Released June 2012 / Core i7 processor with Turbo Boost / Up to 1 GB DDR5 Video RAM

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Where to find resistor responsible fan speed control

Here I've got motherboard with missing 2 components.

They are responsible for left fan speed control without them fan is spinning with one speed - I worry if I start using 100% CPU and GPU - chips will burn :(

...below Fan Connector

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...and here is how good motherboard looks like.

(showing resistor with engraved P is missing and black component)

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The chip which has a P on it is a fuse link for the fan. If you remember back in the day we had screw-in house fuses. back then when you didn't have a fuse you could cheat by using a penny to wedge into the socket. Boy! That was bad news back then better than 20 % of house fires where caused by people doing this!

So what does that have to do with your MacBook Pro?? Someone bridged the fuse in a similar manner using solder! Not good! If the fuse burn't there was a reason! So by defeating its function you put the rest of your system at risk.

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To start with you must replace the fuse here before you dig deeper. The other black chip is a resistor which looks like someone pulled up in the process of pulling the fan out.

@oldturkey03 - Do you have the specs for these components?

While you'er waiting for the parts, download the full version (payed) of this app: TG Pro its one of the better thermal monitoring apps out there. Lets see what it's telling us about the health of your system. Paste a full screenshot of the main display in an answer so we can see what you see as well.

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Thank You Guys for helping me :)

I've done Apple Service Diagnostics Test and everything pass well (apart of Waking Up things like Thunderbolt or SD Card) - so temperatures must be fine as it is Apple software (it is not the one where You start it with D key)

So where to look for those parts? How to name them?

About that P - is it the one? http://www.ebay.co.uk/itm/Macbook-Air-Pr...

Looks similar - but I've got backlight.

What about the small one? (so small it is barely visible naked eye)

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The fuse should be a backlight fuse..nothing to do with the fans. The board reminds me of a early or late 2011 i7 quadcore processor with standard lcd screen, not a retina..is it the 820-2915 ?

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Bart, I'm hoping our parts guru Old Turkey to chime in with the parts info.

I don't do component level repairs any more (eyesight just not up to it with small SMT parts), I also don't have the newer schematics for this system to pull the info from.

You'll need to wait till OT comes to the rescue here with the specs on the resistor & tell us if the fuse you found is correct ;-}

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Dan, if you ever need any schematics look at this website: apple-schematic.se

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Presuming it is a MacBook Pro 15" 2012 (non-retina, the board is definitely for a non-retina model), board number 820-3330;

Component under fan connector is R5650, 47K resistor, 5% tolerance, 1/16W in 402 package size. This being missing can definitely cause this problem.

Someone has bridged the fuse, undo this and solder a 3AMP 32V fuse in a 603 package to avoid problems in future.

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@reecee - Thanks Reece for filling in the details!

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@reecee thanks Reece! Bites to have to work for a living;-)

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I've bought this one - www.ebay.co.uk/itm/322392614992 (Backlight fuse SMD 0603 3A 32V Code P_

Will it be ok when I solder it?

Thank You guys for helping me!

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Yes, that fuse will be fine. You can get the resistor from Farnell, Mouser or Digikey

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@oldturkey03 - Sounds like May Day was a busy one ;-{ Sorry guy.

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Bart will be eternally grateful.
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