Hp ZBook 17 G3 Not turning on sort of ???

[CraigR]

I have an hp ZBook 17 that will not turn on with the power button. I do have a charge light. I have the board out and the switch is good then I found something not making sense to me. A mosfet (see pic) has 19.9volt at the drain but nothing at source or gate HOWEVER if I touch the gate and ground with my bare finger I suddenly get power and can turn on the laptop with the switch and boots and runs fine. I did replace mosfet but same results. Not sure why the small resistance in my body to ground would get it going?

[mon2]

Re: Hp ZBook 17 G3 Not turning on sort of ???

What are the markings of your logic board ? Or if the schematics are available on this forum, link the page.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

Is this what you need? Also might not matter but that mosfet under the thermal camera was pulsating warm/cold over and over just with cord plugged in.

[mcplslg123]

Re: Hp ZBook 17 G3 Not turning on sort of ???

You need to probe charging IC.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

Don't know what one that is or what to look for.

[mon2]

Re: Hp ZBook 17 G3 Not turning on sort of ???

Near the mosfet that you touched - review the ICs. Most likely these 2 mosfets are close to the charger IC. Post the markings on the top surface of the part.

So far, unable to locate schematics for this logic board.

From the charger IC markings, the details of the charger circuit can be reviewed by checking other schematics or if we are lucky, the datasheet for the device (if it is public).

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

This is just left of the 2 mosfets. Not sure if it's what you want. Hard to read but top line looks like BQ next line looks like 24780S next TI 571 next AYZY

[mon2]

Re: Hp ZBook 17 G3 Not turning on sort of ???

That is the charger IC from TI. Datasheet is attached.

This logic board should be very close to the reference schematic showing on page # 36 (Figure 16).

If you have fine enough meter lead tips, consider to measure the voltage of each pin on this IC. Do so very carefully so that you do not short any of the pins.

Post the measurements for a review.

The datasheet can show you the pin locations and numbers.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

The readings were taken the same way I read the chip numbers so hopefully same as the pic.

[mon2]

Re: Hp ZBook 17 G3 Not turning on sort of ???

Can you confirm that you are on the DC VOLTS scale and using a setting 30V or higher?

The ACDRV reading looks proper -> this voltage is typically DCIN+6 volts = ~25v to ENABLE the first mosfet.

But you have many very low readings like Vcc = ~0 volts ?

VCC = the power rail to power this charger IC - can you confirm it again ?

Perhaps post a pic of your multimeter setting.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

Must have had bad connection on that one VCC 19.39v pic of my meter.

[mon2]

Re: Hp ZBook 17 G3 Not turning on sort of ???

great! nice choice of equipment We have the BEST hot air tool (clone of the QUICK) & same Fluke.

Remove all power, meter in resistance mode. Lowest resistance scale (2k is ok).

Check if the mosfets are defective with resistance checks between:

Source (1-2-3) & Drain (5-6-7-8)
Source (1-2-3) & gate (4)
Gate (4) & Drain (5-6-7-8)

of each of the 2 mosfets from your first post.

Checking for a low resistance = defective mosfet.

Post your resistance measurements.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

first starts at 225k and climbs but the other stays at 389k
Second OL on one and 450k on the other Third OL and .614m so guessing that first mosfet no good?

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

I think something screwey with my meter now all different readings

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

changed leads. The readings are correct now.

[mcplslg123]

Re: Hp ZBook 17 G3 Not turning on sort of ???

I'm bit baffled by the readings on BQ24780S. How ACDRV can be 24V without CMSRC being 19V and ACN/ACP also. I doubt the readings.

[CraigR]

Re: Hp ZBook 17 G3 Not turning on sort of ???

I'm bit baffled by the readings on BQ24780S. How ACDRV can be 24V without CMSRC being 19V and ACN/ACP also. I doubt the readings.

Possible as I was having issues with the leads when I checked it. New ones on now. I ordered that chip to try anyway.