NP530U3C no power

[riki_22]

hi, i have this mainboard NP530U3C BA41-02156A BA92-11401B P06ABH LOTUS13-TSP , don't power on
i have checked the connector and it is ok.


I loaded the battery externally with it he turns on, but with only ac adapter no power please help me

i search a schematic and boardview but could not find them

[mcplslg123]

Re: NP530U3C no power

Start with msofets after dc jack. Whether gate is opening or not on those mosfets. Schematic helps but these are basic things which you can check without diagram as well. What is the charging chip?? You can download datasheet for charging IC and check as well.

[riki_22]

Re: NP530U3C no power

hi i don't find the mosfets after dc jack,

[SMDFlea]

Re: NP530U3C no power

hi i don't find the mosfets after dc jack,

Look at the connector where the DC jack plugs in.Try and follow the trace on the pcb from the red wires

[BlueMidnight]

Re: NP530U3C no power

Sometimes they send the power from the DC jack to some other random place on the board where the input FETs are located. In this case, the traces cannot be followed. Therefore, I suggest an alternate method.

On most boards, after the DC jack (and maybe some sort of fuse), there will be 2 FETs (or occasionally 1 FET and a diode) and then a current sense resistor. Find that resistor. Most boards only have 2 (the other one is in the battery charging circuit). They always have a low resistance written right on top of them and tend to look different than other resistors. So, they are not hard to find.

I can see both of these resistors in pictures I found of this board. Specifically, the AC adapter current sense resistor is on the back side of the board on the skinny part that sticks out (picture attached).

Follow the trace from that resistor to the nearby FETs. Then measure voltages on all pins of those FETs. Let us know the measurements and the part numbers of the FETs.

Posting a close-up and in-focus picture of this area would be very helpful as well.

[SMDFlea]

Re: NP530U3C no power

The fets could be in any place or opposite/nearby on the other side of the board.

[BlueMidnight]

Re: NP530U3C no power

When you glance at a board and want to find the input FETs, you can eliminate many possibilities right away. The large coils are part of buck regulators, and the associated FETs (or drivers with integrated FETs) must be as close as possible (for EMI reasons). Any 8-pin package that doesn't have 3 pins connected together on one side and 4 pins connected on the other is not a FET. Etc, etc.

There might be a few solitary FETs that are used as load switches, but it may also be clear what they are connected to.

Additionally, voltage regulator FETs are stacked facing the same direction. Input FETs are stacked facing back to back. In other words, the input FETs will have their sources connected together or their drains connected together.

I did forget to mention that there are usually one or more inductors after the DC jack as well. And it's not uncommon to see a bunch of small inductors in parallel rather than fewer, larger ones. So that's another thing to look for.

Taking all this into account, I was left with 3 extra FETs in the location indicated, which is the exact number I wanted to see, and a pretty good idea of which is which. But I needed a better photo to be sure. Which I now have (attached and annotated).