koby058
Badcaps Veteran
Last Activity: 11-30-2025, 11:15 AM
Joined: 01-18-2017
Location: JERUSALEM
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what do you think about the voltage fluctuation (in the attached video) in the battery charging circuit?
it happens when no battery is connectedLeave a comment:
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battery voltage is only on the drain of the second mosfet.
before i had the leak in the second mosfet and i replace it, what else can it be?Last edited by koby058; 11-26-2025, 11:17 AM.Leave a comment:
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Hi and thanks for your help!
the resistance between 19 an 20 is 20 ohmsLeave a comment:
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Asus x1404za not charging
Hi
laptop works on charger and works on battery
pu8900 is bq24800
charge circuit Hi mosfet QH8902 was shorted from rain to source , when replaced the new mosfet got shorted immidietly when connecting charger
first and second mosfets are not shorted
When measuring voltage on the charging sense resistor the voltage fluctuate between 10.5 volt to 11.4 volt and after sometime it fixated on 3.42 volt Attached video
here is a boardview for thisasus board
https://www.badcaps.net/filedata/fetch?id=3700551
...Last edited by koby058; 11-25-2025, 08:01 AM. -
Yes, same message, using the normal power button or the novo N without holding it, will show it for a sec and turn off.
holding novo will show it for 20 sec and then try to boot or asking for boot device
https://drive.google.com/file/d/1pdT...ew?usp=sharingLast edited by koby058; 08-27-2025, 02:27 PM.Leave a comment:
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I have rewrite a new bios (two chips) and also rewrite the EC image using i2c with SUCCESSOR
My opinion is that the fact that the laptop working while the novo button is pressed (or shorted) maybe means it is not related to bios or EC firmware.
what do you think?...Leave a comment:
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On the power button i see 3.26v and go to zero when button pressed
just to make the current status clear: when i connect the laptop to AC without battery, the KB light and caps lock light is on, after a minute the laptop is going down and back up (probably it is the bios init process), when it turns on i can see the lenovo screen with some message that it is "finishing update do not power off" and immediately it shuts down.
when it is in this bios init process (without pressing the novo N button) i see the voltage on the power button fluctuating
...Leave a comment:
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mon2 i found out tha if i connect the daughter board the chargere is getting to 20v but the laptop powers on and shutting down
i found that if i press the SW1 whih is the novo n switch on the board the laptop turns on but if i stop holding the laptop shuts down, any advise?...Leave a comment:
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Hi,
3VSUS 1.75K
3VALW_TBTB​ 6.8KLeave a comment:
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due to a vacation i will update here only in the week after next weekLeave a comment:
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3VALW_TBTB 0v
VCC3_LDO_PD1 3.46v
VBUS_TBTA 0.15v
VBUS_TBTB 5.2v
+3VSUS jumping between 0 to 0.5v
could an corapted EC firmware cause this?Leave a comment:
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Yes, indeed the enable pins are also pulsing in the same mannerLeave a comment:
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i have shared a video. in the first post. is that good enough?Leave a comment:
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Hi and thanks for trying to help
on the 3.3v coil 5.87K
on the 5v coil 5.78KLeave a comment:
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yoga9 3v3 5v fluctuating
Hi
board model: NM-D992
type c remains on 5v. when i connect it the 3.3VALW and 5VALW fluctuating. can someone please help understand why?
main power rail voltage 13v
till now i have tried:
measured all coils resistance looks ok
replaced RT6585CGQW to a brand new one
replaced all mosfets for 3.3v regulator and the dual mosfet for 5v regulator
happen both on DC power and on battery
issue remains
video
schematic attached...Last edited by koby058; 08-03-2025, 09:23 AM. -
Any advise?...Leave a comment:
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Hi,
So, when i measured the main power rail i saw the voltage spiking between 13v to 15v so i have figured it is a voltage regulation issue
checking all related mosfet, i found another 2 N channel mosfets and another small one that got a bit of the water damage on the back of the board.
replacing it solve the issue, thanks a lot for the help!Leave a comment:
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Hi, I will only be there on sunday and i will check that.
I have found out that the laptop only works with battery connected and not charging
I am not sure if the laptop must have a working battery for it to work or it is indicating an issue
I will send the values next weekLeave a comment:
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