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Old Oct 18, 2012, 07:44 PM   #1
ek13
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Join Date: Nov 2011
Identifying fuse on A1278 (mid 2010 13" MBP) Logic Board

Hello,

Can anyone help identify the fuse circled yellow in the picture below? I am trying to diagnose the logic board and am not getting any resistance or continuity on that particular fuse.


It's a mid 2010 13" macbook pro (A1278) unibody I bought that had a spill. First time I connected it booted up and was working but very slow and battery was not charging. Now it's dead and I'm trying to diagnose it.
  • Magsafe connector is dim pulsating green
  • Magsafe adapter is 85W and good since it works another Macbook
  • tried reset SMC
  • disassembled and cleaned logic board using 99% Isopropyl Alcohol
  • tested resistance on all white fuses - ok
  • tested voltage on all white fuses (18.8v by DCIN connector and 0.8v close to battery connector)
  • tested continuity on logic board and DC IN board - ok
  • ordered a new DC IN board, hoping that's the cause.
Any help would be great.
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Last edited by ek13; Oct 19, 2012 at 12:18 AM. Reason: spelling mistake
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Old Dec 1, 2012, 12:44 PM   #2
zamirow
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Exactly the same Problem....

Hi ek13,

I have the same problem on my MacBook A1278 and my logic board is : 820-2327A 2008, and the Magsafe connector is dim pulsating green and nothing else...

I don't no what is the "yellow fuse" but Now I’m searching for a " MacBook 13″ Unibody A1278 schematic,SCHEM,MLB,M97 " but I didn't find it for the moment. It could help us to find what this component is!!

I made a test and shunted the Yellow fuse and pushed the power button but nothing...

I found the different tension than you, ~16v by DCIN connector and tomorrow I go to take on more time the tension on the DCIN and the tension near the battery connector.

Can you tell me when you receive your DC IN Board please !!

I continue to make some test and I tell you if something new!!

And if someone know this problem , please can tell us what are in default, it would be really nice

Thanks a lot

Ps : Sorry for my bad english....

Zamirow

Last edited by zamirow; Dec 1, 2012 at 12:56 PM.
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Old Dec 1, 2012, 02:38 PM   #3
ek13
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HI Zamirow,

I ordered another DCIN board from ebay and tried it but that didn't solve the problem.

You are likely getting ~16V at the DCIN board because you are using a 65W power adapter (mine is a 85W and hence, 18.5V). Chances are your DCIN board is fine.

I'm stuck right now with what else I can do to diagnosis the exact problem. I would like to find out what the readings on all the components should be also so I can figure out where the problem lies.

there is a long and informative thread that I've been following for help. Maybe it will be help to you:
http://forums.macrumors.com/showthread.php?t=1122338

----------

here is the way to measure and test your DCIN board:

http://forums.macrumors.com/showpost...postcount=1106
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Old Dec 1, 2012, 03:08 PM   #4
zamirow
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Talking Solution for us !! :)

Sorry I haven't seen your message !!

Yeahh my MB have resurrected !!

Thankss

Last edited by zamirow; Dec 1, 2012 at 03:13 PM.
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Old Dec 1, 2012, 03:13 PM   #5
ek13
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That's great! Can you tell me what it was or what you did? The link your provided is for the entire thread.
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Old Dec 1, 2012, 03:21 PM   #6
zamirow
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The procedure is : ( it's Temporaly procedure okay ?)

- With the magsafe disconnected press and hold the power button.
- While continuing to hold the power button plug in the magsafe connector.
- Continue to hold down the power button for 5 to 10 seconds.
- Release the power button and wait a couple of seconds.
- Now press and release power button. PRESTO!

Whole thread here : http://forums.macrumors.com/showthread.php?t=1122338

Thanks to my new God of the electronic: Dadioh

Z

----------


So now we know the SMC control circuit are in failure !! Also this method doesn't allow the mac to charge the battery!!

----------

Don't forget to put the RAM and the HDD !! and normaly the MB boot up and work fine !!

Last edited by zamirow; Dec 1, 2012 at 03:28 PM.
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Old Dec 1, 2012, 03:34 PM   #7
ek13
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That's one of the first things I tried too but my issue wasn't with SMC. I'll will update this post if I ever fix the issue. At least, you have your macbook back!
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Old Dec 2, 2012, 06:19 AM   #8
zamirow
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good luck ;)

Yess , I wish you good luck

Z
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Old Dec 2, 2012, 07:32 PM   #9
Nickepicke
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The component in the circle looks more like a ceramic capacitor in a 1206 package. If you are looking for a fuse, then look below the display connector in the picture, at the same height as the second connector on the right. A green component with the text "24 V", which is a thermally tripped resettable fuse.

From the picture it seems more likely that the black component on the upper left of the yellow circle is a part of the problem. That could a MOSFET and part of an input protection/regulation.
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Old Feb 14, 2013, 10:37 AM   #10
zixu
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Lightbulb

Quote:
Originally Posted by zamirow View Post
Hi ek13,

I have the same problem on my MacBook A1278 and my logic board is : 820-2327A 2008, and the Magsafe connector is dim pulsating green and nothing else...

I don't no what is the "yellow fuse" but Now Iím searching for a " MacBook 13″ Unibody A1278 schematic,SCHEM,MLB,M97 " but I didn't find it for the moment. It could help us to find what this component is!!

I made a test and shunted the Yellow fuse and pushed the power button but nothing...

I found the different tension than you, ~16v by DCIN connector and tomorrow I go to take on more time the tension on the DCIN and the tension near the battery connector.

Can you tell me when you receive your DC IN Board please !!

I continue to make some test and I tell you if something new!!

And if someone know this problem , please can tell us what are in default, it would be really nice

Thanks a lot

Ps : Sorry for my bad english....

Zamirow
Just passing A1278 schematic is here. http://podnutz.com/forums/download/f...9a743d19e65fe3
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Old Feb 14, 2013, 08:31 PM   #11
zamirow
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Quote:
Originally Posted by zixu View Post
Just passing A1278 schematic is here. http://podnutz.com/forums/download/f...9a743d19e65fe3
Thankss but now I'm using my MB with a Full Fan Noise for the moment....

----------

Quote:
Originally Posted by ek13 View Post
That's one of the first things I tried too but my issue wasn't with SMC. I'll will update this post if I ever fix the issue. At least, you have your macbook back!
Hey, I found something interesting For our dead MB ( Service Manual)

http://tim.id.au/laptops/apple/macbo..._al_late08.pdf
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Old Feb 14, 2013, 08:42 PM   #12
zamirow
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Hey ek13,

it's a picture of your Logic Board in the beginning of the thread ??

Because as Nickepicke said : " From the picture it seems more likely that the black component on the upper left of the yellow circle is a part of the problem. That could a MOSFET and part of an input protection/regulation. "

And in your picture I see the Mosfet with only 3 pins....

On my Logic Board I have 4 pins for the regulator
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Old May 18, 2013, 10:31 PM   #13
Chipmaster
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Schematic Anyone?

Well if you didn't fix it, here is the file for it.
Attached Files
File Type: pdf LB# 820-2327 schematic diagram.pdf (1.73 MB, 1218 views)
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Old May 27, 2013, 04:48 PM   #14
ek13
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Thank you Chipmaster, zamirow and zixu for the service manuals and schematics.

I had put off trying to diagnose the laptop after come up with no answers and didn't want to spend upwards of $250 on getting it repaired.

zamirow, I too noticed the the mosfet with the 3 pins after I initially cleaned the board. It looks connected but the soldering has come off. I was thinking of seeking out the specific mosfet, purchasing it online and taking to a circuit board repair shop to have it installed. Since I don't know what else to try, I figure it's worth a shot. I will post any findings or progress.
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