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

[robgerr]

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

i disconnect every time for measure resistence

[caspian]

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

so these voltages are fine. now check resistance on PL710 and PQ302 relative to GND.
I think it is time to replace a new PQ304 now.

[robgerr]

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

I'm trying to understand the mainboard screen printing but pl710 is not present, but I have pl709 anywhay resistence pl709 6 Mohm
PQ302 pin 1,2,3 392kohm
pin 4 158kohm
pin 5,6,7,8 go up 20 Mohm

[caspian]

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

that is right. It is time to replace a new PQ304 now before you change any other component. after the replacement, measure voltages on pins of PQ302. Find a good replacement for PQ304.

[robgerr]

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

Replaced PQ304 from other mainboard (DTA144EUA).
Same problem.
Measure on PQ304:
pin 1 18,40v
pin 2 19,80V
pin 3 20,01
measure PQ302:
pin 1,2,3 19,77v
pin 4 19,95V
pin 5,6,7,8 1,80v

[caspian]

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

so we have made no great progress yet. now remove PQ302 and measure voltages on PQ304.

[robgerr]

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

PQ302 removed.
Voltage PQ304:
pin 1 19,7V
pin 2 19,9V
pin 3 20,1 v

[caspian]

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

now that PQ302 is removed, try to replace PQ302 by a new one which you know is healthy.

[robgerr]

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

ok, now I see to find it. I was doubtful if the problem could depend on an charger IC

[caspian]

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

yes, it is possible. ACOK should be high but it is zero. to check it, measure voltages on pins 5,6,12,16,19,20 of PU301.

[robgerr]

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

Replaced for safe pq301 and reflow zone with flux and laptop start normally. Testing...

[piernov]

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

bq24737 ACOK is active low so this is fine. The issue really seems to be at the voltage divider PR303/PR307.

[caspian]

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

does it charge the battery now?