Surface Pro 7 1866 won't turn on...

[titomno2]

Hi guys,
Just have a surface tablet pro 7 (type 1866) with motherboard JALAMA_ICL_MB DV:2.0.
Can't power on the surface tablet, no reaction on the button whatever the charger (working) is plugged in or not.
After dissassembly I made a physical inspection without seeing any damaged component (nothing visible at least).

Made measurement:
With battery (low voltage 7.9V) the led D7013 is on (red)
Charging seems odd and decided to let it apart and working only with DC input.

With power supply 15VDC (white light on the charging cable).
D7013 is red
L5501 3V3 is measured at 3.284V => OK
U5904 +5VSB_VIN is measured at 6.171V => a bit high ?
+5VSB_PWR_ON measured at 0V => don't know if it is normal
PWRBTN1V8 measured at 2.8V => should it be 1.8V or 3.3V?
+1P8V_SAM measured at 1.798V (but nothing on pin 8 of the UEFI)
+5VSB measured at 11mV => so nothing

With USB-C power supply (without the 15VDC power supply)
The metter indicate 19.8VDC and 0.010A (sometimes 0 and when pushing the button it go to 0.010A then nothing)
Under thermal camera the TPS65987SD is slightly warmer than any other component.
Voltage on EXT_DC_IN is dropping to 0V and no light on D7013.

So far
It seems that there is something wrong with the TPS but can't figure exactly what is wrong.
Nothing heating up (expect the TPS but under 19.8V and 0.010A it is nothing).

Any Idea on what measure to find the culprit.

The tablette inside was in poor condition (disgusting is the appropriate word) but not find any liquid damage on the board which is clean and did not show any liquid damage and no remains of food.

Any help will be much appreciated (I'm a bit confuse on how dense is the material on such motherboard).

Best Regards,

[titomno2]

Finally the power button was the culprit.
With all information shared with mon2 I have learn enough to solve another issue on a second board.
If someone have the same issue he can test by shorting with a wire or metallic tweezer the pin 1 with ground.

Both boards are working.
Have a nice day guys.

[mon2]

U5904 +5VSB_VIN is measured at 6.171V => a bit high ?

This is VIN to the regulator so may be ok.

+5VSB measured at 11mV => so nothing

Remove all power. Measure the resistance to ground of this absent power rail +5VSB. What is the resistance in ohms? A low resistance may indicate a shorted part on the rail.

[titomno2]

I removed all the power.
Made the measurement on the port 2 of the coil and the result is strange!
It start at 500kOhms and decreasing rapidly to 10kOhms, go up again to 20kOhms and decrease again.
Did not see anything wrong on the bunch of capacitors just on the right

[mon2]

The resistance is high so no shorts here.

This absent rail is created by U5904.

What is the voltage to ground of the EN (enable) pin VSUS_+5VSB_ON?

[titomno2]

If you mean the Pin#15 (of the U5904) I have 0V when the DC is plugged led power on.
I read it from the capacitor C5919 as there nothing else related to this pin.
On the board the R5908, R5906 are not populated, only the C5919 is present and did not find short to ground (1.2MOhms without power supply).


Don't hesitate to ask me other measurement (it wil take time as I will be at work all the week).

[mon2]

This enable pin and others are being driven by a NXP ARM Cortex M4 microprocessor @ U3400D = LPC5400. Review the U3400D block of pins and confirm that this part is being powered. Test their voltage to ground.

[titomno2]

Hard for me but I think I have the information (the boardview and schematic are not easy to understand).
So measured voltage at pin 1 of the R3411 and read 1.788V so I assume VDD are OK.
Measured also SAM_RESET#R on C3419 pin 1 and read 1.783V so I assume RESETN is OK.

So I assume the NXP ARM Cortex M4 is powered.

It is quite painful to find area to check the value without touching the shield.

SL1_HPD2_EN = 0V
3P3V_HDP_EN = 3V
3P3V_HDP_VIN = 3.3V

[mon2]

See if this helps. The voltage to ground are listed for each inductor on this model.

The values in RED are diode mode measurements. Remove all power. Meter in DIODE mode. Red meter probe, yes red to ground. Black probe to the point to test.

[titomno2]

Very instructive. So with red probe on the ground and multimeter on diode mode here are the results:
Voltage Picture On my board
0.68V 500 523
3.3V 351 406
1.1V 23 0 (giving 1.400 and drop to 0 real flat)
8.7V 625 680
8.7V 508 577
1.68V 25 91
1.8V 128 257
8.2V 461 493
5V 369 402
1.8V 218 298

So, should I apply a low voltage on the coil 1.1V to find any cap getting hot ?

[mon2]

1.1V 23 0 (giving 1.400 and drop to 0 real flat)

Indeed, this rail appears to be shorted. Let us confirm another way. Remove all power. Meter in resistance mode this time. Measure the resistance to ground on either side of this same inductor. What is the resistance in ohms?

Hoping that you have only a shorted capacitor onboard. The next logical step will be to consider the voltage injection as you have noted. Keep the voltage low - suggest 0v8 to 1v0 (max). Being a hard short, the shorted part will crack / heat up quickly. If you have a thermal camera, the part will offer a throbbing thermal signature. Alternatively, you can pour IPA on parts suspected to be the defective and shorted. The IPA will evaporate quickly with the heat from the voltage injection.

[titomno2]

Around the 1.1V coil I have 6.58Ohms on left and almost the same on the right side of the coil.
It seems a bit high for a direct short, I will try to inject 0.8V this evening after work (I have a thermal camera so if anything is obvious I should be able to see it).
I hope the PCH or CPU are not fried, my friend told me he struggleling more and more to power on the tablet and was thinking the power button was bad!
I keep you posted.

[titomno2]

So injected 0.7V limited to 2 Amps.
But nothing only 0.1A consumption and nothing heating up, (to be honest not very surprised as the resistive value was quite high 6.7Ohms).
I think I have to dig on the U6001 (but I'm afraid it will drive me to the CPU at the end)


My son is sick today so no more digging this evening...

[titomno2]

Without power I measured some resistors around U6001 to find something close to the value 6.8OHms.
The R6023 is not populated
The R6022 is measured at 6.8Ohms
The R6021 is measured at 5.6kOhms
The R6012 is measured at 500Ohms

According to the schematic R6022 should be 10kOHms and R6021 should be 11.8kOhms.
Even if my multimeter is not a top one usually I have readings close to specifications.

[titomno2]

Hello,
Some updates.
I have received a new battery and tried it, the charging is working properly.
So I checked again for the button but the accessibility of the pins is too small for my probes.
And making measurement lead me to touching the read terminal of R5819(3.3V) and the SIL_SLP_S3_DRV#(1.8V) following that Have the feeling the processor getting hot (and it was properly).

So if someone can give me some advice on how to properly test the power button and or simulate the power button behavior I can double check this?



Last thing I screw up the screen ribbon (the scren is dead and the backlight was working).
I tried to plug a usb-c screen but I think due to the numerous boot attempt I may have something ot validate on the screen to go into windows and have the usb-ce DP working.

Here I am, I was not careful enough when opening the screen and kill the ribbon I see sparks when I plug it on the motherboard.

[titomno2]

Finally the power button was the culprit.
With all information shared with mon2 I have learn enough to solve another issue on a second board.
If someone have the same issue he can test by shorting with a wire or metallic tweezer the pin 1 with ground.

Both boards are working.
Have a nice day guys.