No boardview and no markings on the board? Will not be an easy one... Can you post high resolution picture of both sides of the board? As much details as possible around the BIOS chip (trying to see where does SPI_PWR come from).
is it U20 rom ? if so tell me wich is the voltage found on PIN 121 of SIO KBC if not mistaquen its a IT8987E , if you have voltage on that pin , therefore you should have voltage on U20 as well on pin 7 ,8 and 3.
alltough PU11 releases the +3vpcu , so chek carefully first what it the impendace of the coils of 3.3 and 5 volts to ground , a nice way to find it out without boardview its simples in this case
to see wich coil is the 3.3 volts put your multimeter on diode/continuity mode)
PU11 pin 18 its the 5 volts coil so , with one prob touch pin 18 of pu11 and then chek with the outher prob on wich coil it will make continuity the one that does its the 5 volts coils , ~
pu11 pin 8 its the 3.3 coils , do the same thing above to find wich is the 3,3 coil , once you know , put your multimeter on 200ohm scale , and chek both coils to ground and let us know wich the ohm value you get and post it here for we can follow further
reading schematic near ROM it says its a W25Q80BWSSIG so its a regular rom feeded by 3.3volts .
altough if you chek on schematic R475 you will see that there are 2 lines for SPI_PWR one 1.8 on S5 state and the regular 3.3 .. so i guess this 1.8 will not be for this revision since bios is high voltage and now lowvoltage.
Seems like it is fed by 1.8V since it is the "W" variant, not the "V" one. But @dspok will confirm what he has actually got on the board.
SPI_PWR goes to U20 which is the EC ROM. I assume it is the one just right to the M.2 port.
There should be a 0ohm resistor around it which connects SPI_PWR to the +1.8V_S5 line.
+1.8V_S5 comes from PU9, which is also right to the M.2 port, just above EC ROM.
The top coil is +1.8V_S5. Which resistance to ground do you get there?
VCC pin 11 should be 5V, not 3.3V. If it is, the issue is either with PU9 itself or the output is indeed shorted.
Maybe start by removing PU9 in case it's shorting the feedback of +1.8V_S5.
Otherwise I've got no idea…
did you lft the bios and cheked if leg 8 is still with 6 ohm , and if so , dod you try to inject around 1 volts on that trace to see the consumption ? alltough cheking all pu9 , the EN's are coming from EC and some from PCH . so you're in a hard time here , because if you replace EC you need programmer to flash it via keyboard line . or at leastr try reprogram the IT8987 if you have a way of doing it .
but also tell me another thing , if you press ONOFF button on the machines , i conclude she does't turn on , but my question is , once you press the onoff button , if you chek the spi_pwr do you notice any kind of oscilation on voltage or impedance ?
let us know
VCC pin 11 should be 5V, not 3.3V. If it is, the issue is either with PU9 itself or the output is indeed shorted.
Maybe start by removing PU9 in case it's shorting the feedback of +1.8V_S5.
Otherwise I've got no idea…
Schematic says 3.3v as well, will try removing PU9.
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