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?
Hp ZBook 17 G3 Not turning on sort of ???
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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).Comment
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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.Comment
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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.Comment
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Re: Hp ZBook 17 G3 Not turning on sort of ???
great! nice choice of equipmentWe 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.Comment
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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.Comment
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Re: Hp ZBook 17 G3 Not turning on sort of ???
Possible as I was having issues with the leads when I checked it. New ones on now. I ordered that chip to try anyway.Comment
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by JaneI tried to use this method:
Testing an N-channel MOSFET:
Step 1: Discharge the Gate (turn off the MOSFET)
Place the black probe (COM) on the Source (S) and the red probe on the Drain (D). The multimeter should show no continuity (high resistance or "OL" – open line).
Then, touch the black probe to the Source (S) and the red probe to the Gate (G). This discharges any stored charge in the Gate, turning the MOSFET off.
Step 2: Charge the Gate (turn on the MOSFET)
Now, place the red probe on the Gate (G) and the black probe on the...09-27-2024, 03:31 AM -
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