Lenovo Ideapad 100 NM-A681 no display

[ruletero]

Hi everyone

Please help me with this laptop:

brand: lenovo Ideapad 100
Mobo: NM-A681 Rev 1.0
Fail: It turn on without video

It consumes 128 mA with or without Ram, SOC stays cold, have programmed several bios, not success, doesn't release PM_DRAM_PWRGD (CPU_DRAMRST# in schematic.

This is the power secuence measurements:

PCH_PWR_EN 3.3
+3VALW_PCH 3.3
EC_RSMRST# 3.3
PBTN_OUT# 3.3
PM_SLP_S3# 3.3
PM_SLP_S4# 3.3
PM_SLP_S5# 3.17
SYSON 3.3
SUS_VCCP 3.3
SUSP# 3.3
VR_ON 2.83
VR_READY 3.3
PCH_PWROK 3.3
SYS_PWROK 3.36
PM_DRAM_PWRGD 0.123
H_CPUPWRGD (VR_CPU_PWROK) 1.05
PLT_RST# 0


And this general measurements:

PL501 1.35 +1.35V
PL303 3.38 +3VALW
PL304 5.07 +5VALW
PL9 1.7 CPU_CORE
PL701 1.05 +1.05VS
PL302 0.6 BAT+
PJ712 1.5 +1.5VS

DDR 3L ram section voltage check list at ram slot (in red my measurements)

DDR3L operating voltage VDD (at coil )= 1.35V PINs 75,76 ram slot 1.35V
VRef_DQ = 0.67 V at PIN 1 0.69
VTT/Termination voltage= 0.67V PINs 203,204 0.66 pin 204 0.67
VRef_CA. = 0.67V PIN 126 0.67 pin 126 0.67
VDD SPD = 3.3V PIN 199 3,32 pin 199 (without ram) 3.3
SDA data = 3.3V PIN 200 3.30 pin 200 3.38
SCL clock = 3.3V PIN 202 3.30 pin 202 3.38
DRAM_RST# = 1.35V PIN 30 0v pin 30 0.112


KBC

SYS_PWROK 30 3.36
PM_SLP_S3# 18 3.3
PM_SLP_S4# 21 3.3
PM_SLP_S5# 106 3.17
VR_CPU_PWROK 70 1.05
EC_RTCRST#_ON 73 0
MAINPWON 79 2.64
PCH_PWR_EN 97 3.3
PCH_PWROK 99 3.3


What other thing could I check?

Please and thank you for your support

[Techtiger]

Re: Lenovo Ideapad 100 NM-A681 no display

Thé voltage in DRAM_RST# is +1.35V or 0.112 ! If 0.112V trace it back

[ruletero]

Re: Lenovo Ideapad 100 NM-A681 no display

DRAM_RST# (CPU_DRAMRST# in schematic) is only 0.112v and comes directly from PCH.

[mcplslg123]

Re: Lenovo Ideapad 100 NM-A681 no display

If you have a scope observe the pulse in VDD_SPD/SDA/SCL pins on ram slot.

[ruletero]

Re: Lenovo Ideapad 100 NM-A681 no display

mmm no, I don't have scope . I'm going to try to get one

thank you