Hello everyone, I'm new to this forum so I'm hoping I do this correctly. Recently a family member's toshiba satellite c55d-a stopped charging the battery and could not be powered from the input. The battery powered the laptop fine and it worked fine. The supply seems to be working; outputs its 19V spec and so forth. So I took it apart and began probing around the charging circuit and found some things amiss:
First I noticed that USB ports output 3V-ish under load that spike up to 5ish every second.
Second the main power bus begins with 19V but at some point ends up looking like MainPowerSupply_2.jpg attached below (basically every second it resets to 5V and then builds up to the 19V only to reset again).
Lastly after further probing I found where the 19V turn into the intermittent 5 to 19V. I've attached Board.jpg (that squiggly line is the voltage wave form I'm getting on that power rail) which I have circled where the transition is made. It looks like those two ICs have something to do with it but I cannot find out what they are (mosfets maybe?); they are both the same IC and I labeled their orientation with a red dot. They are labeled: E4 GND 5P0712, which turns up no results for me. Anyone recognize it?
The bottom of the two ICs has 19V to gnd on the bottom, the top of the top IC has the strange varying voltage and in between, I'm not sure what is going on (no voltage or signal to ground) but the bottom IC has 15.3V across its bottom and top pins and the top IC having a varying voltage across its top and bottom pins (I cannot give specific details cause I cannot find a good point to reference my oscilloscope probe to and had to use a multimeter.
I cannot find a schematic anywhere online for this laptop as toshiba are very guarded with their schematics for some reason and I cannot replace those chips as I do not know what they are or if anything is even wrong with them.
So if anyone can help me I would really like to get the laptop working since it still worked with the battery (battery's dead now) and seems to only be a charge circuit problem. Thanks!