Alienware 15 R3 Motherboard Issues Help Plz!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Nobody noticed? From measurements one of your DC-IN MOSFET is internal shorted sind ACDRV doesn't reach 25V. Should be easy to solve from here.

Okay so how do I determine which MOSFET it is? I've read the charging circuit sticky, and looked over the datasheet for the charge controller, sadly I just don't understand it enough to figure it out. I don't know which pins indicated to you that there is a shorted MOSFET, I am trying to figure it out on my own but I am just not seeing it.. Thanks for your time and interest! Could I get another hint perhaps? =)

[sikocan]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

PQ707, PQ701, PQ708, PQ702. With no power or battery check in resistance mode Gate to Source on all of them maybe.
See pic.

[sikocan]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Schematics if needed.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Okay I was just testing the mosfets in the area to see if any showed all pins shorted and pq701 has all pins shorted, is that my bad one then?

EDIT: I checked pq707 and pq702, they are on the other side of the board, and pq707 is also shorted all pins. So would that mean both are bad? Thank you guys so much!! I feel like I'm so close to having this solved! =D

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Just checking source to gate all 4 show source to gate shorted.. I'm checking pin 1 to 4, hopefully that's correct. I was trying to figure it out on my own before I saw the last couple posts..

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

How are you measuring the resistance?

Which scale on your meter is being used?

What are the exact meter readings?

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

How are you measuring the resistance?

Which scale on your meter is being used?

What are the exact meter readings?

I am just using auto range, if that's what you mean by scale?

pq701 0.3 Ohms
pq708 0.6 Ohms
pq707 0.2 Ohms
pq702 0.3 Ohms

These are pin 1 to pin 4

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Remove PQ702 and check if short is gone.

Then remove pq708 and check again if required.

Do not power up after removing the mosfet (s).

[sikocan]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

It's quite rare for so many Mosfets to be shorted. Gate which connects to BQ is probably fault at, let's see.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Should I not remove the MOSFET(s) then? I'll have to do it a little either way but I found all my equipment that I need I think.. It's been so long since I have used this stuff, anyone have any pointers to save me having to read up on how to do this stuff again? I just don't recall the preheat temps, the air nozzle temp and I'm wondering if I have to remove the plastic ac-in connector beside it or can I just shield it with some foil tape? Thanks!!

[piernov]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Gates are connected together so expected to have the same voltage on gate for all MOSFETs, and also show up on ACDRV.
PQ702/PQ708 are likely ok since current is flowing through body diode since they are not turned on (hence 0.6V drop).
Certainly a problem with PQ707/PQ701 since they are not turned on but still let current flow even though they are in reverse. They are in parallel so either or both could have a problem.
Schematics show 4.7 ohms resistor before gates of PQ707/701 so resistance measurement of PQ708/PQ702 are a bit surprising. Can be confirmed after isolating the issue with PQ707/PQ701.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Gates are connected together so expected to have the same voltage on gate for all MOSFETs, and also show up on ACDRV.
PQ702/PQ708 are likely ok since current is flowing through body diode since they are not turned on (hence 0.6V drop).
Certainly a problem with PQ707/PQ701 since they are not turned on but still let current flow even though they are in reverse. They are in parallel so either or both could have a problem.
Schematics show 4.7 ohms resistor before gates of PQ707/701 so resistance measurement of PQ708/PQ702 are a bit surprising. Can be confirmed after isolating the issue with PQ707/PQ701.

Okay I get it. I am back home now, I will get setup and pull one. Thank you!!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

I apologize, my girlfriend came over so I had to put everything away then set up again after she left.. I pulled pq702, now what would I test next? Ty!!

[sikocan]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Check the MOSFET outside, still sorted? Replace it.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Okay so this is a little bit frustrating.. The mosfets are marked with a circle on one side which I took as the indication that that was the side with pin 1. After removing the first mosfet looking at the bottom I can see that pin 1-4 are connected on the bottom side of the chip, so I don't know what's going on, it appears the chip is marked reversed. The mosfet isn't the same chip that the schematic showed being used for the mosfets but I looked at it's datasheet and it says the pinout is the same as the one the schematic shows but looking at the bottom of the chip pins 1-4 are clearly the drain. So I hope I don't have to put it back just to remeasure.. Anyway, retesting the resistance of the source to gates now that I know they are marked in reverse, and assuming they are all marked backwards, here's the results.

Pq702 - 5.8M Ohm (removed from board)
PQ707 - 12 Ohm
PQ708 - 6.6 Ohm
PQ701 - 2.1 Ohm

Should I put pq702 back?
Thanks guys.

EDIT - attached picture, the side with the big circle is not the side with pin 1.. 😕

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Ok. Just need to get your orientation correct for these parts.

When you review the datasheet -> place the component on your table and review the dimple or white dot which should be located to the TOP LEFT corner of the mosfet.

That is pin # 1.

Below it, still on the left is pin # 2 -> # 3 and # 4 (end).

Now counting in a 'U' shape, BOTTOM RIGHT side = pin # 5 -> # 6 -> # 7 -> #8 (TOP RIGHT of the mosfet).

ICs work and count in the same manner.

On these mosfets, pins 5-6-7-8 are all shorted together to allow for heavy currents to travel through the device = DRAIN pin cluster.

So back to 1-2-3 = grouped together = SOURCE pin cluster.

Only pin # 4 will be by itself = GATE.

Now, when you solder this back onto the PCB, locate the side of the PCB pattern that has pins 5-6-7-8 shorted together. Check it with your meter first.

You are placing the pins down and the datasheet has the 'superman x-ray view' so you are looking through the device to solder onto the board.

Hope this is clear.

If you are observing that this removed mosfet is NOT fixing the short, just make a note of it and proceed to remove another.

@Piernov mentioned above that he suspects the FIRST 2 pair should be reviewed for this shorted part.

Either way, my suggestion is to only draw a small diagram of which parts are where and make a note of the pin # 1 of each so you can solder them back. Also suggest to leave the parts off the board till you locate the short.

One mosfet can make this board look shorted.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Okay I think I understand. One other thing, I just noticed the two mosfets on the bottom of the board are different than the top ones, they seem to be dual mosfets, each has 2x D1, 2x D2, 2x S1, 2xS2, 2x G1, 2x G2.. These are the ones in the picture from my last post. This is a picture of the ones on the top side. By top side I mean the side with the cpu and gpu..

[sikocan]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Gate to source should measure in k ohms or higher.

Here is a good video
https://youtu.be/Xc_yIdHw0zI

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

So on the dual ones should I be checking g1-s1 and g2-s2?

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

The mosfets in the schematic are showing as singles. Confirm the white silk screen labels for each.

Make a note of which parts are linked to where on the PCB. These are common parts and from the schematic - each mosfet is the same for these 4 mosfets.

See attached which should clarify the pin # 1 and placement for the share pic.