the leads reversed when testing or the IC is short circuit. You may have to remove the IC from the board and test it out of circuit

This is the component that is shown in the circuit SI4835DDY-T1-GE3_SO8~D

6 de out de 2020 por jayeff

no I didn't and I had the negative lead on pin 4 when just testing ohms/continuity against other pins no power. Correct pins 1, 2 &3 are only connected to each other and pin 4 is by itself but however, pins 1, 2 &3 are also grounded to the board when i have my negative lead on a test pad.

6 de out de 2020 por Brandon Boulter

@dragonbb83

Bit confused as before you said that pins 1,2 & 3 were connected to pins 5-8 as was pin 4? See your 1st comment above i.e. "Pin 1 is connected to pins 5, 6, 7 and 8. Same goes with pin 2, 3 and 4"

IF the earth is a solid earth i.e. no resistance at all and is only on pins1-3, you will have to check from pin 1-3 to see where the earth is coming from. You will have to unsolder the capacitor PC700 pin 1 from the board and also the next IC pin 4 (can't see what it is designated in my image above) and then check.

If it is still there then you have to find where the +SDC_In connection goes to and start tracing it from there.

If it is not there then check the IC or the capacitor

If it is a resistive earth, even 1 Ohm,there may be a backfeed path through other components which connect to the IC which may be normal as it mightn't affect things when the power is connected. This has to be considered when testing for faults at component level.

6 de out de 2020 por jayeff

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Zach Mentz @zmentz Rep: 369 10 2 1 · Answer 3 · 2020-10-06T06:13:01-07:00

Zach Mentz @zmentz

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Two questions when you took apart the laptop did you unplug the battery before you unplugged anything else? and also if you have a multi meter see if it pulls anything at all or anything abscure. if you are able to find a schematics for the laptop and figure out what those all connect to ex. main power/display and so on. The capacitors themselves are eaisly replaceable if you know how to microsodder. But if you can tell me what that chip is called and everything its connected too i can do some further research and help out more

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Yes I unplugged the battery and held the power button down for 30sec to discharge any electricity left in the board before disassembly

6 de out de 2020 por Brandon Boulter

So I took a multi meter to see if I can get any readings. I started with one pin on onside and checked for ohms and all pins on opposite side of chip connect to every single pin. From Google 4835d I found that the mfn. Is vishay but thats it. Also found the mothboard schematic but could find chip on there. Found it on here https://www.alisaler.com/dell-latitude-e... chip location id is pq700 on page 68 4835d p-channel mosfet

6 de out de 2020 por Brandon Boulter

alright let me do some research and see what i can find out,

6 de out de 2020 por Zach Mentz

Thank you for helping. Im at a lost right now

6 de out de 2020 por Brandon Boulter

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Dell Latitude E6540

Won't charge or turn on.

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