On the logic board I can measure 5V and 3.3V only. Can you please let me know where other voltages are generated? What IC to check?
Thank you for help...
Jane
Senior Member
Last Activity: 03-19-2025, 02:03 AM
Joined: 08-02-2010
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HP ProBook 450 G2 (ZPL40-ZPL50-ZPL70 LA-B181P) does not start
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HP ProBook 450-G2 LA-B181P - What is a common resistance?
I have faulty [B]HP ProBook 450-G2 LA-B181P - [/B]doesnot start. When connecting a charger, the LED on plug in connector blinks from yellow to blue. (I tried to search a short on mainboard.)
What is a common resistance ( to ground ) I should measure on a coil that leads to VGA chip(RT8880CGQW) ? I measure only about 9.6 Ohms. Is it normal?I have faulty [B]HP ProBook 450-G2 LA-B181P - [/B]doesnot start. When connecting a charger, the LED on plug in connector blinks from yellow to blue. (I tried to search a short on mainboard.)
What is a common resistance ( to ground ) I should measure -
Can you please share the schematic?
Thanks -
I removed the USB loadswitch (U4305) and measured the resistance on VBUS rail like this
Input ( pin 3): 8.3M Ohm
Output ( pin 4): 0,16k Ohm
I guess there must be a short on the rail beyond the pin 4. What do you think?
What voltage and current should I use for testing via thermo camera ?
Thank you for help...Leave a comment:
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Lenovo E590
Lenovo E590 is shorted. With a thermocamera I found out hot IC U4305 and D4311 - please see in the picture enclosed - I circled them.
Do you think the culprit is IC U4305? Is it possible to bridge the ic ( from IN to OUT pins to be sure it is the culprit)?
What would you suggest?
Thank you for help... -
Thank you for the explanation....Leave a comment:
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Respond, how?...Leave a comment:
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What is the smartest way ?
Laptop ACER aspire 1 a114-32 (n17q4 ) has dark screen. If I push On/Off button the laptop seems to start ( including blue led light) but no picture.
What is the best way how to identify the reason? Whether is a culprit LCD panel or LVDS cable or mainboard ?... -
It might be an interesting point about PWM, but how much different the value will be ( if using multimeter)?Leave a comment:
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As far as I remember I did NOT solve the problem....Leave a comment:
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I measured PQ6.again
Gate&Drain 4.8M
Gate&Source 0.9M
Source&Drain 4.8M
I guess the PQ6 is good. Do you have any further solution ?
Thank you for helpLeave a comment:
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I removed PQ7. Yes , resistance increased e.g. Source-Drain was about 1.2M. But the gate voltage dropped to about 5V only.
Do you have any explanation for that drop?...Leave a comment:
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Here are results of resistance measurements
PQ6 Mosfet
Gate&Drain 1M
Gate&Source 0.32M
Source&Drain 0,9M
PQ7 Mosfet
Gate&Drain 0.8M
Gate&Source 0.28M
Source&Drain 0.66M
Are these values OK?
Leave a comment:
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Lenovo IdeaPad - mainboard ACLU5 ACLU6 NM-A281 Rev. 1.0
The laptop is dead. I can meaure only 19V rail.
Mosfets volatges: PQ6: Drain 19V, Source 19V, Gate 19V
PQ7 : Drain 0V, Source 19V, Gate 19V
Charging IC BQ24737:
Vcc 19V
ACOK 5.9V
ACDET 2.5V
REGN 6V
Do you think BQ24737 is faulty?
What should I check?
I enclosed a schematic.
Thank you for help... -
How do you test MOSFET in laptops ?
I tried to use this method:
Testing an N-channel MOSFET:
[I]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... -
Try this:
On PCB search IC fusb252umx ( it is under plate cover) near USB-C connector)
connect pin 3 with 12
and
4 with 11
[url]https://4donline.ihs.com/images/VipMasterIC/IC/ONSM/ONSM-S-A0013297909/ONSM-S-A0013297915-1.pdf?hkey=6D3A4C79FDBF58556ACFDE234799DDF0[/url]
And let us knowhttps://Try this:<br /> On PCB searc...4799DDF0[/url]Leave a comment:
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Did you solve the problem?Leave a comment:
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I flashed KA8G116A.rom but still no correct 5V_EN/3V_EN voltages.
I measured:
5V_EN is 3.28V
3V_EN is 0V
R3926: both sides have 0V
D2012: this diode is missing on the mainboard. Maybe someone else already repaired mainboard or is it a factory modifications?. Is it necessary to be there?
Voltages on D2012- pin 1 - is about 3.3V; pin 2 is 0V
Thanks again for helpLeave a comment:
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Thank you for your reply.
Yes, I successfully flashed SIO. But I do not know if the firmware was exactly right for my version of mainboard
I have DH5JV LA-G021P mainboard. Can you please let me know how to check( so that I know)if it is classic Acer thermal protection error? And how to repair it?
Thank youLeave a comment:
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Aspire 3 and KB9022Q (SIO) chip
I have a problem with +5V ALW and +3V ALW. These voltages are generated by RT6575 IC.
For correct function RT6575 needs 5V_EN and 3V_EN. These values are provide by KB9022Q chip.
I replaced KB9022Q and flashed, yet not 5V_EN and 3V_EN.
My question:
If there is no 5V_EN and 3V_EN , does it mean that I did not flash correct EC( embedded controller firmware) to that KB9022Q?
Or 5V_EN and 3V_EN does not depend on firmware running in KB9022Q?
Thank you for help...Last edited by Jane; 03-06-2024, 06:44 AM.
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