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Apple Computing Products:
macOS - Notebook Hardware
My Covid MacBook Retina Project
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<blockquote data-quote="iggibar" data-source="post: 1848888" data-attributes="member: 97843"><p>After cleaning, I went to plug in the "clean" screen to test it. Andddd, it was a no go. Flashing a light behind the Apple logo revealed the screen was on, but there was no back light. I tested the "dirty" screen to check that out. Same thing. Then I took my current Late 2013 Retina and tested the screens on it. Worked great. Plugging its screen into the 2.2 also showed the same back light problem. These steps took about 30 minutes, but it was needed so that I wouldn't be sitting on 2 screens without definitively knowing if they worked, and it helped narrow down the issue at the same time.</p><p></p><p>Knowing that the backlight was not working is usually related to two common things-</p><p>1. The backlight fuse popped.</p><p>2. The LCD connector shorted.</p><p></p><p>It was time to pull out one of my favorite measuring tools-</p><p>[ATTACH=full]31459[/ATTACH] </p><p>This is a FLUKE T5-1000 volt meter. I have a few electrical testers, and some much more sophisticated, but I always pull this out first. It's simple, automatic AC/DC meter, and it's super easy and quick to use. I highly recommend it!!!</p><p></p><p>This is the LCD fuse-</p><p>[ATTACH=full]31460[/ATTACH]</p><p></p><p>To check the fuse, I connect the magsafe power and turn the MBP on. I place the ground probe of the FLUKE onto any I/O metal shroud, and place the red probe onto the end of the fuse. It should be around 12.5v. One side was, but the other showed 0 volts. That's a problem! A fuse should always have continuous voltage from one end to the other when the system is on. </p><p></p><p>To double check this, I tested for continuity by placing my FLUKE into continuity testing mode.</p><p>Continuity checks pathways of electrical flows by testing if current can flow between both FLUKE probes. </p><p>This is used to see where electrical paths have been broken, and is especially good when checking fuses.</p><p>A working fuse works by connecting connection A to connection B, and acts as a weak point should a voltage increase occur in order to protect connection B. If the fuse is overloaded, it pops first and saves the connecting components from burning. If a fuse pops, the FLUKE probes will not be able to flow current between either probes.</p><p></p><p>So, to test this, I placed both FLUKE probes on either end of the fuse. And surprise surprise- there was no continuity. To make sure there was no other short, I tested continuity from the fuse all the way down the LCD connecter #1- which is the line that carries the power to the LCD. There was no continuity.</p><p></p><p>I examined the LCD port, and tested to see if the #1 connection was damaged. When the backlight goes out, it's common to see the #1 connection to be completely melted. This one was perfect. I tried taking a picture, but my skills were lacking at the moment and everything was fuzzy.</p><p></p><p>Unfortunately, fuse don't usually pop on their own, and it's not 100% possible to know what caused it to pop without replacing it and giving it a run.</p><p></p><p>Good thing my 13" retina that I replaced the stock logicboard is a good parts donor<img src="data:image/gif;base64,R0lGODlhAQABAIAAAAAAAP///yH5BAEAAAAALAAAAAABAAEAAAIBRAA7" class="smilie smilie--sprite smilie--sprite8" alt=":D" title="Big grin :D" loading="lazy" data-shortname=":D" /></p><p>[ATTACH=full]31461[/ATTACH]</p><p>This is the LCD fuse I will be plucking out of it.</p><p>[ATTACH=full]31463[/ATTACH]</p></blockquote><p></p>
[QUOTE="iggibar, post: 1848888, member: 97843"] After cleaning, I went to plug in the "clean" screen to test it. Andddd, it was a no go. Flashing a light behind the Apple logo revealed the screen was on, but there was no back light. I tested the "dirty" screen to check that out. Same thing. Then I took my current Late 2013 Retina and tested the screens on it. Worked great. Plugging its screen into the 2.2 also showed the same back light problem. These steps took about 30 minutes, but it was needed so that I wouldn't be sitting on 2 screens without definitively knowing if they worked, and it helped narrow down the issue at the same time. Knowing that the backlight was not working is usually related to two common things- 1. The backlight fuse popped. 2. The LCD connector shorted. It was time to pull out one of my favorite measuring tools- [ATTACH=FULL]31459[/ATTACH] This is a FLUKE T5-1000 volt meter. I have a few electrical testers, and some much more sophisticated, but I always pull this out first. It's simple, automatic AC/DC meter, and it's super easy and quick to use. I highly recommend it!!! This is the LCD fuse- [ATTACH=FULL]31460[/ATTACH] To check the fuse, I connect the magsafe power and turn the MBP on. I place the ground probe of the FLUKE onto any I/O metal shroud, and place the red probe onto the end of the fuse. It should be around 12.5v. One side was, but the other showed 0 volts. That's a problem! A fuse should always have continuous voltage from one end to the other when the system is on. To double check this, I tested for continuity by placing my FLUKE into continuity testing mode. Continuity checks pathways of electrical flows by testing if current can flow between both FLUKE probes. This is used to see where electrical paths have been broken, and is especially good when checking fuses. A working fuse works by connecting connection A to connection B, and acts as a weak point should a voltage increase occur in order to protect connection B. If the fuse is overloaded, it pops first and saves the connecting components from burning. If a fuse pops, the FLUKE probes will not be able to flow current between either probes. So, to test this, I placed both FLUKE probes on either end of the fuse. And surprise surprise- there was no continuity. To make sure there was no other short, I tested continuity from the fuse all the way down the LCD connecter #1- which is the line that carries the power to the LCD. There was no continuity. I examined the LCD port, and tested to see if the #1 connection was damaged. When the backlight goes out, it's common to see the #1 connection to be completely melted. This one was perfect. I tried taking a picture, but my skills were lacking at the moment and everything was fuzzy. Unfortunately, fuse don't usually pop on their own, and it's not 100% possible to know what caused it to pop without replacing it and giving it a run. Good thing my 13" retina that I replaced the stock logicboard is a good parts donor:D [ATTACH=FULL]31461[/ATTACH] This is the LCD fuse I will be plucking out of it. [ATTACH=FULL]31463[/ATTACH] [/QUOTE]
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Apple Computing Products:
macOS - Notebook Hardware
My Covid MacBook Retina Project
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