Sidebar Sidebar
Become a MacRumors Supporter for $50/year with no ads, ability to filter front page stories, and private forums.

Identifying fuse on A1278 (mid 2010 13" MBP) Logic Board

E

ek13

macrumors newbie
Original poster
Nov 5, 2011
5
0
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.
 

Attachments

  • macbook-logic-board.jpg
    macbook-logic-board.jpg
    995.4 KB · Views: 39,044
Last edited:
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:
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:
https://forums.macrumors.com/threads/1122338/

----------

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

https://forums.macrumors.com/posts/16343697/
 
Solution for us !! :)

Sorry I haven't seen your message !!

Yeahh my MB have resurrected !!

Thankss
 
Last edited:
That's great! Can you tell me what it was or what you did? The link your provided is for the entire thread.
 
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 : https://forums.macrumors.com/threads/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:
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!
 
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.
 
zamirow said:
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
Click to expand...

Just passing A1278 schematic is here. http://podnutz.com/forums/download/file.php?id=638&sid=06fca7dd7a4b0c6b689a743d19e65fe3
 
zixu said:
Just passing A1278 schematic is here. http://podnutz.com/forums/download/file.php?id=638&sid=06fca7dd7a4b0c6b689a743d19e65fe3
Click to expand...

Thankss but now I'm using my MB with a Full Fan Noise for the moment....

----------
ek13 said:
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!
Click to expand...

Hey, I found something interesting :) For our dead MB :) ( Service Manual)

http://tim.id.au/laptops/apple/macbook/mb13_al_late08.pdf
 
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.... :eek:

On my Logic Board I have 4 pins for the regulator :)
 
Schematic Anyone?

Well if you didn't fix it, here is the file for it.
 

Attachments

  • LB# 820-2327 schematic diagram.pdf
    1.7 MB · Views: 10,652
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.
 
hi, when i do the trick of 10 sec the fan start turning but nothing else boot, the green light on the magsafe is green... there was water spill on it. somewhone gat some idea?
 
You must log in or register to reply here.
Register on MacRumors! This sidebar will go away, and you'll see fewer ads.
Top Bottom
Back