Lenovo CG410/CG510 NM-A681 REV 1.0

[String2016]

I have this lenovo 100-151bd the problem is turns on display comes then goes off.already check some voltages, I found out that PQ39 drain side is shorted to ground in the schematic source goes to ground but this case drain is shorted, already tried removing the mosfet but still drain side is shorted to ground, inject 1v psu taking 0.045amp nothing hot. anyone can help this please

[mon2]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Wait..what is the resistance to ground of the drain pin of PQ39 ? Since this mosfet is used to power the low voltage rail for CPU_CORE, the resistance is expected to be low.

Low voltage rails are low resistance rails. Of course it should not be the same as shorting direct to ground but it will be a low resistance.

For example, on my Fluke 87V, the reading is 0.3 ohms - even when the meter probes are shorted.

That is, suspecting that you do not have a short on the CPU_CORE rail nor @ PQ39.

Can you confirm the exact resistance to ground of the drain pin(s) of PQ39 ?

Next, when the display goes off -> can you shine a flashlight / cell phone in torch mode in front of the LCD and check if you see the usual graphics ?

The fault may have more to do with the backlight circuit rather than the CPU rails.

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

@mon resistance to the ground of pq39 drain side is 7.1ohms , already checked tried also external hdmi same turns on display goes for 5seconds then fan goes off

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

same as PL9 Both sides beeping to ground

[mon2]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Ok - so CPU is ok since the logic board does turn on.

Suggest to remove all power -> check the resistance to ground of each coil / inductor on the board.

Each coil is linked to a local power supply / regulator. Perhaps some shorting cap is causing an excessive current draw and forcing this shutdown.

Also, be sure that your adapter is the known good unit and recommended for this laptop.

same as PL9 Both sides beeping to ground

This is possible with low resistance if the meter is in diode mode. Best to measure in resistance mode (no tones). For a CPU power rail, the resistance and the tone to ground is normal.

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Resistance of PL9 both sides have 10.4ohms all coils resistance good, I am using original charger

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

noticed also plugging in the charger it goes on directly tben display comes then goes off

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

pulled up 1 leg of coil PL9 short is gone on pq39 but the pads is still beeping to ground

[mon2]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Do not worry about PQ39 / PL9 area. Place them back like before. Your CPU does not appear to be shorted.

If you are having the logic board being powered on using the adapter, then review the DCin mosfets that power this logic board.

See attached. When you apply power -> what is the voltage to ground of B+ ?

When the logic board shuts OFF, what is the voltage to ground of B+ ?

Then attempt the wire jump to enable the same 2 x DCin mosfets (P-channel).

Connect a wire to pin # 2 of PR307 to ground to enable the gate pins of each.

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Ifound pq309 6pin but i cannot found PR307 , but i check the first dc in mosfet PQ301 And PQ302 both mosfet source have 20v but gate have 5v only even if turns on and shuts off still stead on 5v

[mon2]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Ok. Remove all power. meter in resistance mode.

Check if the DCin mosfets are defective by checking their resistance as follows:

source (1-2-3) & drain (5-6-7-8) ; one meter probe on source & other probe on drain - any pin inside the brackets is ok - they are shorted together for higher current support
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

Post each measurement and the meter scale used for the measurement.

If any of the measurements shows a low resistance value then the mosfet is defective and must be replaced.

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

pq301 black probe to source 123 and red to ground 5678 5.9megaohms black to source and red to gate pin4=198k and black probe to gate pin 4 and red to drain 5678 6.2megaohms same measurement with PQ302 EXCEpt for black probe to source and red to drrain PQ302 measure 6.4megaohms

[mcplslg123]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Ifound pq309 6pin but i cannot found PR307 , but i check the first dc in mosfet PQ301 And PQ302 both mosfet source have 20v but gate have 5v only even if turns on and shuts off still stead on 5v

PQ301/302 are fine. gate voltage is correct at 5V. They are P channel mosfets,so gate voltage will be lower then source.

[mcplslg123]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

Does the system shuts down with no ram stick installed??

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

@mcplslg123 removing ram stick its starts then shuts of and starts again and shuts off , with ram stick it starts display comes then goes off

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

I already check the sequence on dc in all are good according to schematic, I never tried reflashing the bios

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

problem solved

[mon2]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

By reflashing of the bios?

[String2016]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

no removing d1

[mcplslg123]

Re: Lenovo CG410/CG510 NM-A681 REV 1.0

But D1 is no pop component??