Help, what is this chip?

[gtyrrell1]

I have a 2010 13" macbook pro logic board with a bad surface mount chip.
The numbers on it are 7149 it is about a 1/4 wide chip square has
                                    AJ
                                  501C

It is right by the lvds 30 pin connector. I am trying to find where I can by one and what the real name of it is. It appears to control the voltage to the led screen

Any help is greatly appreciated.

I have attached two photos of it
Thanks
Gilbert

[chrome]

Why did you take a sideways picture of a screen?
Command-Shift-3, use it

[free_electron]

the logo is clearly siliconix ( S with embedded I  on middle line )
judging from the heat tab and the 4 pins on the other side my gues is a power fet or a linear regulator chip.

[free_electron]

Googling '7149 siliconix' gives me a SI7149 power P-mos. pulling the datasheet looks like a match. the package is correct.

tadaaa : http://www.vishay.com/docs/68934/si7149dp.pdf

[amyk]

It always surprises me when others say a part is "bad" when they don't even know what it is, and there's no obvious physical damage.

If it's the A1278 model there are only 2 SI7149 in the main power circuit for switching between battery/DCIN power.

[gtyrrell1]

 amyk:

I am brand new to all this stuff hence why I said "Bad". The chip actually has 2 missing fillets, the board got some minor liquid damage on it and currently it is creating the "curtain effect" on the screen. This is the only physical damage I see at this point. So i was not sure if I should just replace this chip or solder it again. Thanks to all for the info.

Gilbert

[SgtRock]

Greetings Gilbert (gtyrrell1):

--Welcome to the the forum. This is a great forum with lots of friendly helpful folks, and only a couple of stinkers. For your elucidation, you will find a couple of Sticky Threads in the General Chat section of the forum; 1) What's This Please, and 2) New Members Introduce Yourself.

--As you can see, one of our resident experts, free-electron, was able to read your screen photograph, and find the exact information you needed. Though he might have had to rotate the picture, which is not a difficult chore for an expert. Still I would recommend that, next time, you take a picture of the chip directly, if you can.

--If you do not yet have your own digital camera, I highly recommend you get one, with the highest resolution you can afford. You have not added your country of residence to your profile, so it is difficult to recommend sources to you. I have been buying high quality refurbished Digital Cameras from Geeks.com here in the USA, and have been well satisfied with the price and the performance. A camera is a must in any kind of complicated repair, automotive, electric or whatever. You can always figure out what you had before you started, and you can study the pictures in comfort and zoom in. Also, sometimes you can get the camera into places where you head will not fit, or does not want to go.

--With regard to the seeming hostile, badly punctuated, advice in the Imperative Voice, give it no mind, perhaps some of the post was lost and it was not as rude as is sounds. Someone here will be always be willing to help you, even with upside down pictures. Just thank you lucky stars you do not have to work for someone who talks to people in that fashion.

"All I wants of you, Cap'n Simmons, is plain seevility, and that of the commonest goddamndest kind!"
Zeph W. Pease

Best Regards
Clear Ether

[gtyrrell1]

Updated profile, thanks.
I am from US, any suggestions on where to get the chip?

[gtyrrell1]

Thank you so much! The chip actually only has two of the four pins soldered. When the liquid hit it, I guess it burned two off. The pads still look fine. Do you think it would be worth just resoldering what is there or just replacing it? Again, I am a rookie so forgive the simple questions.

[Monkeh]

Thank you so much! The chip actually only has two of the four pins soldered. When the liquid hit it, I guess it burned two off. The pads still look fine. Do you think it would be worth just resoldering what is there or just replacing it? Again, I am a rookie so forgive the simple questions.

Liquid would not randomly burn off two pins. So long as pins 1 and 4 are soldered, I doubt there's an issue with that chip.

[gtyrrell1]

Well, actually pin 3 and 4 are connected(according to the data sheet layout) and there is definitely a problem with power to the display. It lights up but gives a "Curtain Effect" at the bottom of the screen. So that's why I am looking at resolder or replacing the chip.
Can use all the advise I can get.

http://www.vishay.com/docs/68934/si7149dp.pdf

[Monkeh]

3 and 4 is also fine.

Please describe this 'curtain effect'.

[gtyrrell1]

How about a picture!

[Monkeh]

Half the LEDs aren't lit. That could, I suppose, be down to a missing connection at some package, but I don't see why they'd have them connected separately. I also don't see why the LEDs would require their own battery/line switch, which is what those FETs are used for.

I think, perhaps, you should track back the circuit from those LEDs and find an actual fault, instead of going 'hey, let's replace this chip because... well, because!'.

[gtyrrell1]

I will try, but I am not real experienced in tracing. Have access to the block diagrams, but not much more.

[SgtRock]

Dear Gilbert:

--Once again I concur with Monkeh. This being an Apple product, you will probably never be able to obtain a schematic. So as Dave Jones says "take it apaaht". There should be a dual power supply to the LED strings. Having a dual supply allows them to lower the voltage, as well as providing redundancy, albeit with a loss of quality. You may be able to try switching plugs to see if which string lights up switches as well. Trace the wires and tracks from the LED strings back to the dual power supply, take some pictures and post them. Should be a relatively simple fix. Since the LED PS wires bend every time the Laptop is opened or shut, it could even be as simple as a broken wire or a loose connector. Repeat, "take it apaaht", and take pictures as you go.

"I'll have the Alfalfa sandwich, and the smashed yeast"
Woody Allen 1935 -

Best Regards
Clear Ether

[amyk]

Actually you can find a schematic, if it is the model I think you have, look for the "MLB_LDO K6" This is possible for many other electronics too, you just have to do a bit of digging around on the Internet.

One thing I'd like to make perfectly clear: That MOSFET you identified is NOT the culprit of this problem. If it was defective, the entire machine would either run on adapter only or battery only, but not both.

The backlight has 6 series strings with an LP8545 as the driver. I don't know the pin configuration of the connector but if it has 2 sides then dirt on one side can cause this alternating pattern effect. Clean it.

Edit: found a picture of where the components are. The '7149 is in the lower right and isn't part of this circuit.

[SgtRock]

Dear Amyk:

--I tried searching as you suggested. I found numerous sites advertising the schematic for 10 to 14 dollars, but all illustrations were of block diagrams. They wouldn't advertise a schematic and then provide a block diagram, would they? This is a common scam with TV manuals, they advertise a schematic but all you get is mechanicals and block diagrams.

--If anyone knows where to get a guaranteed electronic schematic for this unit pleas post a link.

"Measure twice. Cut once"
Norm Abram 1950 -

Best Regards
Clear Ether

[gtyrrell1]

Found the schematic and attached a picture of the area with resistors and 24pin IC. Can't seem to get my digital microscope to take pictures right now so I am taking screen shots. I am guessing I need to test the resistors, however they are so small, I am not sure how to do that any suggestions? This is where the concentration of liquid was. Nothing went as far as the fuse. It appears that two of the pads coming off the 300k resistor are scorched leading to the IC, do not know if that matters.

Happy fathers day to all! 
I hope you all know how much I appreciate your wisdom and insight!
Amy, I agree on the other chip now that I understand the way it works from the diagram.

[SeanB]

Looks more like the liquid seeped under the IC and has corroded some of the tracks, and most likely the right hand side of the IC has had the connections eaten away. You will probably have to desolder the IC and clean under it. Difficult without the correct tools, hot air solder station and vacuum pickup tool.

[T4P]

Found the schematic and attached a picture of the area with resistors and 24pin IC. Can't seem to get my digital microscope to take pictures right now so I am taking screen shots. I am guessing I need to test the resistors, however they are so small, I am not sure how to do that any suggestions? This is where the concentration of liquid was. Nothing went as far as the fuse. It appears that two of the pads coming off the 300k resistor are scorched leading to the IC, do not know if that matters.

Happy fathers day to all! 
I hope you all know how much I appreciate your wisdom and insight!
Amy, I agree on the other chip now that I understand the way it works from the diagram.

1) SMD probe, very common ( Search DX for SMD probe, aliexpress also has it cheap or if you want quality UNI-T has it as UT-L06 )
2) Just use your probes, it's already on your board 
3) Some weird corrosive liquid got in ... man, what happened in there ( It's not that i like crApple devices ... i hate them, you asked for some help i gave you some advice )

[gtyrrell1]

1) SMD probe, very common ( Search DX for SMD probe, aliexpress also has it cheap or if you want quality UNI-T has it as UT-L06 )
2) Just use your probes, it's already on your board 
3) Some weird corrosive liquid got in ... man, what happened in there ( It's not that i like crApple devices ... i hate them, you asked for some help i gave you some advice )


What is "DX" and "UNI-T"

[alm]

DX
UNI-T

Both were the top Google hits for me, but I will resist the temptation of posting lmgtfy links.

[SgtRock]

Dear Gilbert:

--Now we are getting somewhere. Please see the below link for the data sheet for the TI LP8545 Backlight Driver:

http://www.ti.com/lit/ds/symlink/lp8545.pdf

--The block diagram on the data sheet can be misleading, as that is not the way the pins are actually laid out. For the actual pin outs, please see the attached picture from the data sheet. It seems possible to me that Amyk may indeed be correct and that the problem is dirt. If pins 16, 17, and 18 were being shorted to pin 15 by the conductive remains of a liquid it might produce the symptoms you see. I would try flushing with high purity isopropyl and trying to blow it out from under the chip using canned air. You could also use any good high volatility zero residue electronic parts cleaner.

--If you need to remove the SMD chip, I would recommend that you study some of the YouTube videos, showing how. They show you how to shield everything but the chip itself with foil. Also, you might want to consider the use of Chip Quick. You can find videos of Chip Quick use on YouTube also. You will need tweezers (preferably vacuum) that can pick the chip straight up, to avoid creating more problems with liquid solder. You will also need to learn how to clean the pads, and how to re-solder the chip in place. Dave Jones has some videos showing this, and YouTube does as well.

--And finally, would you please buy, beg, borrow, or steal a decent digital camera capable of taking a decent macro picture. Your pictures are, how do you say, for the birds.

"I wear suspenders and a belt. I am a security man all the way"
Justin Wilson (The Cajun Cook) 1914 - 2001
 
Best Regards
Clear Ether

[chrome]

How are you still taking pictures of your screen?

PROTIP: YOU CAN TAKE SCREENSHOTS AND SAVE THEM TO YOUR DESKTOP AND THEN UPLOAD THOSE.
Command-Shift-3, use it.