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Old Mar 15, 2011, 07:00 PM   #101
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Originally Posted by alancookie View Post
I think I may have this same issue with a MBP17 (A1212). Any advice or photos of where this fuse may be on the motherboard? I removed my screen assembly and connected it to a same model MBP17 and the backlight worked...so I'm pretty sure I have eliminated the inverter, inverter cable and backlight itself.
That's a 2006 Model? If so it is an LCD screen with CCFL backlight. All of the discussion here is about the LED backlit screens where the LEDs are driven by a circuit that generates 27V DC. The LCD screens use an inverter board that generates significantly higher voltage for the fluorescent tube. Completely different technology I'm afraid
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Old Mar 16, 2011, 10:37 AM   #102
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Thank you everyone for their info on here - it has been very helpful!!

Dadioh did you buy the LP8543 WLED driver direct from National? I need to order a few of these here in the UK and wondered if there was anyone that stocked these locally? have previously removed these off logic boards that have been beyond repair but feel this is not the best way as often they are faulty and the heat used to remove them can't do them any good..

I have quite a few unibody logic boards suffering liquid damage with back light issues but a couple with other power issues and wondered if anyone else had this following fault? The logic boards will not power up with battery connected but if you unplug battery and do and SMC reset start (disconnect magsafe, hold power button down for 10 seconds, connect magsafe while holding power button for another 10 secs, release power button and then press power button again and logic board powers up) the fan will run on high but everything works fine. Does anyone know what component might be causing this problem and preventing start up normally? I have about 5 logic boards with this problem now and cannot figure it out!
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Old Mar 16, 2011, 03:48 PM   #103
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Thank you everyone for their info on here - it has been very helpful!!

Dadioh did you buy the LP8543 WLED driver direct from National? I need to order a few of these here in the UK and wondered if there was anyone that stocked these locally? have previously removed these off logic boards that have been beyond repair but feel this is not the best way as often they are faulty and the heat used to remove them can't do them any good..

I have quite a few unibody logic boards suffering liquid damage with back light issues but a couple with other power issues and wondered if anyone else had this following fault? The logic boards will not power up with battery connected but if you unplug battery and do and SMC reset start (disconnect magsafe, hold power button down for 10 seconds, connect magsafe while holding power button for another 10 secs, release power button and then press power button again and logic board powers up) the fan will run on high but everything works fine. Does anyone know what component might be causing this problem and preventing start up normally? I have about 5 logic boards with this problem now and cannot figure it out!
I bought mine from either Digikey or Newark but not sure what the choices are across the pond.

Very interesting information on the power up sequence. From what I understand of the way the logic board sequences power the SMC will monitor all supply voltages and then, if it is happy, will release the processors from reset. Sounds like your procedure may somehow override this check? Just guessing. I will have to try this on one of my "dog pile" boards...
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Old Mar 16, 2011, 06:02 PM   #104
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I bought mine from either Digikey or Newark but not sure what the choices are across the pond.

Very interesting information on the power up sequence. From what I understand of the way the logic board sequences power the SMC will monitor all supply voltages and then, if it is happy, will release the processors from reset. Sounds like your procedure may somehow override this check? Just guessing. I will have to try this on one of my "dog pile" boards...
Thanks for those details. Hopefully I can find a supplier soon or maybe someone will ship from your side..

I'm sure you will find a couple of boards that may work with this start-up sequence, and I think you are the one with the knowledge to source the faulty component! I have swapped out the Macronix MX25L3205 flashrom from another working logic board, where I believe the SMC information is stored, but this does not make any difference. So I'm sure something before the flashrom has gotta be at fault here. Would be great if someone could figure this one out!
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Old Mar 16, 2011, 10:29 PM   #105
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There should be a diode near the LVDS connector. On the cathode of that diode (marked with a white stripe) is the 27V that drives the LED's in the display. If you have approximately 27V there but no backlight then the issue is either the LVDS cable or the display. If there is no voltage then it is the WLED driver circuit. You want to be VERY careful probing on the board while it is running. One little slip and you will let the smoke out.

This is what the diode looks like on the 13" MBP unibody.
Thanks for your replies, Dadioh. I haven't had much time lately to get back into this project but I did try to find that diode with no luck. I appreciate the schematic too, but you wouldn't have one for this A1260 Macbook would you? It's laid out pretty differently. I'm also wondering if Q9806 is supposed to measure 200k on this model and not 300k since the component is marked differently? The power to the WLED driver seems to come from the Left IO board and the LVDS cable is on the main board on the other side of the laptop, so should I be looking for the diode near the power connector for the WLED driver on the Left IO board? I can upload pics too if that would help.
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Old Mar 21, 2011, 09:18 PM   #106
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Thanks for those details. Hopefully I can find a supplier soon or maybe someone will ship from your side..

I'm sure you will find a couple of boards that may work with this start-up sequence, and I think you are the one with the knowledge to source the faulty component! I have swapped out the Macronix MX25L3205 flashrom from another working logic board, where I believe the SMC information is stored, but this does not make any difference. So I'm sure something before the flashrom has gotta be at fault here. Would be great if someone could figure this one out!
I just got a MBP off eBay that exhibits these exact same symptoms so hopefully I will be able to figure it out now that I have one in my hands. It also seems to have a bad DIMM slot because as soon as I put memory in the lower DIMM I get single beeps and no chime. But I think this is not related to this specific issue.

What I have noticed so far...

Fan runs on high speed.
iStat menus can not sense either temperature or fan speed so access to those sensors is not there. Probably why the fans run on high.
No voltages or power displayed by iStat
Can not see the battery even though it is plugged in.
Does not charge the battery.
Airport works
USB ports work
iSight Camera works
Disk/DVD both work

I think that maybe I should start another thread on this issue and not hijack this backlight thread.
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Old Mar 21, 2011, 09:41 PM   #107
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Thanks for those details. Hopefully I can find a supplier soon or maybe someone will ship from your side..

I'm sure you will find a couple of boards that may work with this start-up sequence, and I think you are the one with the knowledge to source the faulty component! I have swapped out the Macronix MX25L3205 flashrom from another working logic board, where I believe the SMC information is stored, but this does not make any difference. So I'm sure something before the flashrom has gotta be at fault here. Would be great if someone could figure this one out!
For those with an interest in this particular SMC related fault I am moving that discussion off to a different thread so that we do not derail the LED Backlight discussions in this thread. See link below.

http://forums.macrumors.com/showthre...7#post12219797
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Old Mar 30, 2011, 05:44 AM   #108
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I've read through this thread and it seems like a lot of people are having success. I'm hoping that I'll get lucky too.

I have a 15" Unibody macbook pro, mid 2009. I spilt water on it and like most people here, everything works except the backlight for the LCD.

I've taken it apart and I'm trying to find the fuse in question but I'm having no luck. I'm thinking it might be on the other side of the board (like in the case of the person with the 17" macbook) but want to avoid taking it apart to that level if it's just a case of me being a blind wombat.

Dadioh, it seems like you've become the man to go to when it comes to this problem. There are two pictures of the logic board (front and back) along with zoom options on http://www.ifixit.com/MacBook-Parts/...oard/IF161-028

Would you kindly take a look and tell me if you can spot the fuse on either the top or underneath of the board based on those pics?

Thanks a lot.
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Old Mar 30, 2011, 06:23 AM   #109
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I carefully followed the steps on Ifixit.com and managed to remove the logic board. I think I've found the fuse on the underside of the board.

<pics removed>
I removed the pics because I'd got it completely wrong. I've now managed to find it by looking at cherokeejerods pics. God that thing is so small. Even with a magnifying glass I can barely see it!

Also, here's a picture of the LCD cable. I'm guessing it shouldn't look like that and that and perhaps a couple of those pins are damaged? Could that be causing the backlight not to work?


Last edited by philstuffs; Mar 30, 2011 at 06:56 AM.
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Old Mar 30, 2011, 07:38 AM   #110
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It seems that the backlight isn't related to the display cable, so i guess my cable is working okay.

I'm going to have to take the board to the mall tomorrow (lots of cell/laptop repair shops) and ask them to check the fuse. I can't reliably test it because it's so small, I keep touching other parts.

I'll write down notes from this thread and ask them to test it for me and replace it if it is indeed damaged. I don't know if this is a fuse that they'd generally stock. Perhaps If the fuse is broken and they don't have a replacement fuse, I'll ask them to use a blob of solder so we can at least test if that is indeed the problem.

I'll come back with an update tomorrow.

Cheers
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Old Mar 30, 2011, 07:45 AM   #111
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I carefully followed the steps on Ifixit.com and managed to remove the logic board. I think I've found the fuse on the underside of the board.

<pics removed>
I removed the pics because I'd got it completely wrong. I've now managed to find it by looking at cherokeejerods pics. God that thing is so small. Even with a magnifying glass I can barely see it!

Also, here's a picture of the LCD cable. I'm guessing it shouldn't look like that and that and perhaps a couple of those pins are damaged? Could that be causing the backlight not to work?

Yeah. VERY tiny. That is called an 0402 package (0.04" 0.02"). You will need a stereo microscope and a very fine tip soldering iron to do it right. Or a set of eagle eyes I suppose.

If the pinout on that LVDS cable is the same as on the 13" then those pins are either the 3.3V power to the LCD display logic OR the LCD Backlight voltage (can't remember which end of the cable is pin 1). Pin 1 would be ground so you could ohm out the connector on the board and find out which end is which.

pin 1 = gnd
pin 2 = PP3V3 SW LCD
pin 3 = PP3V3 SW LCD
....
pin 28 = PPVOUT_S0_LCDBKLT
pin 29 = PPVOUT_S0_LCDBKLT
pin 30 = PPVOUT_S0_LCDBKLT


edit: just noticed your cable is 40 pins rather than the 30 pins used on 13" display. However, I think that the far ends of the connector still match up. So it would be pins 38, 39, 40 for you rather than pins 28, 29, 30 for the 13".

They don't look good though. You may be looking at replacing the cable which is a real chore given the glass panel over the display. I tried on 2 different displays to get that off (using iFixit technique with suction cup) and broke both of them. You may be better at it than me.
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Old Mar 30, 2011, 11:13 AM   #112
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Dadioh, I admire your dedication to helping people with this problem. Thanks for replying!

I'm seeing a picture on the screen, just no backlight. Could the backlight problem be related to the LVDS cable? You said that some of the pins are used for backlight voltage. Is it likely that those 2 damaged pins are the ones that control it and therefore the likely cause of the backlight not working?

If it's likely to be a problem with the cable then it might not be worth me trudging across town tomorrow morning to have them check the fuse.

A local computer shop got a quote from Apple for a new screen and it came in at $850. At that price I might as well just scrap it and buy a new laptop!

I'm not great at things like this so if you couldn't manage it then there's very little hope for me!

Cheers
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Old Mar 30, 2011, 12:24 PM   #113
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Dadioh, I admire your dedication to helping people with this problem. Thanks for replying!

I'm seeing a picture on the screen, just no backlight. Could the backlight problem be related to the LVDS cable? You said that some of the pins are used for backlight voltage. Is it likely that those 2 damaged pins are the ones that control it and therefore the likely cause of the backlight not working?

If it's likely to be a problem with the cable then it might not be worth me trudging across town tomorrow morning to have them check the fuse.

A local computer shop got a quote from Apple for a new screen and it came in at $850. At that price I might as well just scrap it and buy a new laptop!

I'm not great at things like this so if you couldn't manage it then there's very little hope for me!

Cheers
No problem. Glad to help. I would say those pins are definitely part of the problem. The LVDS cable carries the backlight voltage. I suspect that those pins are the Backlight voltage that lights the LEDS. Runs at about 27V when the display is on max brightness.

Given the look of them it is quite possible that there could be other parts of the drive circuit that could have an issue, If you are lucky it is only the fuse that is blown. It is also possible to blow the WLED driver chip.

I suspect you don't have access to a multimeter to check the fuse? It would be a shame if you got a replacement LCD display and there was other stuff to fix. If you take it to a shop get them to measure that fuse before they do anything else.

You may be able to find a used screen on eBay and save some money.
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Old Mar 31, 2011, 01:22 AM   #114
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Well I did go out and buy a multimeter, but with the fuse being so small, I'm finding it hard to ensure I'm only touching either side of the fuse and not surrounding parts.

My fear is that even if the fuse is blown, the cable would also need to be replaced if those damaged pins are used to carry voltage over to the LED backlight.
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Old Mar 31, 2011, 08:41 AM   #115
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Well I did go out and buy a multimeter, but with the fuse being so small, I'm finding it hard to ensure I'm only touching either side of the fuse and not surrounding parts.

My fear is that even if the fuse is blown, the cable would also need to be replaced if those damaged pins are used to carry voltage over to the LED backlight.

These are the probes that I use with my multimeter.

http://www.newark.com/pomona/6342/te...58?Ntt=91B0558

Regular probe tips are too big to get reliable connection to small devices.

Yes. I think that the cable needs to be replaced. It is not a trivial job however given the way the displays are built. You need to remove the glass cover and this is VERY difficult to do from my experience. Some claim it is easy but I am 0 for 2 in this department.

If you are not wanting to risk it I would just sell your display assembly on eBay with the known cable defect. Someone somewhere will probably buy it to fix it. Then buy yourself a used display assembly with a guarantee.

Or you could sell the whole laptop as-is and get yourself a replacement. The difference for what you can sell it for and what you can buy a used one for may be less hassle than the repair.

Tough choices....
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Old Mar 31, 2011, 08:51 AM   #116
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Dadioh, thanks again for the advice. To be honest, I think I'll just keep it as a local web server. That's what I originally used it for when it first broke.

It was only when my girlfriends laptop started failing that I hoped I could fix my macbook pro and give it to her.

I'm currently in a "third world" country, so selling online would be difficult with the high shipping prices, since anyone interested would probably be in the US/UK.

Funnily enough, If I shine a 40 watt spotlight at the apple logo, I can light up pretty much the whole screen. It's a shame that the display is such a nightmare to take apart otherwise I could imagine simply hardwiring the LED backlight to a power source in the laptop. Okay you'd loose brightness controls, but still..!
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Old Mar 31, 2011, 09:44 AM   #117
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Dadioh, thanks again for the advice. To be honest, I think I'll just keep it as a local web server. That's what I originally used it for when it first broke.

It was only when my girlfriends laptop started failing that I hoped I could fix my macbook pro and give it to her.

I'm currently in a "third world" country, so selling online would be difficult with the high shipping prices, since anyone interested would probably be in the US/UK.

Funnily enough, If I shine a 40 watt spotlight at the apple logo, I can light up pretty much the whole screen. It's a shame that the display is such a nightmare to take apart otherwise I could imagine simply hardwiring the LED backlight to a power source in the laptop. Okay you'd loose brightness controls, but still..!
Good call. I have a Macbook Pro 13 unibody that had a failed backlight that I could not fix. So I removed the display to make a nice headless unit and mounted it under my plasma screen. It now runs Plex as a media server and looks just beautiful with that lighted keyboard and aluminum goodness. And I use a magic trackpad and Apple wireless keyboard tied together with a "magic wand" for that "sit back on the couch and use a 50 inch screen to surf the web" experience Get's lots of comments by visitors
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Old Apr 4, 2011, 12:38 PM   #118
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I am having the same problem with the macbook now. The backlight was flickering due to WD so I cleaned the lcd connectors area with alcohol and it was still flickering but after a few minutes it finally died out. LCD still works but it's very dim. so I think the L8543sq IC is fried. I *think* it has a burn spot were the q is on the IC so I'll have to replace that. Any ideas where I can get the IC?
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Old Apr 4, 2011, 12:45 PM   #119
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I am having the same problem with the macbook now. The backlight was flickering due to WD so I cleaned the lcd connectors area with alcohol and it was still flickering but after a few minutes it finally died out. LCD still works but it's very dim. so I think the L8543sq IC is fried. I *think* it has a burn spot were the q is on the IC so I'll have to replace that. Any ideas where I can get the IC?
Check the fuse first before you assume it is the driver device.

You can get the driver at Digikey. Linked below.

http://search.digikey.com/scripts/Dk...43SQ/NOPBCT-ND
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Old Apr 4, 2011, 01:07 PM   #120
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Check the fuse first before you assume it is the driver device.

You can get the driver at Digikey. Linked below.

http://search.digikey.com/scripts/Dk...43SQ/NOPBCT-ND
well the reason why I'm pretty positive it is the driver it's because I bypassed the fuse to test it by connecting a wire from one end to the other. Same result. I took the IC out and there was a corner that was rusted ish so I put some flux and some new led on it and it looks as good as new but the driver has a little hole on it as if it was burnt so I'm under the impression that if I replace that it will be as good as new.
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Old Apr 4, 2011, 01:29 PM   #121
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well the reason why I'm pretty positive it is the driver it's because I bypassed the fuse to test it by connecting a wire from one end to the other. Same result. I took the IC out and there was a corner that was rusted ish so I put some flux and some new led on it and it looks as good as new but the driver has a little hole on it as if it was burnt so I'm under the impression that if I replace that it will be as good as new.
Ok. Makes sense. Also a fuse would not fail intermittently as you have described. A new WLED chip should fix you up. Since you have already removed and replaced once you know your way around soldering. Good luck with the replacement. Let us know how it goes.
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Old Apr 4, 2011, 04:24 PM   #122
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I went ahead and ordered the one from diji-key you supplied a link to. Shipping Method: FedEx International Priority we'll see how that goes hopefully it'll be here tomorrow or the day after
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Old Apr 6, 2011, 03:51 PM   #123
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Red face

went ahead and replaced the driver.

Success!!

thanks Dadioh
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Old Apr 6, 2011, 06:01 PM   #124
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went ahead and replaced the driver.

Success!!

thanks Dadioh
Congrats!!!
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Old Apr 6, 2011, 09:46 PM   #125
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Congrats!!!
couldn't have done it without you.
on a side note I must mention:
after replacement of the driver and reassembly of the computer I had no display. turns out I needed to reset the computer by:
1) have the computer shut off and then press and hold the power button. (this did it for me) but I chose to reset the pram as well
2) right after turning on press and hold comman+option+P+R until you hear it restart again.
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