Lenovo IdeaPad 3 NM-C961.no display

[lapfix]

Hello everyone.
lap and motherboard : IdeaPad 3-15IGL05 Laptop - Type 81WQ
NM-C961.
Behaviour : connect charger it power on automatically ,reach 0.170 amp than down to 0.74 amp...no display.
with battery connected it reach 980 amp than 870 ...no display
No short ; no corrision no intervention before.
Try 2 differents bios versions same behaviour.

Some measuremets :
PL 1600 = 5valw present
pl 1100 = 3 vlalw present
pl 100 = 0.221 v without battery and when battery connected 7.8 volt
pl 6602 = 1.2 v
pl 6603 = 1.056v
pl 6604 =0.807 v
pl 6601 = 0.732 v
pl 6606 = 1.2valw
pl 6605 = 1.8 alw
3/5 vs present
1.8 vs present
1.05vs present

Vcc rtc =3.2v
rtcrst = 3.2v
+2.5v ddr present
Drmrast 1.2v present
+3valw_soc present
pltrst =3.3v present
Alw_pgood = 3.3v present

5 valw pgood = 3.3v present
3 valw pgood = weired behaviour , somtimes i find 0.5v and sometimes 5 v and start to downgrade.
rsmrst 3.2v present.

Schematic and BRD :

Any other idea to check !!

[mcplslg123]

Measurements are all fine. Have you checked communication on LPC lines like LPCLAD/LPCFRAME/LPC CLK etc?

Can be checked only on DSO.

[lapfix]

Thank you mcplslg
unfortunately not .

I tested everything around the BQ nothing that gives me a doubt..

the fact that the pc starts with a consumption going up to 0.170 amp then it drops to 0.65 amp and that all the voltages are always the same ..so it's a problem of power !!
My only doubt is for the integrated memory..especially that it does not have a socket for an external so i can't disable it via bios to be sure...nothing to add...
End of story !

[mon2]

Confirm the voltage to ground of:

RT5077A_VCC ; stable?

ALW_PGOOD ; stable? This is an output signal from PU6601 RT5077AGQW_WQFN52_6X6

+3VL ; pin 13 LDO output on PU1100

+5VLP ; pin 12 LDO output on PU1600

ACOK ; pin 5 on PU100 (charger IC)

[mcplslg123]

I dont agree with your observatione on post#3. Its rather expected that consumption should drop to such low level after going to its peak consumption. Moreover, this indicates that onboard ram is perhaps working fine
and ram is correctly read/recognised..

Yeh these small SOC's tend to fail 'coz of poor aluminium heatsink and fanless designs in most cases.

I beleive your programmer supports 1.8V chip as the chip used here is 1.8V.

[lapfix]

@mon2

RT5077A_VCC = DDR_SEL
pin 23 = 0.030v than drop slowly
resistance = 20 mohm and drop slowly
diode = 0.633
the PR6633 and PR6637 are not populated but i find my 5v stable at PR6633 pin 1
notice that this is a onboard ram , no socket for external ram
ALW_PGOOD = RSMRST#
pin 36 = 3.3 stable
+3VL = pin 13 LDO output on PU1100 3v stable
+5VLP = pin 12 LDO output on PU1600 5v stable
ACOK = pin 5 on PU100 (charger IC) 3.3v stable

mcplslg123

Yes you are right : " these small SOC's tend to fail 'coz of poor aluminium heatsink and fanless designs in most cases.
"
i'm using a virgin bios ,the main is CN21WW and i only find DVCN34WW and also using peste bios dvcn22ww but no chance
" I beleive your programmer supports 1.8V chip" yes of course