Lenovo G50-30 no display .(NM-A311)

[lapfix]

Hello my friends.
Lenovo G50-30 no post at power up , only 0.110 amp taken .

Impedance are OK .

PR 301 = 0.499v
Pl 301 = Batt coil = 0.544v

VRM section
Pl 901 = 0.013v
Pl 902 = 0.011v

StepDown section
PL 401 = 0.364v
Pl 402 = 0.378v

Ram
Pl 501 = 0.429v

Pl 701 = 0.336v
Pl 602 = 0.164v
Pl 601 = 0.352v

Voltages are OK .

Pl 301 = 1.879v
Pl 901 = 0.809v
Pl 902 = 0.762v
Pl 401 = 3.39v
Pl 402 = 5.13v
Pl 501 = 1.366v
Pl 701 = 1.020v
Pl 602 = 1.049v
Pl 601 = 1.796v

Q4601 = 5Vs present
Q4602 = 3Vs present
Q 26 =+3Valw soc present
Q 28 = 1.35vs present
Q 30 = 1.8vs present

Bios pin 8 = 1.8v
PLTRST= 3v
Sys on/ SUSP / VRON / SYSPWOL = 3v

DDR section
Vtt =0.670v
Vdd = 1.35v
SDA/Scl = 3.3v
Drmarst = 0v must be 1.35v !

Try another bios still the same ,so i try to measure powergood signal of each and every pwm as suggested here :
https://www.badcaps.net/forum/showthread.php?t=88408

Pu 501 = pin 20 = 3.35v
Pu 602 = pin 7 = 3.36v
Pu 701 = pin 7 = 3.36v
and i find my pb here :
Pu 401 = pin 2 = not stable
Pu 402 = pin 2 = not stable (7v ....10v.. 1.2v..0.300v..0.500v..)

As mcplslg say = PIN2 POWERGOOD should be 3V ...but i didn't find this voltage .
Pr 406/407/408 are not populated

What shoul i measure /change !!

[mcplslg123]

Re: Lenovo G50-30 no display .(NM-A311)

PU402 PG signal is drawn from +3V PG, so problem is likely in PU401. Unless PU401 pin2 PG is stable you wont get proper voltage at PU402 PG pin. Now you can try replacing PU401 first or cut the pu402 pin2 track to isolate pin2 of PU401 and see if you get PG signal on PU401 IC.Dramrst# is generated directly by SOC and no other component is involved. So could be SOC Fault as well.

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

Thank you my friend for your help.

I change Pu 402 and got screen at external ,1.35v at Drmarst and 0.18 amp taken ...(.just assemble to confirm at internal) , measure again pin 2 i find 0.700v...not 3V !

[Sametbey]

Re: Lenovo G50-30 no display .(NM-A311)

pu402 from 7 pin +5vlp fixed output. 1 pin 3.3 V when you get the signal, 10 pin +5VALW comes out. if there is no problem, the 3V PWGD signal will output from 2 pins. Check for problems at Output +5VALW.

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

pu402 from 7 pin +5vlp fixed output. 1 pin 3.3 V when you get the signal, 10 pin +5VALW comes out. if there is no problem, the 3V PWGD signal will output from 2 pins. Check for problems at Output +5VALW.

Thank you sametbey for your help , the issue is already fixed with changing Pu402...
As i mention before , the 5valw is present ,i didn't measure 5VL since i find my 5Valw , so for me this circuit is OK...

the only thisg i measure is PG ( not stable ) and must find 3v ..but even when i change PU402 still not find 3v at pin 2 !!..but the lap work !..that's my confudion!

[mcplslg123]

Re: Lenovo G50-30 no display .(NM-A311)

PU401 PG voltage now after repair??

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

PU401 pg = 0.542v..just takeoff the prob and try again = 0.620v

[Sametbey]

Re: Lenovo G50-30 no display .(NM-A311)

If there is 3.3VALW and 5VALW and the problem is the PW_GD signal, you can check it by canceling the PR407 and PR408 resistors to try. maybe IO can be problematic.

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

PR 406/407/408 doesn't exist at the motherboard

[Sametbey]

Re: Lenovo G50-30 no display .(NM-A311)

Are you stuck in step 3? You should now check the 87 pin of the IO ITE8586 chip. need 3v. if not, you can proceed with the other steps.

[Sametbey]

Re: Lenovo G50-30 no display .(NM-A311)

There is no problem with the PU402. If there is 3V at ITE8586 87 pin, PW_GD is OK. you have to look at the other steps. Like Q26, + 3VALW_SOC. It may be a bios and IO problem.

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

Thank you Sametbey...as i mention at first all the voltages are present (Q26,Pltrst ...etc)

As you said maybe the issue at first was bios/io/ or pu 402...now all is fixed by changing pu402 , and there's a picture at exrenal screen ,i will assemble again the lab and give the result.

[mcplslg123]

Re: Lenovo G50-30 no display .(NM-A311)

@lapfix, Sorry for misleading you on PG output voltage level on PU401/402. I beleived it should be stable 3V but that doesnt seems to be the case here. So confusing it can be..PG pull up is +3VALW and still 0.5-0.6 is the output on PG. I didnt expected that and hence the error in guidance. My sincere apologies.

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

Helo friends , back again after assemble the lap all is OK , but i face this message at boot : Unauthorized Wireless network card is plugged in. Power off and remove it.
also with his old dump !

What to do !

[mcplslg123]

Re: Lenovo G50-30 no display .(NM-A311)

This wifi message is 'coz of incompatible card. You need to replace the card. May be someone changed the card prior to you.

[francismusa]

Re: Lenovo G50-30 no display .(NM-A311)

there is no problem with the pu402. If there is 3v at ite8586 87 pin, pw_gd is ok. You have to look at the other steps. Like q26, + 3valw_soc. It may be a bios and io problem.

mine all these voltages are present up to r26 but still no display.what should i check next?

[lapfix]

Re: Lenovo G50-30 no display .(NM-A311)

mine all these voltages are present up to r26 but still no display.what should i check next?

Did you try to clean your bios or maybe he s corrupted !
Drmarst voltage !
PLTRST voltage !