I recently bought this laptop to try to fix up because it was so cheap. It has no power so I figured it was a MOSFET or cap issue so I started with taking it apart, but when I had it apart I noticed one of the MOSFETs was missing. I'm new to this so I don't know where or how to look up what to replace it with. I do have the boardview for it so I somewhat know what was there which I attached ,and the missing piece is PQ303.
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Who is driving the mosfet? Can you identify the driving chip? Is it the charger IC? If yes, which is onboard and which pin is used to drive the mosfet? -
The gate pin(s) will have a resistor in series. Locate that part and confirm the resistor has a proper value. Always measure the resistor without power to the board. Often we see ~4k ohms on the series resistor. The other side of the resistor will go to the driver part. Draw a quick diagram of the path of this signal. Then we can study the driver component which may be the charger IC. We need to know which charger IC is onboard. We are doing this exercise to guess if the missing mosfet is a P-channel or N-channel type.
Post a pic of the missing mosfet area on your board. Are there any white silk screened text on the logic board for this missing part?Comment
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Here is the missing mosfetAttached FilesComment
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See attached. Remove all power. Meter in resistance mode. Measure the resistance between these 2 points of interest. We are checking if the mosfet to the left is being driven by the same gate voltage as the missing mosfet. If the resistance is ~0R ohms, then yes. Pour some IPA (alcohol) onto the small mosfet to the left and share the top side markings. This mosfet will reveal if we are dealing with N-channel or P-channel mosfets.
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It say QN3103 and measures 6.3 at 20k ohmsComment
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It appears that the same signal that drives the small mosfet is driving this larger mosfet with the 6k3 ohms resistance.
QN3103 is a N-channel mosfet so we should be fine to apply a larger sized mosfet to fit onto the PCB. The larger mosfet appears to be a common 5x6mm mosfet. You may have suitable parts on any donor motherboard OR you can order fresh ones from Digikey / Mouser. DK / Mouser will offer higher grade, branded mosfets with higher specs for the current support, etc.
Basing this on past motherboard designs but you should be safe to install a N-channel mosfet here. Just my disclaimer.
Let me know if you wish to buy a new one or check your motherboards for a donor. Start with a 5x6mm sized mosfet. Then share the topside markings. We need to check if it is N-channel type or not.
Last edited by mon2; 07-30-2025, 01:10 PM.Comment
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I'd probably be better off buying a new oneComment
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If you have a micrometer -measure the PCB pads for the width from edge to edge but appears to me to be the 5x6mm mosfet will fit fine here.
Here is a very good fit:
https://www.digikey.com/en/products/...4TRPBF/4502037
So pins 1-2-3 = source. Pin 4 is isolated and is the pin you measured.
Pins 5-6-7-8 are the drain group. Just be sure to place pin #1 onto the source pin #1 and the rest will align fine. Flux and solder onto the PCB pads.Comment
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Alright I'll order that and I'll update when everything is doneComment
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This MOSFET is the low side MOSFET for VDDCR_SOC, if someone attempted to power on the board with that MOSFET removed, it's very likely you have a dead CPU, as the 2 small MOSFETs next to it (PQ302 and PQ304) sent 19V straight to the CPU when powered on
Part number: QM3962M6
Use this schematics as reference, that section is similar to DA0NJFMBAD0:
https://www.badcaps.net/forum/docume...tic-board-view
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Hey guys,
i have a asus motherboard here and as the title says after the first mosfet (in the picture) there is nothing more than 3.15v.
I injected 19v and max. 1 amp at the charging port and there is not voltage drop or smth. It's just taking 19v and 1 milliamp.
Then i tried to inject 19v and max 1amp after the current sensor and there it first takes 19v and 4 milliamps and after 2 seconds it is taking nothing (no current).
I measured on the coils on board everything seems fine. Also the main power rail is not shorted (infinite resistance).
Now i thought something... -
I have an Asus GA502D, it had a blown mosfet which I replaced and the laptop booted into windows, a few mins later it shut off, the same mosfet was blown. I thought maybe just a bad mosfet but same thing happened again, a few mins in windows and shuts off.
I have removed the mosfet and can run the laptop no problem
The MOSFET is FDPC5018SG
Can anyone point me in the direction of what could be the cause of this, could it be the controller rt3663bc?
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I am trying to identify a potential missing component from an Asus X570-P motherboard. I could not find a boardview for that exact motherboard, but I did find one for the X570-Pro here https://www.badcaps.net/forum/troubl...prime-x570-pro
The component missing on my board I believe is a small 3 pin device above the Nuvoton Super IO. The X570-Pro uses a similar Nuvoton and there's a similar looking SMD just... -
Can someone please help me.. Mosfet is missing on this motherboard (Lenovo L340-15IRH) I cant find the part number.. Can someone please send me a picture or part number of the mosfet missing on the board.. Thankyou! -
ASUS STRIX G531GT MISSING PM_SLP_SUS#
Hello guys i have ASUS laptop that power on but can't switch ons , i trying using power sequence and last missing PM_SLP_SUS# .
here what i measure already:
EC_RST# 3.3V
SRTCRST# 3v
+3VA_RTC 3V
RTCRST# 3V
ME_SusPwrDnAck 0V
AC_PRESENT 3.3 V
AC_IN_OC# 0V
PS_ON 3,3V
+3VA_DSW 3.3V
DPWROK_EC /R 3.2V
PM_BATLOW# 3.3V
SM_INTRUDER# 2.8V
PM_SLP_SUS# -----> MISSING VOLTAGE ( but sometime this voltage is present )
THat is can confirm PCH relate issue...05-28-2024, 01:30 AM
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