Are there fuses on the logic board?

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2009年中 MacBook Pro 13" 一体化机

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Kater @kater60017

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Are there fuses on the logic board?

Some background info:

I was asked by a relative to have a look at a Macbook Pro 13" mid 2009 that would not boot at all. It was "serviced" by a bungler after a water spill.

Upon inspection I noticed that one of the wires of the DC magsafe board was squeezed between a screw and the body and creating a short.

I fixed the short and the MBP booted and came to life again but the battery was not recognised and WIFI did not work.

I replaced the DC board, the battery, the battery indicator and the WIFI board without success.

Since the logic board was not completely fried by the short I wonder are there fuses on the logic board that protect certain parts of the board ?

Is there a fuse in the battery charge circuit ?

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Dan @danj

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Yes there are some fuse links, mostly to protect the graphics.

Given your problems your logic board was damaged from the spill. Did you find any corrosion or staining on it also where the markers red?

You may need to give the logic board a good cleaning as the corrosion could be effecting things. Otherwise it's time for a new logic board. Sorry :-(

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Thanks Dan, just to make sure I understand you correctly, there is no fuse in the power charge circuit and if the problems persist after a good cleaning there is no alternative for a Logic board replacement.

由 Kater 完成的 2015年8月7日

Unless you can troubleshoot down at the component level. Mostly what happens it the Mos FET transistors short out and/or the comparator logic gets damaged in the charging circuit. But you also have a problem with the WiFi which sounds like a deeper problem given the fact you switched out the AirPort card. Basically, this is a more advanced project than what most people can do (even me).

由 Dan 完成的 2015年8月7日

Hi Dan, I did clean the logic board on both sides where ever I could, so I don't think that is still causing problems. Further I think the WIFI and battery problems are not necessarily related. I have not replaced the WIFI/Isight cable which was suspect, as a quick fix I used a WIFI adapter. It is the battery problem that gives me a headache as it degrades the laptop to a desktop.

A new logic board will cost as much as a second hand MBP so if this problem can not be fixed, shopping for a second hand MBP with a sound logic board will probably be the best thing to do.

由 Kater 完成的 2015年8月8日

Sorry guy I think its time for a new logic board. I suspect the MOS-FET's are blown and maybe a few other components. Unless you have the needed tools and skills this is not something I would recommend trying to debug.

由 Dan 完成的 2015年8月24日

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Thanks Dan, just to make sure I understand you correctly, there is no fuse in the power charge circuit and if the problems persist after a good cleaning there is no alternative for a Logic board replacement. — Kater
Unless you can troubleshoot down at the component level. Mostly what happens it the Mos FET transistors short out and/or the comparator logic gets damaged in the charging circuit. But you also have a problem with the WiFi which sounds like a deeper problem given the fact you switched out the AirPort card. Basically, this is a more advanced project than what most people can do (even me). — Dan
Hi Dan, I did clean the logic board on both sides where ever I could, so I don't think that is still causing problems. Further I think the WIFI and battery problems are not necessarily related. I have not replaced the WIFI/Isight cable which was suspect, as a quick fix I used a WIFI adapter. It is the battery problem that gives me a headache as it degrades the laptop to a desktop.

A new logic board will cost as much as a second hand MBP so if this problem can not be fixed, shopping for a second hand MBP with a sound logic board will probably be the best thing to do. — Kater
Sorry guy I think its time for a new logic board. I suspect the MOS-FET's are blown and maybe a few other components. Unless you have the needed tools and skills this is not something I would recommend trying to debug. — Dan

zzz @zzz30021 声誉积分: 7.6千 zzz 13 22 11 · Answer 1 · 2015-08-07T21:22:32-07:00

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zzz @zzz30021

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Yes but no. Fuses never blow. Data line allowing battery to communicate with the SMC is another thing altogether, check with oscilloscope on data line end of R5280 & R5281. What do you see? Nice pulses? Does it go up to 3.42v and come down, or does it stop before it makes its way all the way up to 3.42v? If you use multimeter on diode mode and put red probe on ground and black probe on data line end of R5280 or data line end of R5281, what number do you get? 0.440-0.454 is normal, less and your data line is shorted to ground.

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Thanks zzz, I did my best to find an item on the logic board marked R5280 or R5281 but could not find them on either side of the board. Can you give me a clue, preferably a picture, where to find them ?

Then when I get abnormal measurements will it be possible to solve the problem ?

In the mean time I ran an ASD OS 3S132 and an ASD EFI 3S132 and all the tests where OK with the exception of the battery temperature sensor BT3T, but again a have no idea where to find the culprit.

由 Kater 完成的 2015年8月8日

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