Dell Inspiron 6400 can't turn on

[gianttora]

Hello everyone,

I got Dell Inspiron 6400 from my friend. This laptop can't turn on. When i connected this motherboard to dc power supply it shows that voltage is decreasing and current is increasing. CC indicator also light up, so i think there is a short circuit on this motherboard.

One more thing is, fet (PQ6) is heating up so fast and extremely very hot. So i try to change the fet but the result still the same. Anybody can help me to solve this problem.

[gianttora]

Re: Dell Inspiron 6400 can't turn on

Anyone please help

[dj_ricoh]

Re: Dell Inspiron 6400 can't turn on

short on board!
did you took the board out?
pictures!
find the first fets test them

[gianttora]

Re: Dell Inspiron 6400 can't turn on

Thanks for reply,

Here is the pic of the DC regulated power supply which showing motherboard is short. My friend told when the voltage value is decrease, the current is increase and CC led is light there is short circuit on the motherboard.



And here is the pic of the motherboard where u can see the fet (PQ6).



Actually i'm not really sure how to test this fet. Should i connect this board to power supply and then test it. As I mentioned before when this board is connected to power supply this fet will become extremely hot in a short of time. I afraid it will burnt the fet and board too. So how do I test this fet in a right and proper way?

[fddizon]

Re: Dell Inspiron 6400 can't turn on

check fets near dc jack

https://cdn.badcaps-static.com/pdfs/...0f957c212b.pdf

[fddizon]

Re: Dell Inspiron 6400 can't turn on

check PQ42, PQ28, PQ22, PC144, PC145

[sasser]

Re: Dell Inspiron 6400 can't turn on

any caps around PQ6 was shorted . any caps when touch your finger hot?

[gianttora]

Re: Dell Inspiron 6400 can't turn on

check PQ42, PQ28, PQ22, PC144, PC145

Actually i'm not really sure how to test this fet. Should i connect this board to power supply and then test it. As I mentioned before when this board is connected to power supply this fet (PQ6) will become extremely hot in a short of time. I afraid it will burnt the fet and board too. So how do I test this all the component above in a right and proper way?

[gianttora]

Re: Dell Inspiron 6400 can't turn on

any caps around PQ6 was shorted . any caps when touch your finger hot?

I am not sure which one. I can feel nearby caps is getting hot but cannot specify which is it.

Can i take out fet PQ6 from motherboard and do the voltage test. What voltage value should i get when test it ?

[sasser]

Re: Dell Inspiron 6400 can't turn on

wait be patient. u must trace from leakage cap maybe around there. im not sure but when i face with this case my PSU Lab read increase up to 5.0Amp and im sure some caps was leak. so try to find out and test again pq6 is hot or not. if not try replce the caps

[gianttora]

Re: Dell Inspiron 6400 can't turn on

wait be patient. u must trace from leakage cap maybe around there. im not sure but when i face with this case my PSU Lab read increase up to 5.0Amp and im sure some caps was leak. so try to find out and test again pq6 is hot or not. if not try replce the caps

So u mean i need to find which caps was leak on this laptop motherboard and then clean them properly? Ok i'll try to find them.

[SteveHart]

Re: Dell Inspiron 6400 can't turn on

First thing you must do is to lower the current limit. Ussualy 1A is enough. After that you can search the component that is shorted by lightly touching the components directly connected to the 19v rails and find the one that becomes very hot. That component is the culprit. FETs, diodes, and caps are the most likely

[gianttora]

Re: Dell Inspiron 6400 can't turn on

check PQ42, PQ28, PQ22, PC144, PC145

I unable checking all the components u listed above because i afraid the mobo and fet (PQ6) will burnt. When connected this fet getting extremely hot within a couple of second.

[gianttora]

Re: Dell Inspiron 6400 can't turn on

wait be patient. u must trace from leakage cap maybe around there. im not sure but when i face with this case my PSU Lab read increase up to 5.0Amp and im sure some caps was leak. so try to find out and test again pq6 is hot or not. if not try replce the caps

I can't find any leak caps but when i remove PQ6 and connected the mobo to power supply here is the result i get.



Now no more components become too hot after i remove PQ6.

[gianttora]

Re: Dell Inspiron 6400 can't turn on

First thing you must do is to lower the current limit. Ussualy 1A is enough. After that you can search the component that is shorted by lightly touching the components directly connected to the 19v rails and find the one that becomes very hot. That component is the culprit. FETs, diodes, and caps are the most likely

Sir do you mean that i need to tune mannualy the Regulated DC Power Supply current value from 3.94A (pls refer pic in first post) to 1A. I already did that and found FET (PQ6) become extremely very hot just within a couple of second.

[dj_ricoh]

Re: Dell Inspiron 6400 can't turn on

if you replace the fet and still have the same problem you got a short on the board.
a cap its more likely because when you remove that fet you took out the rail so it wont be short.
this is a good thing if you plan to go forward like go to the next component and try to power until you find the broken part

[gianttora]

Re: Dell Inspiron 6400 can't turn on

if you replace the fet and still have the same problem you got a short on the board.
a cap its more likely because when you remove that fet you took out the rail so it wont be short.
this is a good thing if you plan to go forward like go to the next component and try to power until you find the broken part

Thank you sir for replying. Do i need to test the next component without resolder the fet back? What voltage should i get when test the other component?

[gianttora]

Re: Dell Inspiron 6400 can't turn on

When i look at the circuit diagram, I found a couple of component near the FET. I got FL2, PC22, PC20, PR16, PR21. I already did a voltage measurement without resolder the FET (PQ6) back. Here is the result.

FL2 - 18.95v, 18.95v

PC22 - 18.95v, 0.00v

PC20 - 5.59v, 18.95v

PR16 - 5.59v, 18.95v

PR21 - 0.00v, 5.59v

I also tested FET (PQ6) on motherboard

Pin 1 to Pin 3 - 18.95v
Pin 4 - 5.59v
Pin 5 to Pin 8 - 0.00v

So which one is the culprit ..?

[gianttora]

Re: Dell Inspiron 6400 can't turn on

When i look at the circuit diagram, I found a couple of component near the FET. I got FL2, PC22, PC20, PR16, PR21. I already did a voltage measurement without resolder the FET (PQ6) back. Here is the result.

FL2 - 18.95v, 18.95v

PC22 - 18.95v, 0.00v

PC20 - 5.59v, 18.95v

PR16 - 5.59v, 18.95v

PR21 - 0.00v, 5.59v

I also tested FET (PQ6) on motherboard

Pin 1 to Pin 3 - 18.95v
Pin 4 - 5.59v
Pin 5 to Pin 8 - 0.00v

So which one is the culprit ..?

Sorry i'm not testing the mosfet. I just test the mosfet point on the motherboard.

[SteveHart]

Re: Dell Inspiron 6400 can't turn on

Sir do you mean that i need to tune mannualy the Regulated DC Power Supply current value from 3.94A (pls refer pic in first post) to 1A. I already did that and found FET (PQ6) become extremely very hot just within a couple of second.

Yes, you should manually adjust the current. The reason that I ask you to limit the current to 1A is to avoid the FET (PQ6) getting too hot and broken while you search for the shorted component.

As dj_ricoh said, if you take out the FET, you just simply take out the 19V rail. Hence there will be no current flows to the rest of the circuit. So if the FET is measured OK outside the circuit, you can put it back in the circuit, and do the power supply test once again. This time try to find other components that becomes hot. That one is the culprit.