Question HP G3 450 Not changing possible short

[RoyalKem]

Hello and good day
My laptop is a hp g3 450, it was plugged in and charging some moments ago until my cat chewed on the AC adapter wire ( the DC part) and there was a little spark and the laptop went off, I quickly unplugged it as soon as it went off.
So far I plugged in my spare charger and it doesn't charge no more, the laptop powers on with the battery, I notice ed this after an hour and the battery was running low in stead of charging. It says its plugged in and charging and the charging amber indication is on, but once I take out the battery while plugged in, all lights go off. I checked the battery connector with a multimeter while plugged in and got no voltage and it doesn't power on.
Any ideas on what fix could work.
I have some experience fixing electronics.

 

[AlHuneke]

It is unlikely that shorting the charger output would damage the laptop. Actually, if the charger is well designed, shorting its output shouldn't damage the charger either. If it is an OEM HP charger, it should still be good. I would try to repair the short in the cable and see if it still works.

It sounds to me that the spare charger is not supplying enough current. Have you tried leaving the charger plugged in with the laptop off to see if it charges the battery?

 

[RoyalKem]

It is unlikely that shorting the charger output would damage the laptop. Actually, if the charger is well designed, shorting its output shouldn't damage the charger either. If it is an OEM HP charger, it should still be good. I would try to repair the short in the cable and see if it still works.

It sounds to me that the spare charger is not supplying enough current. Have you tried leaving the charger plugged in with the laptop off to see if it charges the battery?

I can assure you that the spare charger is great. I tried 3 OEM chargers and it didn't work so I had to open it up to Inspect the MB.
So it turns out a mosfet with chip id number B20N03 had blown a hole in the center. And I checked it with a multimeter, no current flow from source to drain.
I have basic knowledge about mosfet so I don't know where to go from here. My basic skills in electronics can get this fixed if someone points me out to it.

 

[AlHuneke]

Wow--That took a lot of current to do that! Obviously this part is bad, but you can't know if something else is also bad that caused this to blow. Without a schematic, it's hard to figure that out. A replacement is pretty cheap so worth trying. However, you would be working with surface mount parts which are difficult to work with. It may be wise to go to a shop that has the right tools and skills. I imagine that FET is the main power switching part, but without a schematic, who knows. I still find it weird that a short on the input could do this. It would be fun to see a schematic.

 

[RoyalKem]

Wow--That took a lot of current to do that! Obviously this part is bad, but you can't know if something else is also bad that caused this to blow. Without a schematic, it's hard to figure that out. A replacement is pretty cheap so worth trying. However, you would be working with surface mount parts which are difficult to work with. It may be wise to go to a shop that has the right tools and skills. I imagine that FET is the main power switching part, but without a schematic, who knows. I still find it weird that a short on the input could do this. It would be fun to see a schematic.

Thanks for your interest. Here is the schematics Hp G3 450 Schematics let me know what you think

 

[AlHuneke]

It doesn't open as a pdf for me. I just get an error. Did it open for you? I get an error that says it is a damaged pdf. Looks like you ran it thru some pdf maker. What was the original source?

 

[RoyalKem]

It doesn't open as a pdf for me. I just get an error. Did it open for you? I get an error that says it is a damaged pdf. Looks like you ran it thru some pdf maker. What was the original source?

I'm sorry, here is a link to pdf on gdrive
https://drive.google.com/file/d/107vI91RiaJUHJq3O28YidXwuIFVPGgQW/view?usp=drivesdk
Thank you

 

[AlHuneke]

It's great to get the schematic. I looked for the part number that is bad and found that FET used in seven places. Do you happen to know the part designator (such as PQ37) for the blown part? I may be able to poke around the design and figure out what would have blown due to a short on the power input from the charger, but I can't promise that.

I won't be able to pursue this until later tonight (about 12 hours from now). I will dig into it though as I'm curious as to what happened!

 

[RoyalKem]

It's great to get the schematic. I looked for the part number that is bad and found that FET used in seven places. Do you happen to know the part designator (such as PQ37) for the blown part? I may be able to poke around the design and figure out what would have blown due to a short on the power input from the charger, but I can't promise that.

I won't be able to pursue this until later tonight (about 12 hours from now). I will dig into it though as I'm curious as to what happened!

Thanks again for you time, I did a little study on the blown part, it an N-channel mosfet. Here is the datasheet for it
https://datasheetspdf.com/pdf/959832/ExcellianceMOS/B20N03/1

 

[AlHuneke]

What I got from the schematic. I don't know which FET is the blown one. Here's the places where the FET is used:

• Page 52 as the switching FETs used to create the battery charging current. +VIN I assume is right from the charger.
• Page 54 as the switching FETs (driven by the PWM power converter chip) to create +5VDC and +3VDC.
• Page 58 as the switching FET to create +VCCSA.
• Page 61 as a pass transistor to reduce 1.3VDC to 1.05VDC.

I can't tell from the schematic why that FET failed. It would be one of the switching FETs, I think. Don't see how shorting the charger could do that unless the battery charger FET fed a bunch of battery current back through PQ21 (but what turned the FET on to allow that to happen???). It may be there is a chip failure that turned one of the FETs on full time and blew it. Don't know what else to tell you.