HP 250 G6 MB LA-E791P overheat and power off

[shybear]

hi,
I've here this laptop with CSL50/CSL52 LA-E791P Rev:2.0 mainboard.

Unlucky schematic of this MB isn't around anyway,
if I power the MB, jack led lights but when I press poweron button, on led lights but system shut down in like 5/10 seconds.

There is an overheating on area around PU301 (backside near USB ports) and on the other side near speaker jack:
as I press power on button PL301 overheat a lot.

Testing components near PU301 finally I found mosfet PQ302 shorted so I replaced it without any luck. For sure original component its shorted but at least the new one its still alive!

I think that IC PU301 its not damaged because I find 3,3V and 19,5V.


I didn't find any other short measuring components with tester but if
if I put some flux grease on IC PU301, and mosfet PQ301, PQ302 and power on mainboard it melt on all three components but I don't know if its due to the overheat of PL301!
Testing around the mainboard I didn't find any other overheating.

I also desoldered PL301 that its a coil marked 3R3 but doesn't looks bad or damaged.

There are some components that looks shorted but are good when i desoldered:
- protection diodes just back usb port.
- an elctrolitic metal capacitor just near PL301 (PC302).

I don't know what else try....any help would be really appreciated.

[mcplslg123]

Re: HP 250 G6 MB LA-E791P overheat and power off

First, replace the pwm(PU301) along with mosfets all at one time. Replace the mosfets even if they test good.

[shybear]

Re: HP 250 G6 MB LA-E791P overheat and power off

First, replace the pwm(PU301) along with mosfets all at one time. Replace the mosfets even if they test good.

Thanks and OK! I supposed it could be the PU301 IC so I'll try to desolder it, and next I'll exchange the mosfets anyway, lucky I bought 3 pieces last time.

I'll write here if all goes fine.

[shybear]

Re: HP 250 G6 MB LA-E791P overheat and power off

First, replace the pwm(PU301) along with mosfets all at one time. Replace the mosfets even if they test good.

Back again.
as you suggested I changed mosfets and PU301 but now all is dead.
It was really hard to change PU301 but it seem I did it good as attached picture.
Help please.

[mcplslg123]

Re: HP 250 G6 MB LA-E791P overheat and power off

Yes, the soldering seems proper. If mb was booting fine earlier and now its dead means the replacement ic is bad or it got killed 'coz of excessive heat apllied during soldering. You can check whether 3/5V LDO is present or not.

[shybear]

Re: HP 250 G6 MB LA-E791P overheat and power off

Yes, the soldering seems proper. If mb was booting fine earlier and now its dead means the replacement ic is bad or it got killed 'coz of excessive heat apllied during soldering. You can check whether 3/5V LDO is present or not.

Just before to solder the new IC I had a sort of doubt that maybe it was defective because as you can see in the other picture I made before to solder it there is a little crack in the upper right corner that I suppose it was a factory defect because component was in its original package.

Anyway I'll also check 3/5V.

[petehall347]

Re: HP 250 G6 MB LA-E791P overheat and power off

2.2 resistor looks like it been hot