hi Can anyone tell me how to check mosfet shorting on laptop mobo.
Thanks sop-8 type
Thanks sop-8 type
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Last edited by scooby01; 01-28-2012, 11:34 AM. -
Re: How to check mosfet
There is a section in the guide at (this is how I test them)
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Re: How to check mosfet
I successfully repaired an Acer laptop with a shorted top MOSFET and 2 SMD capacitors in the CPU core supply, caused by failure of the controller i.c.
A few words of warning here, taken from my experience with this one. You can probably find the faulty FET in circuit, mine was shorted and tripping the power supply (brick). Removing it is not easy, the one I had the tab was soldered to the board for heat dissipation, it has to be pretty damn hot to get it off (I used a hot air reflow station at 450C for a good while, shielding the nearby areas with foil).
Out of circuit the MOSFET is extremely vulnerable to ESD, I destroyed one by accidentally touching the gate. Clearly a wrist strap is a good idea here. During a meter test I also thought I had another shorted one, as it gave a reading of around 30 ohms between 2 pins after testing twice (first test had been ok). It did return to normal though, I assume my meter biased the device to saturation and narrowed the depletion layer, which took time to recover.
I don't know much about FET's to be honest, but you can usually tell a shorted one. By the way, remove the CPU before doing in-circuit tests as it presents a very low resistance and could easily have you drawing the wrong conclusion.Comment
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Re: How to check mosfet
450*C is fine for defective part removal and board destruction but don't put parts back on with that high of temperature. I dilute all the pads with lead solder from my iron to drop the melting point. For TO-263 and TO-252 I heat the tab with the iron at 350*C and heat the pins with the heat gun at 300*C.
With some practice MOSFETs come off and go on quick and easy even in confined areas.
With the MOSFET out of the circuit it is possible to charge the gate with the DMM such that the MOSFET drain to source appears to be a short circuit.Comment
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Hello everyone, I recently found this badcaps site and super Learn Electronics Repair youtube channel. And I wanted to learn how to troubleshoot power supplies and VGA cards and how to practice soldering, since I already have a properly defective piece of them. I am currently trying to solve two problems:
I have a Gigabyte GV-RX460WF2OC-4GD type card. I managed to find the faulty MOSfet (AON6414A) on it, which I replaced. The card starts up, but after about half a minute, the MOSfet in the same position will be shorted again. Is it possible that the PWM controller driving the MOSfet... -
I've got an old Alienware M18x R1 which shorted out the charger whenever it was connected. Tracked down the short to two shorted caps and burned CPU power controller caused by a shorted mosfet on the CPU's graphic power supply.
I've replaced the faulty mosfet, two shorted caps and the CPU Power controller (NCP6151S52MNR2G).
Issue is now whilst there is no short if I attempt to power the system on the fans spin for a couple seconds there are no lights and no further action - the PCH is heating up but there is no CPU power coming out but there is an enable signal... -
I am trying to fix an iMac 2017 PSU, initially came with a blown fuse and shorted PFC MOSFET (6R199P). After visual inspection and some measurements I replaced the FET with a P20NM60 and tested with 100w series lamp, and it lasted 1 second before going into dead short. The PFC controller chip (NCP1605BG) and its passives appear fine (passives measure OK), but I do not know if there is a simple way of testing the NCP1605 as I wouldn't like to blind-replace it.
There was some slight blackening of the solder on the PFC controller passives so I reflowed them all with some flux. I am waiting... -
Hi All,
I have this MSI GTX-980ti Gaming Golden Edition. It had shorted mosfet on memory. Replaced the shorted i.e. Q47 PK616BA with 4C09N and the card ran fine for a month. Then suddenly again the same problem. This time when i replace it 4C09N or with replacement PK616BA (Aliexpress) it gets shorted. As soon as turn on the PC the PSU shuts down and the same mosfet Q47 gets short.
What should be the next step. Kindly guide.
The board view files for this gpu is available and attached. https://www.badcaps.net/forum/showthread.php?p=1237952... -
Hello.
Have this MSI Katana 17 MS-15851 that work only on battery with adapter and have first DC mosfet shorted. After replace not work without battery. On charger DC+ get power only for few seconds and it goes down...
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