Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

[robgerr]

Good afternoon forum. This laptop has the following defect: It does not turn on, no LEDs, it does not charge the battery. Dismantling the board on the bench, I checked and did not exit B + from PQ302.
On the source I find 19,80V
On the drain 0.90V
On the gate 19.20V.
I tried to remove the mosfet and jumper drain and source and the machine turns on perfectly,
Not having SI4483 I tried to replace it with AO4407 but nothing.
Another thing I noticed but I do not know if it can help, on the power connector, ADAPTER_ID is at 0v
I think the flaw starts from the bad pilot signal of pq302 in the gate

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

what voltages are on the three pins of pq302 after the replacement by AO4407?

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

what voltages are on the three pins of pq302 after the replacement by AO4407?

Same of old mosfet

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

try to replace with ao433 but nothing.
voltage pin 1,2,3 20,2v
voltage pin 4 (gate) 18,4v
voltage pin 5,6,7,8 0,91v

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

I think the gate voltage should be lower. thus, check voltages on PQ304 and PQ307B and PQ998A.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

pq304:
pin 1 19,9v
pin 2 20,1v
pin 3 18,6v

pq307:
pin 1 0v
pin 2 3,20v
pin 3 0v
pin 4 0v
pin 5 3v
pin 6 0v
PQ998
pin 1 0v
pin 2 0v
pin 3 3,34v
pin 4 0v
pin 5 0v
pin 6 3,30v

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

they seem fine. now, check voltages on PQ990.

edit: I think you exchanged voltages of pin1 and pin3 of pq304 by mistake.

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

In addition, check resistance between pin1 and pin4 of PQ302.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

PQ990:
pin 1 0v
pin 2 0v
pin 3 0v
pin 4 0v
pin 5 0v
pin 6 19,03 v
pPQ302:
res pin 1-4 195kohm

sorry for pq304 but i think this pin out:
http://pinout.net/transistors/B.gif
is correct?
anywhay pin 1 19,42v
pin 2 19,78v
pin 3 19,59v

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

At this point, there is no clue to find the faulty component. Now as a try, you can remove PQ304, then start the laptop. If it started normally, probably PQ304 is faulty. Otherwise, if there was no voltage at the drain of PQ302, resolder PQ304 at its place on the mainboard. I hope this method work, because finding the faulty component gets really difficult then.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

Thank you. then I removed pq304 is the laptop had turned on. I connected the battery to test the charging, the orange led started to flash. I think he was starting to charge the battery. After ten minutes I find all the LEDs off, I try to turn on and nothing again, I try to remove the battery and try again with adapter but nothing. What I understand is starting to be difficult to repair quwsta mainboard. Do you have any other ideas?

[piernov]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

Check voltage on PQ302 and PQ307 again. Maybe when you removed PQ304 something heated up and that temporarily fixed the issue.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

pq302 same value
pq307:
pin 1 0v
pin 2 2,92v
pin 3 0v
pin 4 0v
pin 5 3,03v
pin 6 0v

[piernov]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

It seems like you're exactly in the same situation as before, but with PQ304 removed right?

Check resistance across PC308.

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

the battery should not be connected. However, I think no severe damage is made to the mainboard. At least, you discovered that pq304 has to be replaced later.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

It seems like you're exactly in the same situation as before, but with PQ304 removed right?

yes.

checked pc308, no shorted

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

the value of resistance across pc308 is important. please mention it. In addition, check all the points near PQ302 and PQ304 for being shorted or having a voltage other than your previous measurements.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

sorry, 198kohm

if I invert the tips, 130kohm

[caspian]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

disconnect power every time you connect it to the mainboard in this situation. now continue Post17.

[robgerr]

Re: Lenovo G50-80 No power on (no led) (ACLU3/ACLU4 UMA NM-A362)

checked PQ998, same value
checked pq304 pads (ic removed):
pin 1 0v
pin 2 19,80v
pin 3 20,2v