Lenovo G50-70 No display .

[lapfix]

Hello my friends.

Lenovo G50-70 NM-A271
No display , only 0.350 amp taken .

History = It comes with short , i find that Pu 1204 PWR_VGA_Core is very hot , desoldered = no short...resold another one , Lap work .
PWR_LED# light ok ..BATT_LOW_LED# blinking because no bat...Don't react with button = can't power off...tha lap works once adapter is inserted because i desoldered the batt coin...fan don't spin too

Impedance are OK
Voltages are OK :
PL 302 = Batt coil = 1.8v

VGA :
PL 704/705 = +VGA_CORE = 1.008v

PL 701 = +1.05VS = 1.056v

VRM section :
PL 9 = CPU_CORE = 1.8v

StepDown section :
PL 303 = +3VALW = 3.42v
PL 304 = +5VALW = 5.11v

Q23 = 5Vs present
Q24 = 3Vs present

Bios pin 8 = 3v
PLT_RST#= 0v !...must be 3v

UE1
EC_RSMRST# = 3v
DPWROK_EC = 3v
PCH_PWR_EN = 3v
+3VALW_PCH = Q29 = 3v
EC_RSMRST = 3v
PBTN_OUT = 3.3
PM_SLP_S3 = 3v
PM_SLP_S4 = 3v
PM_SLP_SUS = 3v
EC_ADAPTER_R= PM_SLP_S5 =0v
SYSON = 3v
SUS_VCCP = 3v
SUSP = 3v
EC_VR_ON= 3v
PCH_PWROK = 3v
SYS_PWROK = 3v
SUSACK# = 0.167v


ADAPTER_ID = 0.296v -----1.386v!

So no pltrst , no CPU_DRAMRST...
Change Ram , dump another bios still the same...what i miss !!

[lapfix]

Re: Lenovo G50-70 No display .

Hello...again

Another same motherboard but different behaviour !
Power on , only backlight fluctuation , all voltages are present , pltrst , DRAMRST also.


+LEDVDD / +LCDVDD_CON are ok but no DISPOFF# and no INVT_PWM...no corrision and no short to GND

Notice : the lab power on without trigger power button and no fan at all

So i suspect bios , try another main bios + io =

the lap power on now with button , backlight is ok , DISPOFF# and INVT_PWM got there 3 v but nothing else ...no Fan and no picture ! ad power off after a moment

A graphic issue !! or i must check other thing

[rediii]

Re: Lenovo G50-70 No display .

Hello...again

Another same motherboard but different behaviour !
Power on , only backlight fluctuation , all voltages are present , pltrst , DRAMRST also.


+LEDVDD / +LCDVDD_CON are ok but no DISPOFF# and no INVT_PWM...no corrision and no short to GND

Notice : the lab power on without trigger power button and no fan at all

So i suspect bios , try another main bios + io =

the lap power on now with button , backlight is ok , DISPOFF# and INVT_PWM got there 3 v but nothing else ...no Fan and no picture ! ad power off after a moment

A graphic issue !! or i must check other thing

try converting to uma: https://www.youtube.com/watch?v=Qr0D2CUGuBM

[lapfix]

Re: Lenovo G50-70 No display .

try converting to uma: https://www.youtube.com/watch?v=Qr0D2CUGuBM

Thank Rdii , yes i try this too but same behaviour

Q16 and RC181 aren't populated , i just remove pl704

[mcplslg123]

Re: Lenovo G50-70 No display .

Bios chip located too close to SOC?? It may be due to heat applied while soldering the chip that you got INVT_PWM back. 3VS/5VS is not dropping?? This mobo has tendency of voltage drop on 5VS. So do check these points.

[lapfix]

Re: Lenovo G50-70 No display .

Bios chip located too close to SOC?? It may be due to heat applied while soldering the chip that you got INVT_PWM back. 3VS/5VS is not dropping?? This mobo has tendency of voltage drop on 5VS. So do check these points.

Thank you mcplslg

3/5 VS are stable until the lap power off by himself

+5VS_FAN / EC_FAN_SPEED = 3v present
EC_FAN_PWM must be check by ocsillo...don't have

I try another bios version same behaviour : only backlight , no lenovo logo consumption reach0.93 (3 digit ) and stuck there , no fluctiation , no power off

[lapfix]

Re: Lenovo G50-70 No display .

Try 2 method of uma enable same behaviour : only backlight , no fan spining , no picture

[mcplslg123]

Re: Lenovo G50-70 No display .

Might be EC IT8586E is defective(Just a wild guess for now but deep probing it may give confirmation). At 0.93A consumption fan should rotate atleast a bit. Are you sure fan is not bad? Try disconnecting the fan and check it manually by injecting 3V on red wire and Black wire of fan to GND of your dc. Does the fan rotate?? The fan should not be connected to mb while doing this test.

[lapfix]

Re: Lenovo G50-70 No display .

Weired !
The fan doesn't rotate ...and if i power on the lap without fan same behaviour = backlight no picture !
is the detection of fan necessary to get picture!!!
ite is defective !!

[mcplslg123]

Re: Lenovo G50-70 No display .

Laptop should give display irrespective of fan being connected or not.
Since fan is tested bad, now i'm more inclined towards a bad EC.
Try flashing the EC first. Usually EC wont read/write successfully if it has problem.