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Model A1419 / Late 2012 / 2.9 & 3.2 GHz Core i5 or 3.4 GHz Core i7 Processor, ID iMac13,2

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Something is blown, I need help to identify component on logic board

Hello.

Story short … I’ve blown a few components near the LCD connector on the main logic board.

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I need to find the parts on ebay so that I can replace them.

From what I can find on YouTube and Google. It seems to be some kind of filter or a fuse (that I’m not so sure yet). From a thread on IFIXIT someone has similar problem and got help to identify the component as L4400 a 120 Ohm 3A fix inductor (ferrite bead). So I wonder if it is the same case for mine.

As it seems to be the cause that the LCD does not get power, and thereby CPU load of 100% and fan spinning non stop (source from youtube repair of similar case).

If you can point me to something I can buy on ebay or aliexpress I would really appreciate your help.

Thanks in advance.

Update (05/15/2019)

Multimeter Diode mode reading on one fo the pad

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Answered! View the answer I have this problem too

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3 Answers

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I changed the blown component (L4400 a 120 Ohm 3A fix inductor (ferrite bead)), which was ordered from ebay for 6 bucks, for a whole stack of it. I soldered (sloppy job, but well it was my first time) it to the logicboard and there were no more issue with the screen and fan.

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Hey I am having a very similar issue at the moment. Can you tell me the specifics of the fuse f4400? Maybe you can share the schematics with me as well?

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Most Helpful Answer

I think you will need to discover and correct whatever issue caused the components to blow in the first place, as well as trace out the whole path to verify that other components haven't also been damaged in a less-visible manner.

Schematics: http://schemalaptop.blogspot.com/2016/11...

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I wish I have the wisdom to do that kind of diagnostics. I'm working in the field of architecture and this is only a hobby. I'm still learning process. But thanks for the schematic. I might have better understanding of it later on. Right now I'm only in the proces of learning by trying through trail and error.

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Replacing a diode or resistor or something is generally easy enough, with a bit of practice. But component replacement without diagnosis means you're just shooting blindly in the dark. Consider: Let's say you locate, identify, and correctly replace the visibly damaged components but the computer still doesn't operate properly. There are no little signs waving out of chips that say "FIX ME!" so you'll need to perform tests. Knowing how to read a schematic and use a multimeter are the bread and butter here.

For example, you say "it seems to be the cause that the LCD does not get power". I would ask, how have you verified that? I'm sure that the blown component on the board is definitely causing a power delivery issue, sure, but have you verified that there's power UP TO that component? If there's not then replacing the component isn't going to help, AND it means you've got another issue to deal with.

I'm not trying to discourage you here, just prepare you for what needs to happen.

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Thien Khanh Nguyen were you actually able to download that schematic? None of the links worked for me ;-)

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Oldturkey03 yes I could get it from the first link on my iPad. And Steve you are right there is probably other issue. Story short this logic board is up and running to this step through help from this forum and YouTube :). I went from 1 LED light on the logic board to 3 there is probably a lot of issue ahead and I enjoy learning along the way, so bear with me. If you have literature for beginner to share on what I can read or where to look.

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Thien Khanh Nguyen  you are right about the component being L4400 a 120 Ohm 3A fix inductor (ferrite bead) . The next component right by it is F4400 or the fuse for the LCD power circuit. Power comes directly to it via PP12V_S0_LCD from the S0 rail. My suggestion is to clean the board check the fuse for continuity and replace the blown component after you check it with your meter between on of the solder pads and to ground. Use your meter in diode mode. Red probe to ground, black probe to a solder pad on L4400 and let us know what value you get. Then check with your meter in resistance mode and see if you have any continuity between the pads (red probe to pad and black to ground) and ground, which you should not have.

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It was exactly from your thread with another members that have the same issue, where I got this information and from Rosman group forum. I just didn’t know which is the fuse and which is the filter as they look the same, from my point of view. That’s probably where a schematic is usefull. I’ll try to do your step Lin the weekend.

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It took a while, but I had to purchase a multimeter and do some research on how to measure and understand what I measure. I have now clean up the board. I took the multimeter reading as instructed, but Iam unsure of the procedure is right. Diode reading I get: 0.432 V on of the pad (see picture) I dont get any results on the pad below.

Resistance reading: I don’t get any results, the multimeter just changes numbers up and down.

[image|1766260][image|1766261]

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Thien Khanh Nguyen will be eternally grateful.
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