Lenovo Z50-70 ACLUA/ACLUB NM-A273

[vpower]

Hi, I have this laptop, it is completely dead, no charging light when connected to a working charger.
Can anyone help me with some hints for troubleshooting this laptop?
Thanks in advance

[mon2]

See attached. Measure and post the voltage to ground of the DCin mosfets @ PQ301 / PQ302. Source / gate / drain pins.

(review the above sticky by piernov on charging circuits)

[vpower]

See attached. Measure and post the voltage to ground of the DCin mosfets @ PQ301 / PQ302. Source / gate / drain pins.

(review the above sticky by piernov on charging circuits)

thank you.

PQ301
pin 5-6-7-8=19v
pin 1-2-3=19v
pin4=19v

PQ302
pin 1-2-3=19v
pin4=19v
pin5-6-7-8=PR301=voltage is fluctuating fron 2v to 19v, the board makes a clicking sound each time the voltage value changes

[mon2]

Replace PQ301 and test again.

[vpower]

PQ301? isn't PQ302 failing with voltage?
ok I'll replace PQ301 and report

[vpower]

Replace PQ301 and test again.

hi, PQ301 replaced, still not working, same values and still same clicking sound (unable to understand which component is making that sound)

[mon2]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PQ302 (drain pins 5-6-7-8). This is the main power rail. What is the resistance measurement?

The clicking sound will be from a local switching power supply that is pulsing on / off and the switching frequency is being heard by yourself. The power supply is pulsing because the mosfet driver (charger IC) is sensing a higher than normal current draw so powering down this main voltage rail. The cycle repeats once it is OFF - aka chirp mode of power supplies.

[vpower]

Remove all power. Meter in resistance mode. Measure the resistance to ground of PQ302 (drain pins 5-6-7-8). This is the main power rail. What is the resistance measurement?

The clicking sound will be from a local switching power supply that is pulsing on / off and the switching frequency is being heard by yourself. The power supply is pulsing because the mosfet driver (charger IC) is sensing a higher than normal current draw so powering down this main voltage rail. The cycle repeats once it is OFF - aka chirp mode of power supplies.

multimeter says open circuit on drain(no value). same on gate and source

[mon2]

What is the voltage to ground of the gate pin # 4 of PQ302? Is this a stable 19v to ground?

Remove all power -> meter in resistance mode. Measure the resistance across this mosfet's pins:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

With the gate pin @ 19v on this N-channel mosfet, this mosfet should be OFF. N-channel requires a boosted voltage and it should be higher than the voltage being passed between source / drain pins.

Checking to see if this mosfet is shorted or not through the resistance checks. A good mosfet should have high resistance readings for each of the above permutation checks.

[vpower]

What is the voltage to ground of the gate pin # 4 of PQ302? Is this a stable 19v to ground?

Remove all power -> meter in resistance mode. Measure the resistance across this mosfet's pins:

source (1-2-3) & drain (5-6-7-8)
source (1-2-3) & gate (4)
gate (4) & drain (5-6-7-8)

With the gate pin @ 19v on this N-channel mosfet, this mosfet should be OFF. N-channel requires a boosted voltage and it should be higher than the voltage being passed between source / drain pins.

Checking to see if this mosfet is shorted or not through the resistance checks. A good mosfet should have high resistance readings for each of the above permutation checks.

gate pin #4 of PQ302 is 19v but not stable. sometimes goes down to 16v
source (1-2-3) & drain (5-6-7-8) open circuit
source (1-2-3) & gate (4) open circuit
gate (4) & drain (5-6-7-8) open circuit

[mon2]

You should have a resistance measurement.

Is your meter auto scaling or manual? If manual, switch to a higher resistance scale on the meter.

No power during these tests.

[vpower]

You should have a resistance measurement.

Is your meter auto scaling or manual? If manual, switch to a higher resistance scale on the meter.

No power during these tests.

sorry. scale to 20 megaohm
PQ302 measurements to ground
pin 1-2-3 15 megaohm and raising over multimeter range
pin 4 same as pin 1-2-3
pin 5-6-7-8 3.4 megaohm

[mon2]

Ok but not checking resistance to ground. Review post # 9 again.

[vpower]

Ok but not checking resistance to ground. Review post # 9 again.

source (1-2-3) & drain (5-6-7-8) 5 megaohm raising over multimeter range
source (1-2-3) & gate (4) 0,40 megaohm
gate (4) & drain (5-6-7-8 5.5 megaohm

[mon2]

The mosfet is being switched ON / OFF using the gate pin so you are observing the fluctuations to the best ability of the meter. An oscilloscope is needed to properly view the switching action. This power cycling event may be due to the charger IC believing there is too high of a current draw but you are not measuring a short on the main power rail.

Remove all power. Meter in lowest resistance scale (required). Measure the resistance between pins 1 & 2 on the charger IC @ PU301. These are the ACP / ACN pins where the charger IC monitors the voltage that enters this main power rail (ACP) and measures the voltage that leaves the current sense resistor @ PR301 @ ACN pin. The small voltage drop is used to gauge how much current is being consumed by the main power rail. If it is too high, the mosfets will be shut off to prevent damage.

Post the measurement but be sure to measure the resistance of this path directly on the charger IC pins. Again - with no power to the board.

[vpower]

The mosfet is being switched ON / OFF using the gate pin so you are observing the fluctuations to the best ability of the meter. An oscilloscope is needed to properly view the switching action. This power cycling event may be due to the charger IC believing there is too high of a current draw but you are not measuring a short on the main power rail.

Remove all power. Meter in lowest resistance scale (required). Measure the resistance between pins 1 & 2 on the charger IC @ PU301. These are the ACP / ACN pins where the charger IC monitors the voltage that enters this main power rail (ACP) and measures the voltage that leaves the current sense resistor @ PR301 @ ACN pin. The small voltage drop is used to gauge how much current is being consumed by the main power rail. If it is too high, the mosfets will be shut off to prevent damage.

Post the measurement but be sure to measure the resistance of this path directly on the charger IC pins. Again - with no power to the board.

lowest scale is 200ohm
measured resistance between pin 1 and 2 of PU301 is 1,8 ohm .

[mon2]

While using the same resistance scale - short your meter probes. What is the measurement?

[mcplslg123]

Remove the CLR and measure voltage on PQ301/302 gates again.

[vpower]

While using the same resistance scale - short your meter probes. What is the measurement?

1,4 ohm

[mon2]

Post # 18. Remove the current sense resistor (CLR) that is after the dcin mosfets.