XBox One S - No Power On - Missing 3.3V

[LiftedTrace]

Hello all, I am at it again. This time a friend of mine came to me with a dead xbox. I figured, its already dead why not poke around and see if I can find out why.
Im new to this stuff and would like your input on if what I am thinking is correct.
I started by checking if the main + and - were shorted, and they were not.
I plugged in 12V to the main and started checking voltages at the test points. I have the 12V and 5V but not the 3.3V.
The main 3.3V comes from the 12V it seems from what I show in the pictures. I am getting .8V on the output of the coil. SO i was thinking, maybe something is shorted, dropping the 3.3 down to .8, so I decided to put 3.3V directly on the test point to check if the voltage got pulled down, and it did not, and drew very little current.
Seen as there is not much around this area, I was suspecting this little chip is not working as expected and not producing its 3.3V.

Your thoughts?
I also have no clue what this chip is, I cannot find any info on it to really test further.
Anyone have any direction I can go?

[fzabkar]

NB671GQ, Monolithic Power, Synchronous Step-down Converter, 5V - 24Vin, 6A, marking AEAy, QFN-16:
http://www.mouser.com/ds/2/277/NB671_r1.04-371602.pdf

Check the Enable pin to see whether the IC is being switched on.

[LiftedTrace]

Awesome, Thank you.
I checked the enable pin and its low (.09V). So now I just have to try and find what is supplying that voltage. I have no clue where its coming from and it very quickly vanishes thru the board. 
Looks like I have a nice hunt on my hands.
I'm half tempted to open mine up and take some reference measurements.
I'm afraid it might be coming from one of the main chips and if thats dead, maybe thats why its not enabling the 3.3V

[fzabkar]

Could we see a photo of the whole PCB?

[LiftedTrace]

Absolutely. Here is the front and back. If you would like higher res, let me know. This is as good as my phone takes.
I marked the chip that provides the 3.3 with a red X....upper left side of the board on the front.

[LiftedTrace]

I poked around the near by power supplies with the continuity mode, trying to poke everything I seen to try and find where that enable trace is going off to, but I didn't find anything.

[fzabkar]

Does the IC get a proper Vin supply?

I would measure the voltages at the large electrolytic capacitors, both leaded and surface mounted. Also measure the voltages at the inductors (Lnnn). These will be the inputs and outputs of the various switchmode regulators.

Also check the fuses, eg RT3F1, RT6B1, RT6B2. These have a Littelfuse logo (Lf).

There are several 5-pin chips which look like linear regulators or maybe load switches, eg U5D2 and two others near the bottom left edge of the PCB. Can you measure their inputs and outputs? Can you identify their part markings?

[fzabkar]

I though this thread looked familiar ...

https://www.eevblog.com/forum/repair/xbox-one-s-repair-(ebay-project)/

[LiftedTrace]

Yeah that was my failed attempt at trying to repair an ebay item. It was a lost cause. This one of my friends my be a lost cause too.

[fzabkar]

If you want to keep plugging away, we'll see how far we get this time.

[LiftedTrace]

Ok so, The Vin on the suspect chip is a solid 12V. The enable pin is not getting its voltage and I do not know where its coming from yet.
U5D2 looks to be getting its input from the output of the large coil next to the chip with the red X on top (the chip not getting its enable voltage)
U5D2 has no output voltage.
The two identical 5pin chips in the lower left also get their input from the large coil next to the red marked chip. These also have no output on them.
There is a dead short between the output of the coil and the inputs of those chips. I gave the 3.3v test point a low limited current 3.3v and I didn't see any drop in voltage, so I don't think something on the 3.3v side is pulling it down.

Oh and all the fuses checked out good.
This site: https://www.electronicproducts.com/Xbox_One-whatsinside_text-158.aspx
Was pretty helpful in finding some stuff, like them lower left 5 pin chips.
These chips were marked with: P6243WG and that site lists its part number as CAT6243DCADJ?RKG
Chip labeled U5D2 has marking of GK1DQ828 and I cannot find any info on this, but I assumed the input was the pin with the same voltages as the inputs on the other two chips and what the large coil was outputting.

[LiftedTrace]

If you want to keep plugging away, we'll see how far we get this time.

I enjoy this, Ill  until all options are exhausted 

[fzabkar]

That's a great teardown.

P6243WG is an adjustable linear regulator with an Enable pin (1). If there is no Vin, I would think that the Enables would be inactive, too.

I think if you continue on this path and map out the relationships between each of the supplies, then you can build a picture of the power layout for the PCB. Clearly there must be a main supply which powers whichever chip is responsible for enabling the NB671GQ. Maybe you will find other regulators with missing enables, and this may then give us a better idea of the source.

Just keep measuring the coils and large capacitors.

Edit:

U5D2 is an LDF adjustable regulator. Pin #1 is the enable.

LDF, STMicroelectronics, adjustable LDO regulator, 1A, 2.6V - 16Vin, PPAK-5:
pdf.datasheetcatalog.com/datasheets/stmicroelectronics/LDF_LDFPT-TR_LDFPVR_LDF33PT-TR_to_LDF25PT-TR.pdf

CAT6243DCADJ-RKG, ON Semiconductor, LDO Regulator, Adjustable, 1A, 2%, marking P6243WG, DPAK-5:
https://www.onsemi.cn/pub/Collateral/CAT6243-D.PDF

[LiftedTrace]

Do you think it possible these have the same enable inputs? I i remember correctly, the P6243 didnt have anything on the enable either. I just ignored it cause the Vin was gone too.

[fzabkar]

It would be helpful to know the state of Vin and Enable for each of the regulators. You will find additional switchmode regulators alongside the coils.

[LiftedTrace]

It would be helpful to know the state of Vin and Enable for each of the regulators. You will find additional switchmode regulators alongside the coils.

Ill take some readings and document as much as I find. It might be a few days with Thanksgiving coming up and long work days. Il post back as soon as I can.

[fzabkar]

If you can write up the markings on the chips, I can produce a BOM for you. Then you'll have something to work with.

[LiftedTrace]

Ill take a higher res image and jot down the voltages on the image. any un readable chips, Ill type in over them. Might take me a few days.
Thanks for the help.

[LiftedTrace]

Here is a link to a higher res image: https://www.dropbox.com/s/db9q1sntkaq0whq/XBOX%20Front%20Voltages.jpg?dl=0
I took a few measurements and put them on the chips.  The font is very small, about the size of the chip leads them selves. You need to zoom all the way in to see them good.
I didnt measure the 3.3V  chip ( not sure why I didnt do that one first  )
I find it very strange the EN pin doesnt seem to have any input to it. I cannot find where it goes.
The chip itself is getting 12V supplied to it though.
I am half tempted to take a resistor and tap off the 12V rail and see if I can even get the chip to turn on and output 3.3 manually.

[fzabkar]

Here is the BOM so far:

LDF, STMicroelectronics, adjustable LDO regulator, 1A, 2.6V - 16Vin, PPAK-5:
pdf.datasheetcatalog.com/datasheets/stmicroelectronics/LDF_LDFPT-TR_LDFPVR_LDF33PT-TR_to_LDF25PT-TR.pdf

CAT6243DCADJ-RKG, ON Semiconductor, LDO Regulator, Adjustable, 1A, 2%, marking P6243WG, DPAK-5:
https://www.onsemi.cn/pub/Collateral/CAT6243-D.PDF

LM339A, Texas Instruments, precision quad differential comparator, 2V - 36V, +/-1V - +/-18V, marking L339A, SOIC-14:
http://www.ti.com/lit/gpn/lm339a

TPS51916, Texas Instruments, Complete DDR2, DDR3, DDR3L and DDR4 Memory Power Solution Synchronous Buck Controller, 2-A LDO, Buffered Reference, 3V - 28Vin, 0.7V - 1.8Vout, QFN-20:
http://www.ti.com/lit/gpn/tps51916

TPS53819A, Texas Instruments, 3V - 28V Input, 40A, Eco-Mode, D-CAP2 Synchronous Buck Controller with PMBus, marking 3819A, QFN-16:
http://www.ti.com/lit/gpn/tps53819a

SN75DP159, Texas Instruments, 6-Gbps AC-Coupled TMDS to HDMI Level Shifter Retimer, marking 75DP159, WQFN-40:
http://www.ti.com/lit/gpn/sn75dp159

NT5CB256M16EP-FL, Nanya, DDR3 SDRAM, 4Gb x 16, 1.5V, 2133Mbps, BGA-96:
https://www.nanya.com/en/Product/3994/NT5CB256M16EP-FL
https://dl.khadas.com/Hardware/VIM1/Datasheet/Amlogic_STB_Release_V3.3_QPL20170609-Wesion.pdf

AON7403, Alpha and Omega, P-ch MOSFET, -30V, -29A, 18mOhm Rdson, marking 7403, DFN-8:
http://www.aosmd.com/res/data_sheets/AON7403.pdf

KLM8G1GEME, Samsung, eMMC, 8GB, 64Git x 1:
https://www.samsung.com/semiconductor/global.semi/file/resource/2017/11/Samsung_eMMC_2013-0.pdf

THGBMFG6C1LBAIL, Toshiba, eMMC NAND Flash, 8GB, 1 x 64Gbit, 3.3V / 1.8V, BGA-153:
https://www.es.co.th/Schemetic/PDF/THGBMFG6C1LBAIL.PDF

NTMFS4C55N, ON Semiconductor, N-ch Power MOSFET, 30V, 78A, 3.4mOhm Rdson, marking 4C55N, SO-8:
https://media.digikey.com/pdf/Data%20Sheets/ON%20Semiconductor%20PDFs/NTMFS4C55N.PDF

1812L150/24, Littelfuse, Polyfuse, 24V, 1.5A, marking LF150-24:
http://www.littelfuse.com/products/resettable-ptcs/~/media/Electronics/Datasheets/Resettable_PTCs/Littelfuse_PTC_1812L_Datasheet.pdf.pdf

AP2127K-ADJTRG1, Diodes Inc, 300mA HIGH SPEED, EXTREMELY LOW NOISE CMOS LDO REGULATOR, marking GEH, SOT23-5:
https://www.diodes.com/assets/Datasheets/AP2127.pdf

PMBT2222A, NXP, NPN transistor, 40V, 600mA, marking W1P, SOT23-3:
https://assets.nexperia.com/documents/data-sheet/PMBT2222_PMBT2222A.pdf

SSM3K324R, Toshiba, n-ch MOSFET, 30V, 4A, 1W, 56mOhm Rdson, marking KFD, SOT23-3F:
https://media.digikey.com/pdf/Data%20Sheets/Toshiba%20PDFs/SSM3K324R.pdf

SSM3J331R, Toshiba, p-ch MOSFET, -20V, -4A, 55mOhm Rdson, marking KFO, SOT23-3F:
https://toshiba.semicon-storage.com/info/docget.jsp?did=13019&prodName=SSM3J331R

NCP5901BMNTBG, ON Semiconductor, dual MOSFET gate driver, marking AZx, DFN-8
http://www.onsemi.cn/pub_link/Collateral/NCP5901B-D.PDF

SP1004U-ULC-04UTG, Littelfuse, TVS Diode Array, 0.20pF, 20kV, 9.2V clamping, marking 4C, 1004 DFN:
https://www.littelfuse.com/~/media/electronics/datasheets/tvs_diode_arrays/littelfuse_tvs_diode_array_ultra_low_capacitance_diode_arrays_datasheet.pdf.pdf

B130LAW-7-F, Diodes Inc, Schottky rectifier, 30V, 1A, marking SX, SOD123:
http://www.diodes.com/datasheets/ds30308.pdf

MP8757, Monolithic Power, Synchronous Step-Down Converter, 7A, 5V - 18Vin, marking MPyw + 8757, stepdown converter, QFN-21:
https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP8757/document_id/905/

TPS51206, Texas Instruments, 2A Peak Sink/Source DDR Termination Regulator with VTTREF Buffered Reference for DDR2/3/3L/4, marking 1206, WSON-10:
http://www.ti.com/lit/gpn/tps51206

SN74LVC1G08DBVR, Texas Instruments, single 2-Input AND Gate, 1.65V - 5.5Vin, marking C08F, SOT-23-5:
http://www.ti.com/lit/ds/symlink/sn74lvc1g08.pdf

NB671GQ, Monolithic Power, Synchronous Step-down Converter, 5V - 24Vin, 6A, marking AEAy, QFN-16:
http://www.mouser.com/ds/2/277/NB671_r1.04-371602.pdf

MP2161GJ, Monolithic Power, Synchronous Step Down Switcher, 2A, 2.5V - 6Vin, 1.5MHz, 17uA IQ, marking AEBy, TSOT23-8:
https://www.monolithicpower.com/en/documentview/productdocument/index/version/2/document_type/Datasheet/lang/en/sku/MP2161/document_id/450

RT5785AGJ8F, Richtek, synchronous step-down DC-DC converter, 2A, 2.5V - 6Vin, 25uA IQ, marking ON=, TSOT-23-8:
https://www.richtek.com/assets/product_file/RT5785A=RT5785B/DS5785AB-02.pdf

[fzabkar]

UC43 appears to be configured as a 5V regulator. There is a "5P0" test point below capacitor C4D1. ISTM that this part of the circuit is working correctly.

As for the chip's identity, all I know is that it is a stepdown converter made by Monolithic Power.

[LiftedTrace]

Yes the 5v seems to be working as expected.
I also have the 1.1STBY.
Anything that seems to get its main power from that 3.3V is shut down.
Now here is a question.
U4C2 turns on with a high EN. The data sheet says over 1v with a max of 12.
It’s currently got .2v.
So if the chip is off, how is it producing .8v on the coil L5C1?
I would think L5C1 should be 0v just the the others that are not currently on.

[fzabkar]

I can't understand why there is 0.8V there, either.

I notice that the Vout (pin 5) of U3D6 is low. Is something shorting its output to ground, or is the IC faulty? BTW, I don't see any feedback resistors on pin 4 (ADJ). Perhaps they are on the other side of the PCB?

It might help to compare this PCB with your water damaged one. A similar hires photo could help us to identify the date and batch codes from the part markings.

Edit:

FWIW, page 3 of the Xbox 360 circuit diagrams shows the reset logic for that PCB. Many of the power enables come from its Southbridge, so I'm guessing that the X861949-007 (Microsoft XBOX ONE ASIC) may be the source in our case.

https://elektrotanya.com/xbox_360_xenon_retail_rev_k7_fab_k_sch.pdf/download.html

Edit 2:

It may be obvious to some, but the circuit references include the PCB coordinates. I just worked it out now (doh!).

The PCB is laid out in a grid consisting of columns numbered from 3 to 9 running from left to right, and rows from B to G running from top to bottom.

A part is identified as type-column-row-number.

For example, C5E10 is a capacitor, C10, located at column 5, row E.

[LiftedTrace]

It may be obvious to some, but the circuit references include the PCB coordinates. I just worked it out now (doh!).

I had no idea, that's great for pointing that out. Makes for finding things much nicer.

So I just spent some time looking thru that xbox break down site and trying to find what ever chip U3d5 was, and the only thing I found was TPS206x in the DVB package. This lists the Output as Pin 1 and the input as Pin 5. I dont think this is the correct chip because I got almost nothing on the input, but almost 5V on the output.

I also cannot find out what U4D4 is from that site either.
As for the feed back resistors for U3D6, there are two resistors on the back side in very close proximity to the power supply package of components.
I am not sure this is where the problem is though, only for the fact that the small coil near all this it outputting 1.136V, and there is a test point right by there labeled TP1P1STBY which has 1.136V on it. Also very close to that is the test point for the 1.8V labeled 1P8STBY (Location TP4D4) which is reporting only .089V. Now Im no expert at this, but if this is a STBY voltage coming from some power supply, should I be reading 1.5_Ohms between this TestPoint and ground?

So, I cannot seem to find out where this 3.3V chips EN is coming from which makes me think it may be coming from the big kahuna (U4D2 ) The Xbox One chip. It may be possible that the 1.8V supply is shorted somewhere and the main chips knows it and is not allowing the rest of the machine to power up. If that is the case, How could I find out what is shorted? And is it possible its the main Xbox One chip itself which is shorted?

Maybe its time to give the 1.8V a current limited 1.8V on its testpoint and see what gets warm?

EDIT:
Ok, so I got impatient, I went ahead and gave that 1.8V test point the voltage it was wanting, with a 100ma limited current. There was absolutely no drop in voltage when I gave it 1.8V, and I cant seem to find where its coming from because when I check with Ohms, its virtually a short.
I seem to be stuck.

EDIT 2:
So I connected main power again and now I have 1.8V , and when I measure the resistance (power off) I get 71_Ohms.
How is this possible? Go from a dead short, to 71 Ohms?

EDIT 3:
The 1.8V seems to be coming from U3D6, the one you were saying the Output (pin 5) was a bit low.....its no longer sub .1, but 1.8, and pin 4 is also now at .8v 
Maybe my hitting the test point with 1.8V scared it straight?

The 3.3V is still out of commission though.

EDIT 4:
Ok so I decided to pullup the enable pin on the 3.3V power supply and see if it kicked on....and it did! 
But none of the others started working, because they also are missing their enables.
I dont know, I am really leaning towards the main Xbox chip being gone. None of the enables are tied together, so they must be getting their input from some control chip. and since there really is not much other than the large XBox chip and some power supplies, I am not sure what more I can do for this thing.
I could Frankenstein the thing and force all the chips to turn on by pulling up all their enables.....just to see if it boots, but not sure its worth it. 

[fzabkar]

I don't think it is a good idea to backfeed the supply voltage into the outputs of your regulators.

Have you checked all the other supply test points? Is your 3.3V supply the only one that is missing now? I suspect that the 1.5 ohm short may have been due to an MLCC (ceramic cap).