Alienware 15 R3 Motherboard Issues Help Plz!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

This is what both the bottom ones are, maybe I'm not finding the right datasheet or something.. That's pq701 and pq708.

And yeah I see the tiny dimple now that marks pin 1.. That's annoying lol, I was looking for anything else like that I guess I just missed it. My eyes certainly aren't what they used to be.

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

See attached.

The datasheet for these mosfets has been posted in the earlier post.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

See attached.

The datasheet for these mosfets has been posted in the earlier post.

Okay lol that helps.. I was searching for 4803 mosfet.. Sorry I'm still learning obviously..

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Just to make sure I'm understanding, once I get the bad mosfet out the remaining ones will test high Ohms S-G in circuit? Thanks again! Sorry for all the questions, I just want to understand what I'm doing as much as possible..

And I took your advice and drew a simple diagram of the area and the pin 1 location. Lesson learned.

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Correct. For your logic board, there are 2 x mosfets that are working together and then follow another 2 x mosfets before the power rail is fed to the logic board.

As per @Piernov's articles, typically there are only 2 x mosfets (total) but the better designs, like yours, now feature 4 of them.

However, we believe that at least one of these 4 is defective.

More so, one the 2 mosfet boards, it is the 2nd mosfet (so it is not the one that is mated directly to the AC adapter) that goes bad. So for this reason, I suggested for you to remove this mosfet. You still have another mosfet on this same leg but @Piernov is suggesting your problem probably is in the first 2 x mosfets.

We are only trying to nail this down with the least amount of soldering but proceed as you wish.

Do not place back any of the mosfets till we determine which one is the bad boy.

After you no longer have the 0 ohm short condition, the last removed mosfet is the mosfet that is the suspect. Confirm it by checking the resistance of the removed mosfet while it is out of the circuit.

Check again, the resistance between source & drain pins, etc. while the mosfet is on your table. If the resistance is low, it is defective.

Once you can confirm it, you will need a replacement. We can work on that next. The mosfets are not difficult to source but we often use stores like Digikey. Mouser is another option but shipping to Canada is $20 from them.

DK will sell to anyone with overnight service @ $8 (shipping) + parts you wish to purchase. Best option. We can guide you once we can 100% confirm the mosfet is defective. Otherwise, you can order from Aliexpress which will be cheaper but the parts will not arrive for another 3-5 weeks.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Okay thanks for that, it helps to know I'm following.. As luck has it, I have my original (same) motherboard still, I was thinking I would just borrow one from that board if there's no reason I shouldn't? I'm just getting everything prepped again to pull another. Will post when I get a bad one off.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Alright I pulled pq707, it tested good, so I pulled pq701 next and it tests 3-60 Ohms between source and gate.. And the remaining mosfet (pq708) tests 255K Ohms source to gate. So how difficult are these going to be to solder back if I don't have any paste solder?

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

I pulled one from the donor board from location pq707.. It tests 14M Ohms S - G..

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Good. You do not need solder paste as there is enough solder remaining on the pads from where these parts were pulled.

However, you should have solder flux. You may be ok to proceed without it but flux just makes it easier to solder.

Keep the air pressure relatively low so that other nearby parts do not end up in the next province. Enough heat to have liquid solder. Go around in circles from the top side and the part should just sink back onto the pads like before.

As you solder each back, wait till the part is cool. Then check the resistance again on the logic board before moving to solder back the next mosfet.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Good. You do not need solder paste as there is enough solder remaining on the pads from where these parts were pulled.

However, you should have solder flux. You may be ok to proceed without it but flux just makes it easier to solder.

Keep the air pressure relatively low so that other nearby parts do not end up in the next province. Enough heat to have liquid solder. Go around in circles from the top side and the part should just sink back onto the pads like before.

As you solder each back, wait till the part is cool. Then check the resistance again on the logic board before moving to solder back the next mosfet.

Okay great, yeah I do have flux. And the desoldering braid I have seems to be beyond its best before date also, it doesnt want to suck up solder worth a damn... I'll try just reusing the old solder then. Thanks again!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

I got the first one replaced, but it doesn't look like it's lined up as perfectly as it was, should I worry about it it just move on? The S-G is still not shorted and the D-GND isn't shorted, I assume that would mean it's okay? Thx!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Okay last 2 are done also, is there anything else I should check before reassembling to test?

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Removed all the kapton and cleaned the board.. Should I just reassemble and cross my fingers at this point? =)

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

The soldering looks fine for these mosfets.

The pin pitch is not as delicate as smaller devices so there is some flexibility to solder these down.

Before powering up, check the resistance again like before to confirm there is no short.

Then power up and check.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

The soldering looks fine for these mosfets.

The pin pitch is not as delicate as smaller devices so there is some flexibility to solder these down.

Before powering up, check the resistance again like before to confirm there is no short.

Then power up and check.

Okay yes I already did check and lowest resistance is 255K Ohms source to gate.. I'll cross my fingers and reassemble in that case.. =))

[piernov]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

I got the first one replaced, but it doesn't look like it's lined up as perfectly as it was, should I worry about it it just move on? The S-G is still not shorted and the D-GND isn't shorted, I assume that would mean it's okay? Thx!

Looks like solder did no take properly on the pins. Remove MOSFET, put some fresh leaded solder on the pad, add flux and solder it back with hot air. To make the solder joints look even better, add flux again and go around the pins with a soldering iron.

When the MOSFET is not soldered properly, resistance will be higher and it'll warm up, and if the thermal pad is not soldered properly either the MOSFET will not be able to dissipate the heat to the power plane.

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Looks like solder did no take properly on the pins. Remove MOSFET, put some fresh leaded solder on the pad, add flux and solder it back with hot air. To make the solder joints look even better, add flux again and go around the pins with a soldering iron.

When the MOSFET is not soldered properly, resistance will be higher and it'll warm up, and if the thermal pad is not soldered properly either the MOSFET will not be able to dissipate the heat to the power plane.

I was thinking that could be an issue, I ordered some fresh braid/wick when it comes I'll fix it. In the meantime I'm so happy to report that the battery is charging and the computer seems to be 100% again! =D So I can't tell you all how much I appreciate your guidance, your all just so freakin awesome!! Thank you!!

[z32KRAzY]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

Could one of you guys possibly recommend a part from mouser or digikey that I could order to replace the one I took from my old board? It was labelled B04 N03.. I'll attach a picture of the chip for reference..

[mon2]

Re: Alienware 15 R3 Motherboard Issues Help Plz!

https://www.digikey.ca/en/products/d...TR2PBF/2639558

https://www.digikey.ca/en/products/d...4TRPBF/2639551

https://www.digikey.ca/en/products/d...5TRPBF/2639552