Dell Inspiron Mockingbird

[Eniaro]

My post may look weird if you are not logged in

MKB N TGL 8L MB
19861-1
KTKHP$JA

I need help with identifying a damaged part and a missing part.

Backstory

PC won't turn on and flashes a light code which =Power rail failure

I took it apart and saw this mess


Cleaned it in an ultrasonic cleaner



Current

Still gives an error code (Power rail failure)
Deeper dive into the same area found a damaged part and a missing part

I can't find the board view for this board and I'm learning to read schematics (which was posted here)

I'm unsure of what this is.

Markings on the chip is L26 B
Is it U7102?


AND what went missing?

[Eniaro]

Re: Dell Inspiron Mockingbird

I looked up a photo of the board, and it appears to be a missing resistor

If this is correct L26 B is a Linear voltage regulator IC
Can anyone confirm this is true?

[Eniaro]

Re: Dell Inspiron Mockingbird

For you

You Rock , Thank you


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According to the board view and schematic, the missing part is reference designator R7172 (0R2J-2-GP). I couldn't find 0R2J-2-GP on mouser or anywhere, so I used Bing's AI to have an understanding of the value of the resistor

0R2J-2-GP seems to be a part number for a resistor with 0.2 ohms resistance and 2% tolerance. It is used in various electronic circuits such as level shifters13, power regulators4, and LED drivers3. What are you looking for specifically?

The case code for 0R2J-2-GP resistor is GP212, which means it has a power rating of 0.25 W and a size of 0805 (inches) or 2012 (metric). The case code is usually printed on the resistor itself or on the packaging.

Based on the search results, some possible alternatives for a 0.2 ohm resistor are:

A through hole wirewound resistor with a power rating of 3 W and a voltage rating of 100 V1.
Two 1 ohm resistors or four 2 ohm resistors connected in parallel2.
A SMD chip resistor with a power rating of 500 mW and a voltage rating of 150 V3.
However, these alternatives may have different physical sizes, tolerances, temperature coefficients and other characteristics that may affect your circuit performance. You should always check the datasheets and specifications before replacing any component.

I take Bing's AI answers with a grain of salt as my very first use it gave me incorrect answers with correct answers in one line. I believe there is some truth to what it found however something may be wrong with the answers it provided, and I don't have the knowledge to fully decern what's true and false in this situation. However, what I could comprehend was that ERJ-U6SJR20V might be a candidate to replace 0R2J-2-GP

According to the datasheets1234, ERJ-U6SJR20V is a thick film resistor with a resistance value of 0.2 ohms, a power rating of 0.25 W, a tolerance of 5%, a package type of 0805 (2012 metric) and an anti-sulfur and AEC-Q200 qualification. These specifications seem to match those of 0R2J-2-GP, so it may be possible to use ERJ-U6SJR20V as a replacement. However, you should also consider other factors such as temperature coefficient, voltage coefficient, noise level and reliability before making a final decision.

Does anyone agree or have any viewpoints?
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The unknown damaged part is reference designator U7102 and can be purchased from Mouser yay.

I was giving up on this board but decided to patch fix U7102 and hoped that R7172 was not necessary. (Pin 4 is connected to the via and not the trace. It's an overhang that needs to be trimmed )



Plugged in and the light code changed from Power rail fail to 3 amber 5 white = "SMBIOS FLASH CORRUPTION"
Thanks to @chenwei there might be hope for this board

[reformatt]

Re: Dell Inspiron Mockingbird

U7102 is a TPS22975, which is a load switch. The marking would be 13XH, however L26 is for an equivalent device APL3526. Same function, just different manufacturer. Testing this should be straightforward. Vin/Vout and an enable. Also check continuity with a meter to elsewhere in the circuit using the boardview. Corrosion can damage via's that isn't often visible.

The resistor you mention based on the pads from the factory was no stuff. It's listed as DY, which is probably a different variant/model, and not stuffed.

[Eniaro]

Re: Dell Inspiron Mockingbird

reformatt you are 100% correct about R7172. After reinspecting the board I realized, I assumed there was a missing part because of the solder formation of 1 pad. the other pad has a perfect shape therefore nothing could have been there like you said

[Eniaro]

Re: Dell Inspiron Mockingbird

So I got U7102 part in and while removing U7102 I blew away

R7176 100KR1F-GP (I'm guessing this is a 100k 0402 Resistor?)
C7137 SC220P50V2KX-3DLGP
C7135 SC1U10V2KX-1DLGP
Can someone help me decode what the values are and point me in the right direction for replacement parts


How did this happen?
I didn't realize my Quick 861dw from the factory is set to °F most of my tools are from JBC tools with the exception of a nano iron and hot air station all of which are by default celsius except for the quick.
I don't use the hot air station a lot but for U7102 my solder wick trick doesn't work, so out came the hot air station which is set to 350°F obviously nothing melts
Then I glanced up and realized what was happening. I changed it to °C.
The Quick's air setting was the next thing... treating it like a JBC, I set it to 50% of its airflow which is 60, this is still way too much and this is where parts decide to exit before I noticed what was going on

[reformatt]

Re: Dell Inspiron Mockingbird

R7176 - 100K
C7137 - 1uF 10V
C7135 - 220pf 50V

Size, whatever fits, prob 0201 for R7176/C7135 and 0604 for 7137. Voltage ratings don't really matter all that much in this circuit.

[Eniaro]

Re: Dell Inspiron Mockingbird


Instead of ordering,
I have a Compal AAL15 LA-D071P board I might be able to harvest parts off.

LA-D071P R2711 (100KR2J-1-GP) --> MOCKINGBIRD_TGL R7176 100KR1F-GP
LA-D071P C2607 (SC2200P50V2KX-) --> MOCKINGBIRD_TGL C7137 SC220P50V2KX-3DLGP
LA-D071P C2704 (SC1U10V2KX-1GP) --> MOCKINGBIRD_TGL C7135 SC1U10V2KX-1DLGP

[SMDFlea]

Re: Dell Inspiron Mockingbird

Check C2607 again

SC2200P50V2KX 2200 picofarads
SC220P50V2KX-3DLGP 220 picofarads

[reformatt]

Re: Dell Inspiron Mockingbird

EC6102 or EC6103 if they are the right size. Should be heaps of 1uf caps on that board, in addition to 100k. Just need to be the right size.

Edit: Sorry all instances of 220pf are no stuff on this board. I'll take a look at the datasheet to see if this value is critical or not.

[Eniaro]

Re: Dell Inspiron Mockingbird

Check C2607 again

SC2200P50V2KX 2200 picofarads
SC220P50V2KX-3DLGP 220 picofarads

Thanks for catching that

PC617 (220P_0402_50V7K) maybe?

[Eniaro]

Re: Dell Inspiron Mockingbird

EC6102 or EC6103 if they are the right size. Should be heaps of 1uf caps on that board, in addition to 100k. Just need to be the right size.

All missing from this board No dGPU

[reformatt]

Re: Dell Inspiron Mockingbird

On the datasheet for TPS22975, Ct sets the slew rate for switching. For 3.3V, it's 330us for 220pf, 105us for 0 (open circuit). So don't believe it will make that much of a difference if you leave it out. You can get the cap later if you think its creating an issue (or steal it from somewhere else on the board where it's being used for HF decoupling).