HP laptop with no power. Can you help me understand the DA0R75MB6C1 schematics?

[mattpd]

Model: HP 17-e118dx
Board #: DA0R75MB6C1 REV C
Board Model: R75
Schematics: https://www.badcaps.net/forum/attach...7&d=1412835433

History: Unknown. Was donated with a shorted out USB port.

Problem: Will not power on. The only thing that happens when power button is pressed is a "pop" from the speaker. Damaged USB port has been removed.

This is my first serious attempt at board level repair (and using schematics) and I need a little guidance. The first thing I think I should do is check for voltages. I found the chips responsible for 3.3v and 5v on page 35 of the schematics. I have probed around, but can't find these voltages on the board so I think they are failing to produce voltage, but I want to be sure.

So my first question is, can you suggest a probe point for 3.3v and 5v from looking at the schematics?

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

Can't open the attachment.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

Can't open the attachment.

I couldn't either until I updated my WinRAR.

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

Maybe you could just rezip the pdf for us?

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

Maybe you could just rezip the pdf for us?

Sure. It's attached.

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

PU12 and PU13, what packages are they? Can you measure pin 1 (VIN)? If not you can probably measure on the adjacent inductor or ceramic caps.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

PU12 and PU13, what packages are they? Can you measure pin 1 (VIN)? If not you can probably measure on the adjacent inductor or ceramic caps.

They are tiny QFN so I can't probe their pins.

If I am reading the schematics correctly, I think I can get 3VS5 from the + side of capacitors 262, 263, 258, 256. And 5VS5 should be at the + side of capacitors 119, 120, 259, and 254. Are my assumptions correct? These voltages are not present, but I want to make sure I am not making a dumb mistake.

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

Check VIN first. Try to find on page 34 the FET PQ40.

It's a DPAK.

Measure the voltage on source and drain.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

Check VIN first. Try to find on page 34 the FET PQ40.

It's a DPAK.

Measure the voltage on source and drain.

Looks like about 19.5v on source and drain and 25v on gate. I forgot my digital meter so I am working with analog today.

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

From the source of this transistor it goes through PR234 (shunt) and the signal is named VIN. Can you confirm you have VIN at the PL15 and PL16 on both sides ? These are the inductors in series with VIN that go to pin 1 of the buck regulators for 3V3 and 5V.

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

And what is the voltage on the EN pin of PU12 and PU13? Try to probe on the resistor or capacitor next to it.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

From the source of this transistor it goes through PR234 (shunt) and the signal is named VIN. Can you confirm you have VIN at the PL15 and PL16 on both sides ? These are the inductors in series with VIN that go to pin 1 of the buck regulators for 3V3 and 5V.

I am having trouble locating either of them on the board. I found the labels for them, but I don't know what component they are pointing too. A "PL" is an inductor, right?

See attached pictures.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

Maybe this is PL15 (gray component next to pink capacitor)?? If so, I get 3ish volts on one side and 0 volts on the other side.

I still can't see anything near the PL16 label.

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

And what is the voltage on the EN pin of PU12 and PU13? Try to probe on the resistor or capacitor next to it.

Probe PC265 or PR241 for EN voltage on PU12?
And PC125 or PR151 for EN voltage on PU13?

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

I wonder if it's the right schematic. An inductor can look like PL20, the bigger component nearby or just like a SMD capacitor, only grey.

You need to find out if VIN goes to the chip. If it does you need to find out why it isn't switching, what the voltage on the EN pin is, or if the output is shorted elsewhere. What's the resistance from 3V3 and 5V to ground (with battery and DC power removed!) ?

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

Probe PC265 or PR241 for EN voltage on PU12?
And PC125 or PR151 for EN voltage on PU13?

Yes

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

I wonder if it's the right schematic. An inductor can look like PL20, the bigger component nearby or just like a SMD capacitor, only grey.

You need to find out if VIN goes to the chip. If it does you need to find out why it isn't switching, what the voltage on the EN pin is, or if the output is shorted elsewhere. What's the resistance from 3V3 and 5V to ground (with battery and DC power removed!) ?

I am able to confirm that VIN is 19v on both chips.

When you say measure 3v3 and 5v to ground, what pins am I measuring? The VOUT to ground on both chips?

[paulstef]

Re: HP laptop with no power. Can you help me understand the shematics?

I am able to confirm that VIN is 19v on both chips.

When you say measure 3v3 and 5v to ground, what pins am I measuring? The VOUT to ground on both chips?

You measure after PL20 and PL21 to ground, not directly from the chip to ground. Even though it wouldn't matter much if the inductor is ok because of its low DC resistance...

[meritosari]

Re: HP laptop with no power. Can you help me understand the shematics?

scan notebook
https://drive.google.com/folderview?...28&usp=sharing

[mattpd]

Re: HP laptop with no power. Can you help me understand the shematics?

scan notebook
https://drive.google.com/folderview?...28&usp=sharing

Very nice, thank you.