Samsung board(bremen-ul) not powering - I think Ive found Short

[liamoc74]

Hey guys..

Got this laptop in, Samsung NP-R530, need help troubleshooting and fixing!!

Battery is dead..
Plugging in charger shows no lights..

Checked charger via multimeter and it shows 19V..

Stripped it down - plugged in charger and when holding one probe to ground and one to other pin on back of socket i get 19V - so the problem isnt DC socket.

The board is..
MODEL : BREMEN-UL
REV : 1.0(091123)-2

While charger is plugged in, i felt around top of board for heat and found the chip U507 to be very very hot, unplug charger and it cools..

I checked online for the schematic for the board and i could only find this..

http://service.sunc.org/resourses/service/schematics/sa...

I searched U507 and it seems to be part of the power circuit..
Now, im unable to understand the schematic and dont know where or what to do next, if anyone has any ideas or can guide me, id really appreciate it..

Thanks,
Liam

[khaahk]

Re: Samsung board(bremen-ul) not powering - I think Ive found Short

Schematic link is invalid.
From Bremen schematic seems that U507 is video ram chip. If it is, then it needs to be replaced and checked that anything else isn't wrong, because video ram should not be powered at such an early stage.

[liamoc74]

Re: Samsung board(bremen-ul) not powering - I think Ive found Short

Ok, this is the link im going by..



Ill check whats on the chip when i get in and see if i can find a replacement!

[Th3_uN1Qu3]

Re: Samsung board(bremen-ul) not powering - I think Ive found Short

Going by the schematic posted by the OP, U507 is RT8205A which is PWM controller for the 3.3v and 5v rails. If it failed, then yes, there is a pretty good chance that it will get hot and replacing it should solve the problem.

However, it can also get hot if there is a short on one of the LDO rails and it goes into current limiting - this is normal operation. Check for shorts on pins 8 (vreg3) and 17 (vreg5). With the board unplugged from power. Alternatively, with charger plugged in, measure on the small capacitors around the chip - you must find at least one 5v and one 3.3v. The 3.3v you will also find on the middle pins of the battery connector. If one of those voltages is missing or low, then it indicates there is a short on that rail somewhere, and not the PWM IC itself at fault.