Dell XPS 15 7590 LA-H331P EDP51 no power

[marcus6100]

Hi,
my 7590 spontaniously rebooted and showed "workshop mode press ALT-F" in BIOS post, then worked normally for two days, after shutdown a few hours later is dead and doesn't power on.
After a few hours of measuring I didn't find anything obvious, although the 2.5 Ohm measured might be too low, but I never fixed a notebook before (only other things like TV power supplys)
Found the boardview cad and schematics in this forum.

Voltages +1VALW, +3VALWP, +5VALWP, B+, +SDC_IN, +3V_PCH are ok
+3VS and +5VS is 0 because signal RUN_ON_EC is 0 and UZ1 doesn't switch on, which is controlled by PCH
+VCCST is missing, because signal SUS_ON_EC_ST is 0 and UZ15 doesn't switch on.
32kHz crystal is working.
The battery indicator doesn't show anything when it's button is pressed and battery is half full, it's LED outputs are controlled by PCH.

SUS_ON_EC_ST seems to be or result of (SUS_ON_EC_R, SIO_SLP_S4#) but both are 0 and
SUS_ON_EC_P is connected to SUS_ON_EC_ST
SUS_ON_EC_R is connected to SUS_ON_EC and SIO_SLP_S4#
I got stuck here and couldn't figure out how that works.

So far I didn't do anything stupid. Perhaps someone knows what I should look for?

Thanks
Marcus

[mon2]

Help me out in fixing a XBR 75" TV for a friend. Power supply appears to be the fault and now have the standby voltage working but appears that the opto-couplers are defective. The Sony white power on LED and relay are not engaging. As far as we know, it is the main power supply that must be working before the relay will be on. We have 3v45 (standby); 12v is working; using a wire to enable the T-con -> T-con rail enables ok @ 12v.

On your case, review the PS_ID line which is used by Dell to interrogate the power adapter's power rating. This is over a 1-wire communication line. Often this is the root cause. If this line is absent or not making it to the EC, the CPU speed will be throttled and the battery charging will be disabled.

Do review the sticky above by piernov on charger circuits. While you have the alw on rails, there may be a leaky mosfet. Do also check the resistance from this main power rail to the CPU power rail(s). If the resistance is low, then the high side mosfet on the CPU rail may be leaky.

[mcplslg123]

No point looking for VCCST and other such cpu rails unless 3VS/5VS is working. ON Pg5, power sequence is given. RUN_ON_EC will come after lot many signals/rails.
Since its not turning on ,you shoud check RTCRST#/SRTCRST# also. RSMRST# should be checked. What about 1.8V ALW rail?
However, i dont think its PS_ID related issue as even if there is problem,mb will turn on but will not charge.