ACER ASPIRE 5517 burnt MOSFET

[nearxos]

Hello.
I got a faulty Acer Aspire 5517. took it apart and found a burnt mostfet (PQ35).
through the schematics i found online i order some new mosfet a replace it.

i re assemble the laptop to test it. and when i pressed the power button the laptop work for a few second (fan and power led turned on)and then stop.

Took the laptop apart and checked the mosfet with a DMM and Drain and Source was shorted.

i replaced the mosfet once again cause i though i didnt solder it well. but the same thing happened.


above the mosfet i replace there is another mosfet(PQ36). Now the Source of PQ35 is Connected to the Drain of PQ36 acording to the schematics.

Checking with the DMM i see that its connected to ground but according the the schematics its not.

the schematic i have is this one. on page 42 you can see the relative circuit.

https://www.badcaps.net/forum/showth...er+aspire+5517

what else should i check around the mosfet? nothing else seems to be burnt.

Not a native english so sorry for anything that doesnt making any sense in my writting.

Thanks in advance

[bushie]

Re: ACER ASPIRE 5517 burnt MOSFET

change that integrated circuit PU12 : tps51117

[pcbmaniac]

Re: ACER ASPIRE 5517 burnt MOSFET

Greetings from Hellas.
Before give dc power, do some measurements for low resistance to all inductors with earth. If you find normal resistances, give power and BEFORE press the power button, measure to all inductors looking for 3,3V and 5V as well. Do that and then we talk again.

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

nearxos> check pq36 for short. if it is shorted, after the power button the vin is shorted through pq36 and high current blow pq35

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

Greetings from Hellas.
Before give dc power, do some measurements for low resistance to all inductors with earth. If you find normal resistances, give power and BEFORE press the power button, measure to all inductors looking for 3,3V and 5V as well. Do that and then we talk again.

Gia sou. kiprios eimai

What will be a normal resistance messurement for the inductors. will it be in the range of ohms or Kilo ohms?

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

forget about it u have 3.3v and 5v good. 3.3 and 5v must be good to power on so u have it good.

system detect short on switched powerrail and power off because didnt have PWRgood signal. in your case SUSGD or something like that.

Focus on pq36 or short on that power rail.

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

nearxos> check pq36 for short. if it is shorted, after the power button the vin is shorted through pq36 and high current blow pq35

I took out the pq36 and check it..it doesn't seems to be shorted. BTW what's the correct way to check if a MOSFET is shorted?

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

if u took it out check for short on that rail

but how do u know that pq35 is shorted when dont know how to check if it is shorted?


look on youtube how to check it, because when u dont know , u can bad check and think it is shorted

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

i laptop is work for only few seconds check all power coils for woltage and if u find no woltage on some check on it for short.

i think u have amd northbridge so u can have shorted its rail

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

i laptop is work for only few seconds check all power coils for woltage and if u find no woltage on some check on it for short.

i think u have amd northbridge so u can have shorted its rail

no voltage on any of the power inductors in check

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

that means no start and u wrote this
"i re assemble the laptop to test it. and when i pressed the power button the laptop work for a few second (fan and power led turned on)and then stop."

so u must have some voltages on some powerrails.

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

that means no start and u wrote this
"i re assemble the laptop to test it. and when i pressed the power button the laptop work for a few second (fan and power led turned on)and then stop."

so u must have some voltages on some powerrails.

after the first attempt to replace PQ35 it did start for a sec.
Now it wont start at all.

i start check from the power jack.

on the power jack i got 19.5V
the on PL1 19.5 V
PQ7 on the drain i got 19.5V on the source i got 18.7 V
Next Pq8 is connected to PQ7 Source to Source. and on the Drain of PQ8 i dont get any voltage.

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

its charging. dont bother it because your notebook not work

u have vin, so chceck 3.3VALW and 5V always

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

its charging. dont bother it because your notebook not work

u have vin, so chceck 3.3VALW and 5V always

Where should I check for 3.3v and 5v

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

search in schematic

[atsio]

Re: ACER ASPIRE 5517 burnt MOSFET

Let's start from the beginning. Stop searching for the 3.3v and 5V.
Remove PQ35.
What is the resistance relative to ground on all pads of PQ35?

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

pq35 is really the beginning

[atsio]

Re: ACER ASPIRE 5517 burnt MOSFET

Yes it is

[nearxos]

Re: ACER ASPIRE 5517 burnt MOSFET

Let's start from the beginning. Stop searching for the 3.3v and 5V.
Remove PQ35.
What is the resistance relative to ground on all pads of PQ35?

Drain to ground resistance: started measuring 900 kΩ and gradually decreased to 110kΩ

Source to ground resistance : 10Ω

Gate to ground resistance 234 Ω


i check for 3.3 V and 5V as advised earlier couldn't trace a 5V anywhere I did find a 3.3V on PQ13 but not on U41 according to the schematics

[ktmmotocross]

Re: ACER ASPIRE 5517 burnt MOSFET

chceck pl4 and pl5