MacBook Pro Unibody - No Backlight - Logic Board Question

[Kiowa]

No backlight - late '08 A1286

I've not had any luck with this machine.

A liquid spill killed it and forced a logic board replacement. I found a replacement on eBay which the seller claimed was from a working MBP with a broken LCD. I just found out that the broken LCD was from a drop. Bad news, since I've been reading that drops have a tendency to kill the backlight circuitry. Exactly what my problem is now...

Anyway, the machine boots fine with the new logic board and displays an image. I just have no backlight. The LVDS cable is unharmed with no signs of corrosion or burning and the display assembly is causing no problems (I swapped it out with a known working replacement and the issue still exists). I'm sure it has something to do with an individual component on the circuit board. I've looked through this thread and at all the photographs, but haven't seen anything that looks like what I have. I'm really hoping I can get some guidance here as there does seem to be a ton of knowledge on this particular problem.

Thanks for the help, everyone.

David

 

[osila]

Hello everyone I'm new here and I need help

I have a Macbook A1278 mid 2008 pouring water on it and it burned the cable of the screen I replaced the cable but there is no lighting on the screen I see the menus but there is no lighting
I saw that I need to replace the diode and the transistor 125 back if it does not work then there is the card's driver problem.




A. Can I just replace the diode 125 without replacing the transistor behind?

B. How do I measure exactly 27V? (I should be measured with a voltage)

You can specify how?

Thank you all

 

[Dadioh]

I have a Macbook A1278 mid 2008 pouring water on it and it burned the cable of the screen I replaced the cable but there is no lighting on the screen I see the menus but there is no lighting
I saw that I need to replace the diode and the transistor 125 back if it does not work then there is the card's driver problem.

A. Can I just replace the diode 125 without replacing the transistor behind?

B. How do I measure exactly 27V? (I should be measured with a voltage)

You can specify how?

Thank you all

First thing to check is the fuse. It is unusual for the diode to be bad.

To measure for 27V you need a multimeter with very fine tip probes. Set the meter to read DC Volts. You place the black end on a ground (usually one of the screw attachment points) and the red end on the point you see in the photograph. If it is a digital meter you will read the voltage as digits on the screen. If it is analog then you need to read the needle on the appropriate scale. Google multimeter measurement methods and you should find a guide somewhere.

Good Luck

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I've not had any luck with this machine.

A liquid spill killed it and forced a logic board replacement. I found a replacement on eBay which the seller claimed was from a working MBP with a broken LCD. I just found out that the broken LCD was from a drop. Bad news, since I've been reading that drops have a tendency to kill the backlight circuitry. Exactly what my problem is now...

Anyway, the machine boots fine with the new logic board and displays an image. I just have no backlight. The LVDS cable is unharmed with no signs of corrosion or burning and the display assembly is causing no problems (I swapped it out with a known working replacement and the issue still exists). I'm sure it has something to do with an individual component on the circuit board. I've looked through this thread and at all the photographs, but haven't seen anything that looks like what I have. I'm really hoping I can get some guidance here as there does seem to be a ton of knowledge on this particular problem.

Thanks for the help, everyone.

David

I think there are some pictures somewhere in this thread to show where the fuse is for the A1286 MBP15. Going from memory it will be on the back side of the board near the LVDS connector. Look for the small 0402 size component beige with a white dot on top. Replace the fuse and if it blows again then you need to find out where the short is.

 

[Lugnut2k10]

Is it also easy to get the keyboard lighting working again?

 

[Dadioh]

Is it also easy to get the keyboard lighting working again?

On the MBP15 the keyboard backlight connector is a 2 pin flex cable that attaches near the left fan. Check to make sure the flex cable is installed correctly and the latch is down and engaged.

 

[Lugnut2k10]

On the MBP15 the keyboard backlight connector is a 2 pin flex cable that attaches near the left fan. Check to make sure the flex cable is installed correctly and the latch is down and engaged.

And if the cable is broke, can i order a new one?

 

[Dadioh]

And if the cable is broke, can i order a new one?

It is integrated into the keyboard backlight so you need to order the whole thing. But they are not that expensive on eBay. Make sure you get the right one. The 13" backlight cable is in a different place.

 

[ijme]

.

.

 

[Dadioh]

Thank you, Dadioh, for starting this thread, and continuing to contribute, answer, support. You da man!

Like most posters here, I too have a dead backlight on an otherwise working machine: Late 2009 2.26 MacBook unibody.

The fuse seems to be ok. These others (boxed in red), don't have continuity, but I don't know if these have anything to do with it.

With my cheapo multimeter set at 2000 OHM, black probe on ground, I got these readings from the (?) WLED driver (MC34845/4HRKAE). I'm guessing it's fried.

Please let me know if I'm on the right track.

Again, thank you, Dadioh! And to all the helpful posters, my thanks as well.

I personally have never worked on the polycarbonate unibody and they use a different WLED driver than the aluminum so I probably won't be able to provide much relevant info. If anyone else with a working logic board can document the impedance to ground on the pins of that WLED driver that would be a good starting point.

 

[Richard-m]

With the LVDS cable out, it was pretty obvious what the problem was. I have attached a photo. The high voltage pins are all burnt out. The socket on the LCD panel is also a mess around those pins, so I think it is going to need both a new LCD screen and LVDS cable.

With a new LCD screen and LVDS cable, the display worked and the MBP 15 (2009) seems to be working fine. One thing I have learned is that if a good screen is not detected, the circuitry to supply the high voltage for the display is not enabled. So you need to know you have a good screen before chasing display voltages on the logic board.

 

[Dadioh]

With a new LCD screen and LVDS cable, the display worked and the MBP 15 (2009) seems to be working fine. One thing I have learned is that if a good screen is not detected, the circuitry to supply the high voltage for the display is not enabled. So you need to know you have a good screen before chasing display voltages on the logic board.

Excellent point! I always keep a test screen on my bench for this purpose. But a very good point for those of you troubleshooting your own machines with no spare parts.

Congrats

 

[eagandale4114]

If you just had your mac repaired and the backlight is not working go check with your store. The guy who serviced mine forgot to plug the cable in when he changed the part.

 

[iDutchman]

Hi all,

I have a 2010 2.4Ghz 13" MacBook Pro.

The screen works but no backlight (only in bright light visible). I have put a 2008 Macbook Aluminium screen onto the MBP and the same problem persists! Still no backlight.

So, now the original MBP screen is on here.

What can be the issue? Which fuse or WLED driver needs to be replaced and where are they located on mine? Thank you!

Also, could I use chips from the 2008 Late MacBook Aluminium logic board to get the backlight working again? The logic board is dead due to liquid spill. But a big chance the backlight component works?

THANK YOU!

 

[Dadioh]

Hi all,

I have a 2010 2.4Ghz 13" MacBook Pro.

The screen works but no backlight (only in bright light visible). I have put a 2008 Macbook Aluminium screen onto the MBP and the same problem persists! Still no backlight.

So, now the original MBP screen is on here.

What can be the issue? Which fuse or WLED driver needs to be replaced and where are they located on mine? Thank you!

Also, could I use chips from the 2008 Late MacBook Aluminium logic board to get the backlight working again? The logic board is dead due to liquid spill. But a big chance the backlight component works?

THANK YOU!

I "think" the fuse for the 2010 13" is in the same place as the 2009 model. There are some pics earlier in the thread that show the 2009 location.

The 2008 MacBook uses a different WLED driver so that part won't be of use but it does use the same fuse although it is in a different location. The problem with trying to reuse a fuse (hey that rhymes is that fuses are thermal devices so if you use too much heat removing them you blow them. I would just use a new fuse.

 

[iDutchman]

Thanks for responding so quick! Unfortunately, I really have no soldering experience/skills/tools whatsoever. So, I will not be able to fix this.

Does anyone know how I can get this thing going again. The machine is in mint condition and just over a year old.. (15 months).

Anyone knows good places to go to in Amsterdam or something?..

 

[iDutchman]

Also, a few pins seem really dark on the LVDS connector. Although, the display does get power and displays data. See pic for the details.

Sorry for the crappy quality, but I guess the iPhone 4S does not handle these conditions really good.

 

[russthechamp]

I hope I a not hijacking this thread, but I have a logic board issues that maybe some of you could help me with.


I picked up a used late 2008 macbook pro off ebay, and the owner reported the wifi wasn't working. After inspecting the logic board I found the following burned out area next to the airport connector.

I was hoping I could replace these components to see if I could get it up and running. Can anyone tell me what these components are resistor, capacitor etc , and where I might be able to get replacements?? Any advice would be appreciated.

Thanks
Russ

 

[Dadioh]

Also, a few pins seem really dark on the LVDS connector. Although, the display does get power and displays data. See pic for the details.

Sorry for the crappy quality, but I guess the iPhone 4S does not handle these conditions really good.

Those are the pins that carry the 27v to the backlight. Because of the higher voltage, in a liquid spill they corrode faster than everything else. You may be able to scrub off the pins with a clean toothbrush and 99% pure isopropyl alcohol. Then examine them under a microscope if you can.

There is a good chance that you will need to replace the connector.

----------

I hope I a not hijacking this thread, but I have a logic board issues that maybe some of you could help me with.


I picked up a used late 2008 macbook pro off ebay, and the owner reported the wifi wasn't working. After inspecting the logic board I found the following burned out area next to the airport connector.


Image


I was hoping I could replace these components to see if I could get it up and running. Can anyone tell me what these components are resistor, capacitor etc , and where I might be able to get replacements?? Any advice would be appreciated.

Thanks
Russ

Those are the devices that bring 3.3v power to the wifi card. Probably will work again if you replace them if the original fault that caused the issue is cleared.

 

[russthechamp]

Thanks for the info Dadioh. DO you happen to know what these components are? It looks like I am missing a black one and the orange one on the right looks fried? I have the schematic but I can't make heads or tails of it? Can you help me parse this infomration

 

[Dadioh]

Thanks for the info Dadioh. DO you happen to know what these components are? It looks like I am missing a black one and the orange one on the right looks fried? I have the schematic but I can't make heads or tails of it? Can you help me parse this infomration

Image

I am traveling now so just a quick answer. The missing black component on the right is probably the inductor. This is the middle inductor in the PI filter in the schematic. As a quick test you could short the pads to see if that restores wifi function. Best to replace it if you can since electromagnetic emissions would be higher without the filter. Do you have access to a spare parts board?

 

[mmaier]

Anyone in the Greater Toronto Area who can resolve a 300k and fuse issue?

I have been following and reading through all the great info on hear to repair my own 2010 13 inch Unibody MBP....however i think this is a little above my pay grade. is there anyone who has done or does these repairs in the toronto area? from my testing it appears the fuse is blown and the 300k resistor isnt working, since it doesnt measure...the WLED appears to be ok, as it has only 6 grounded pins when i tested it.

Thanks in advance for a reply!

 

[digitalplat4m]

Backlight Went Out....Again......

Hello everyone. I had previously fixed the back light on my Macbook Pro 13 (mid 2010) by replacing the 2A fuse and got it to work (many thanks to Dadioh). Since then I, inadvertently blew the fuse again when attempting to replace the airport card. I replaced the fuse (again) but the back light is still not working.

Measured across the fuse and the fuse is good.
I plugged in the battery and measured the diode (on the cathode) and got 0 volts.
I measured the 4th or 5th pin on the WLED and got 3.4 volts.
The LVDS Display cable has a couple of damaged pins (see photo). Could this be the problem or does the WLED need to be replaced or both?

Many thanks to all.
http://www.flickr.com/photos/33731170@N06/6908289717/in/photostream/lightbox/

 

[Dadioh]

Hello everyone. I had previously fixed the back light on my Macbook Pro 13 (mid 2010) by replacing the 2A fuse and got it to work (many thanks to Dadioh). Since then I, inadvertently blew the fuse again when attempting to replace the airport card. I replaced the fuse (again) but the back light is still not working.

Measured across the fuse and the fuse is good.
I plugged in the battery and measured the diode (on the cathode) and got 0 volts.
I measured the 4th or 5th pin on the WLED and got 3.4 volts.
The LVDS Display cable has a couple of damaged pins (see photo). Could this be the problem or does the WLED need to be replaced or both?

Many thanks to all.
http://www.flickr.com/photos/33731170@N06/6908289717/in/photostream/lightbox/

Image

Those are the backlight pins so you need to replace the lvds cable. That requires removing the glass on the display. Tricky job. You may also need to replace the connector on the logic board. You need to examine it under magnification.

 

[russthechamp]

I am traveling now so just a quick answer. The missing black component on the right is probably the inductor. This is the middle inductor in the PI filter in the schematic. As a quick test you could short the pads to see if that restores wifi function. Best to replace it if you can since electromagnetic emissions would be higher without the filter. Do you have access to a spare parts board?

I shorted the connections on the fried inductor, and still no wifi Do you know if there is a fuse for the power line that supplies the voltage to the wifi card? Or perhaps any other thoughts or suggestions?

Thanks
Russ

 

[Dadioh]

I shorted the connections on the fried inductor, and still no wifi Do you know if there is a fuse for the power line that supplies the voltage to the wifi card? Or perhaps any other thoughts or suggestions?

Thanks
Russ

Do you have 3.3v appearing at the inductor you shorted? We are trying to get 3.3v power to the connector pins. I would have to check the schematic but I don't remember there being a fuse. That would explain why the inductor vaporized. A fuse would have prevented that.