Lenovo G50-45 NM-A281

[RethoricalCheese]

Fault: No power

Found that G and S on PQ6 and PQ7 were shorted so I replaced them.
After replacing, there is 1V on B+ and it rises up to about 5V in a minute or so. There it stops.

When I removed PJ2, there was a nice 20V present so up to PJ2 it should be working okay now.

Soldered PJ2 back on and tried removing PJ401, PJ405, PJ501 and PJ604 instead but still the same issue.

So I tried replacing PU4, still same Even tried removing PQ11, PQ12 and PQ8. Still same.

No dedicated video on this board.

Running out of ideas what do try next.

[caspian]

Re: Lenovo G50-45 NM-A281

remove PJ2 and measure resistance on each side of it.

[RethoricalCheese]

Re: Lenovo G50-45 NM-A281

Power adaptor side is about 13M and climbs to 20M+.
PR53 side is about 3M.

Forgot to mention that I replaced AO4407A with MDS3604 and Si4483 with AO4423.

[caspian]

Re: Lenovo G50-45 NM-A281

now measure resistance across PR53.

[RethoricalCheese]

Re: Lenovo G50-45 NM-A281

Close to a short as it should be.

The previous readings were measured while PJ401, PJ405, PJ501 and PJ604 were still removed, forgot to say that.

[tomodachi]

Re: Lenovo G50-45 NM-A281

What resistance on PL401 and PL402 ?
and also check LDO output of PU401, see if there is a short to ground

[RethoricalCheese]

Re: Lenovo G50-45 NM-A281

As I said, I have desoldered PJ401 and PJ405, thus the problem should not be related to them.

That said, resistance on PL401 is around 5.75k and on PL402 is over 20k. No shorts found there.

[tomodachi]

Re: Lenovo G50-45 NM-A281

you can inject low current 20V thru PJ2 and see what is heating up on +B line

[RethoricalCheese]

Re: Lenovo G50-45 NM-A281

Did that. Only 20mA consumption. 3.3V and 5V are present.

IT8586E needs reprogramming?

First it consumes about 5mA, then drops to around 2mA and jumps up to 20mA and stays there. Power button has no effect.

[ravi_1617]

Re: Lenovo G50-45 NM-A281

Hi
Same Board .
a liquid spill case ,Its dead no power at PJ2 at all.at PQ7
source 19.65 volts
Gate 19.54 volts
PC433 was short,
PR61 Blows of .

Where to begin .
Thanks

[on/off]

Re: Lenovo G50-45 NM-A281

Hi
Same Board .
a liquid spill case ,Its dead no power at PJ2 at all.at PQ7
source 19.65 volts
Gate 19.54 volts
PC433 was short,
PR61 Blows of .

Where to begin .
Thanks

1. Clean the spilled, and remember that area maybe help to find the culprit.
2. Isolate the shorted, where block/voltage rails was short. open PJP power jumper to help more easy. (Compal or LCFC family had this feature)
3. If have bench power supply try inject with low volt. (be carefull).
4. Seem PU4 was broken, indicate by due blown PR61.