Thanks to all who chimed in. Lol.
Anyways, everything is working fine now. I replaced the 6R199P with a ST 24N60M2 and put a slightly overspecced diode in place of the bad one. replaced the HDD with an SSD and i'm installing Mac OS now.
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Components arrived, I replaced the MOSFET and found a shorted diode (diode between PFC coil and MOSFET), replaced that too. The power supply worked fine for about 5 minutes, iMac turned on and worked, but the new diode (same model as original) went into short after that, and MOSFET may also be bad (did not remove and test yet, but it measured 250 ohms between drain and source in circuit). What could have caused this?Leave a comment:
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iMac 2017 PSU - shorted PFC mosfet
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 on new MOSFETs to try again.
I have also measured the two drive transistors for the PFC MOSFET as I read these could be the culprit (PMBT4401 and 4403 pair) and they are okay.
Any pointers as to what I should take a look at, before burning more new MOSFETs? Thanks
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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... -
Hi,
we've got iMac Pro 2017 which having a problem with SSD, iMac come with 2 SSD's 1TB, it was having a problem with the SSD so we get the replacement, installed in and iMac is stuck in recovery mode, tried to restore it & revive, nothing worked - error 4010. After installing old drives now we're having the same problem that the device is in recovery mode. Previously after swap of the SSD iMac worked on the old SSD however after attempt of revive on the new SSD machine stuck in recovery mode, I can go to DFU but the same result with error 4010.
Any ideas what might've... -
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... -
2017 iMac (Mid 2017) A1418
I'm not quite sure how this happened but a couple of components got ripped off the board when removing from the Logic Board from the iMac.
Can anyone help identify them?
I'll have to do the trace repair on the board before soldering on replacements but would prefer to order the components rather than get a whole scrap logic board off eBay.
Thank u
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I 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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