MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

first of all i wish everybody in this thread a happy new year.

but now back to my problem:

i got a hot-air station from a local dealer and some flux and kapton tape. but no matter how hard i tried, i did not get the solder to melt for a proper reflow. i tried tipping the side of the bga gently but it won't move.

@dadioh: what temperatures do you set on your station. and can you write down your procedure for a local reflow?

thanks in advance.

I set my hot air to 500 deg (highest setting it goes to). My station also adjusts the airflow rate and I set that around the middle setting. I want to make sure I don't blow small components out of place.

I tape off the areas around the device in question to shield them from direct heat as much as possible.

Before applying heat I apply flux to the contacts that I want reflowed. My flux dispenser has a needle tip so I can apply it underneath the BGA as well. I try and run it along the edge so that the flux wicks under the device. I then pre-warm the area by holding the heat up above the board about 6 inches and moving it around to get the general area heated up. I then gradually move in closer over a period of about 1 minute and then move the gun back and forth and circular motion around the area trying to get the heat up to the point of melting the solder. The first sign this is happening is when the flux starts to boil in the area and you can see some bubbling around the edges of the BGA. The amount of time it takes depends on the size of device but usually not more than a minute or two.

I then let it cool for at least 10 minutes or so before attempting to move the board to make sure all the connections are cooled and solidified.

Which device are you reflowing?

 

[naKruul]

I set my hot air to 500 deg (highest setting it goes to). My station also adjusts the airflow rate and I set that around the middle setting. I want to make sure I don't blow small components out of place.

I tape off the areas around the device in question to shield them from direct heat as much as possible.

Before applying heat I apply flux to the contacts that I want reflowed. My flux dispenser has a needle tip so I can apply it underneath the BGA as well. I try and run it along the edge so that the flux wicks under the device. I then pre-warm the area by holding the heat up above the board about 6 inches and moving it around to get the general area heated up. I then gradually move in closer over a period of about 1 minute and then move the gun back and forth and circular motion around the area trying to get the heat up to the point of melting the solder. The first sign this is happening is when the flux starts to boil in the area and you can see some bubbling around the edges of the BGA. The amount of time it takes depends on the size of device but usually not more than a minute or two.

I then let it cool for at least 10 minutes or so before attempting to move the board to make sure all the connections are cooled and solidified.

Which device are you reflowing?

i'm sill trying my luck with the WLED Driver of my early 2011 13" mbp.
25pin bga.
i contacted national semiconductors about this part. they stated that they produce the part for apple but did not provide further technical details maybe for a substitute.

 

[Dadioh]

i'm sill trying my luck with the WLED Driver of my early 2011 13" mbp.
25pin bga.
i contacted national semiconductors about this part. they stated that they produce the part for apple but did not provide further technical details maybe for a substitute.

Is it a BGA package? The previous models all used QFN packages for the WLED driver. The QFN's do have a thermal pad underneath them to conduct heat out of the part. That makes them a little more difficlt to remove but still you should be able to heat it enough to reflow the solder.

 

[naKruul]

Is it a BGA package? The previous models all used QFN packages for the WLED driver. The QFN's do have a thermal pad underneath them to conduct heat out of the part. That makes them a little more difficlt to remove but still you should be able to heat it enough to reflow the solder.

it is definetly a bga. i'll take a photo tomorrow, but beware, i already pretty ********* up that little sucker. but it still works, although i'm having trouble with the dimming. after the first reflowing attempts that dude at least works with the highest brightness and does not shut down anymore.
(i'm more and more getting the impression my backlighting problems are not a result of a failing wled driver)

 

[naKruul]

ohdear, now i totally ****ed up my logicboard... or at least the LED driver

reflowing worked like a charm with your procedure. unluckyly two balls merged together. i did not want to power on the board like this so i desoldered the chip completely.

this is what followed:

i don't know if this is the result of the coke spill or my bad soldering skills...

EDIT:

btw: i found out that the broken pins are one ground (rather unimportant) and the PWM connection which pretty much explains the dimming problems i think.

And i finally managed to find out which chip apple used: Turns out it's a relabeled National Semiconductors LP8550
I ordered 5 samples, hope they arrive soon...

 

[elektrosha]

Hello everybody
I have backlight problem, in my Apple MBP 15" core 2 Duo 2.4 GHz (A1226)
i tried to replaced my old LCD screen with a new one but i still have the same Problem
i think the problem is in an electronic part in the area inticated in the images which is damaged (burned) so please i need help to identify the part because there is no name,
Image
Image
like that one in the yollow square but it's not the same one ( Image from A1297 Motherboard )
i think it's a NAND gates but Am not sure...Thank you

The problem You are having might not be in backlight. Try Your A1226 on external monitor to make sure. A1226 had a recall on nVidia Graphic Chip. Laptop would turn on, but nothing shows up on the screen as well as on external monitor. If this is the case and Your MacBook Pro is under 4 years old - take it to the Apple Store and they will replace the logicboard free of charge. Hope it helps.

----------

Hey guys
Just a quick question
I have a macbook white unibody 2.26
machine was working perfect
I needed to test an lcd assembly so I hooked it up to the perfectly working machine and the lcd came on but just stayed white so i checked the lvds cable from the assembly and it had some broken/burnt pins so I hooked up the original assembly and I get the same thing, upon further inspection near the lvds connector on the logicboard I see that a component has blown
So can a bad lcd assembly with a blown lvds cable blow out a good logicboard?
I have included a picture from google and highlighted the component in yellow
Any ideas on what can be done,
I have a few dead boards but not the same model
Could I just bridge it?
Any help would be great
Thanks

Just wondering if You figured out the problem? I am having exact same issue. White LCD. External Monitor is fine. Please let me know what You ended up doing. Thanks!

 

[naKruul]

Holy cow! guess what, my macbook is back on duty

i ordered the samples from NS and it took only 2 days shipping from singapore to germany with UPS Worldwide express. Thanks National

only thing i experienced is: the new chip does not have dithering, so you see the dimming steps. but thats a flaw i can live with.

thanks Dadioh for your support. and if anyone ever needs a LP8550 do not hesitate to contact me. or otherwise just get some samples from NS

 

[PJonHar]

So I tried an external 24V supply on the screen itself but nothing! Upon further inspection with the multimeter the supply lines 38,39 & 40 were shorting to ground...HOW?

I took the LVDS cable outer off and found what looks like where apple have extended the LVDS cable by soldering?

I need to try and see the LCD side of the LVDS connector but really! don't want to remove the glass.

any thoughts?

 

[Dadioh]

Holy cow! guess what, my macbook is back on duty

i ordered the samples from NS and it took only 2 days shipping from singapore to germany with UPS Worldwide express. Thanks National

only thing i experienced is: the new chip does not have dithering, so you see the dimming steps. but thats a flaw i can live with.

thanks Dadioh for your support. and if anyone ever needs a LP8550 do not hesitate to contact me. or otherwise just get some samples from NS

Great news. So National only sells these to Apple and the only route is to ask for samples? I may try that if I ever need to repair a 2010 model.

----------

So I tried an external 24V supply on the screen itself but nothing! Upon further inspection with the multimeter the supply lines 38,39 & 40 were shorting to ground...HOW?

I took the LVDS cable outer off and found what looks like where apple have extended the LVDS cable by soldering?



I need to try and see the LCD side of the LVDS connector but really! don't want to remove the glass.

any thoughts?

Is the short happening within the cable assembly or in the LVDS connector on the logic board? I have had more than a few damaged LVDS connectors with stuff jammed inside them. Had to replace the whole connector.

Or are you saying the short is inside that cable assembly? From the looks of your photo it almost looks as if that line across the cables is meant to ground their shields? I think they may be using coax connections for signal integrity and EMI control. Where that line crosses was it somehow connected to ground? I have never peeled open the cable like that so I am just guessing.

 

[Dadioh]

Someone asked me about supplying 27V directly to the backlight on a MBP 15". I believe others on this thread have tried this and it works but I have not personally tried it myself. Anyways, for the benefit of those on the thread here is the location of the backlight voltage pins on the 15" MBP models which use a 40 pin LVDS connector. Note, the 13" use a 30 pin connector and pinout is different so please do not use this photo for 13" purposes.

 

[longcoo817]

i bought one of the dc dc step up board on ebay. Now heres the problem when i supply the 27v to the backlight it would show 0v and no voltage from the battery either. But when i remove it, its back to 27v again. there is no smoke or anything still powers up like normal. any help would be appreciated

 

[Dadioh]

i bought one of the dc dc step up board on ebay. Now heres the problem when i supply the 27v to the backlight it would show 0v and no voltage from the battery either. But when i remove it, its back to 27v again. there is no smoke or anything still powers up like normal. any help would be appreciated

Have you checked the resistance to ground on the backlight voltage pins? Sounds like they may be shorted to ground. That could be inside the lvds connector.

 

[longcoo817]

its showing .1 for resistance and there is continuity on the wires. I disconnected the cable and its still the same

 

[PJonHar]

Got the microscope out and checked if they were coaxial, you were correct!!

There is a shield wrapped around a tine black wire inside.

I tried to take a photo through the microscope with my iPhone.

I've peeled back the screen and will try again with an external supply.

Will post back the results in the week.

 

[Dadioh]

its showing .1 for resistance and there is continuity on the wires. I disconnected the cable and its still the same

Looks like there is a short to ground if you say you are measuring 0.1 ohms resistance to ground. The circuit that you bought on eBay may have some sort of current limit protection so it collapses to zero volts when you try to power the backlight. You need to find out where the short to ground is. My bet is on the LVDS connector itself.

 

[longcoo817]

That with the new lvsd cable I just replaced

 

[longcoo817]

Could it be shorted from the lcd board??

 

[bobbyt]

I have an A1181 white 13". Same story, water damage, backlight turns off one second after startup.

My board doesn't look the same as those posted. Where would I locate a fuse to test?

I should note when i plug in the power adapter the machine automatically powers itself on leading me to believe there's a short somewhere still but I'm left scratching my head. Need some guidance on where to examine.

 

[Dadioh]

I have an A1181 white 13". Same story, water damage, backlight turns off one second after startup.

My board doesn't look the same as those posted. Where would I locate a fuse to test?

I should note when i plug in the power adapter the machine automatically powers itself on leading me to believe there's a short somewhere still but I'm left scratching my head. Need some guidance on where to examine.

The A1181 uses a CCFL backlight and not LED. There is no fuse as far as I know. The CCFL requires a backlight inverter which is located in the hinge assembly behind the white plastic cover. On the A1181 logic board they generate a low voltage backlight voltage which feeds through a separate connector (not through the LVDS cable). You might have a bad inverter or the logic board may not be generating the backlight signal. It is a small 4 pin connector on the left side near the hinge when looking at your logic board. Check there.

 

[PJonHar]

So i connected on to the 3 supplies to the led's externally and the come on in different places when grounded to different returns, as they should.

When i put everything back together to try again, no picture comes up .

I havent a clue to what it could be i haven't messed with anything else apart from the supply lines. I am not getting the 3.3V on the LCD PWR (PP3V3_SW_LCD) though.

Any thoughts?

 

[Dadioh]

So i connected on to the 3 supplies to the led's externally and the come on in different places when grounded to different returns, as they should.

When i put everything back together to try again, no picture comes up .

I havent a clue to what it could be i haven't messed with anything else apart from the supply lines. I am not getting the 3.3V on the LCD PWR (PP3V3_SW_LCD) though.

Any thoughts?

I believe that 3.3V is what powers the panel itself. That should have 3.3V on it. If it doesn't then I suspect the SMC detects that and doesn't send the enable signal to the backlight power circuit. Check that 3.3V line and make sure it is not accidentally shorted to ground.

 

[longcoo817]

pjohnhar where did you hook up your grounds to??? also is your backlight working now?

 

[PJonHar]

pjohnhar where did you hook up your grounds to??? also is your backlight working now?

On the LVDS connector itself with a pin very carefully.

@Dadiho where can I check this 3.3v line? Is there a component I can check this off to make this easier?

Cheers.

 

[peislander]

I have an A1181 white 13". Same story, water damage, backlight turns off one second after startup.

My board doesn't look the same as those posted. Where would I locate a fuse to test?

I should note when i plug in the power adapter the machine automatically powers itself on leading me to believe there's a short somewhere still but I'm left scratching my head. Need some guidance on where to examine.

Where the inverter plugs in there are 4 caps & 3 0 ohm resistors in front of it.I had the resistor on the far right open on 2 different boards.Replaced the resistor & back light is back.Good Luck

 

[Dadioh]

Where the inverter plugs in there are 4 caps & 3 0 ohm resistors in front of it.I had the resistor on the far right open on 2 different boards.Replaced the resistor & back light is back.Good Luck

I think those are actually ferrite beads rather than 0 ohm resistors but that is for EMI emissions reduction. You could safely use a zero ohm and the only effect would probably be higher interference with other devices (but probably not noticeable)