MacBook Pro Unibody - No Backlight - Logic Board Question

[Dadioh]

Started a thread to be used just for locating the fuses on various boards. I added the MBP13" 2009 model to start. Will add more as I get the time to document them.

https://forums.macrumors.com/showthread.php?p=17815694#post17815694

 

[Astroboy907]

Started a thread to be used just for locating the fuses on various boards. I added the MBP13" 2009 model to start. Will add more as I get the time to document them.

https://forums.macrumors.com/showthread.php?p=17815694#post17815694

Count me for an A1278 Mid 2010, will get pics to you today.

Edit: maybe the inclusion of the WLED driver and backlight pins on the LDVS would be helpful? Maybe a but too far?

 

[Astroboy907]

Well I tested what I could of the WLED and none of the pins were shorted to ground (aside from those that should've been), so I replaced the fuse, and tried to solder up the connections on the LVDS. The fuse doesn't blow again, but the backlight won't turn back on. Pins 22 and 24 I think of the WLED (pic in my post a couple back), look like the contacts are blown maybe? Still no backlight... Any ideas? I might have taken off one of the fuse pads on the board but it soldered back on seemingly without any problems... Backlight voltage is 11 some volts.

Oh, and sorry about not getting pics to you but I wanted to double check where the fuse was...

 

[midijamm]

Riddle me this?

Hi all, I'm new to forum, lots of good info here! Waiting for response from thxkbye on his board's readings. I have a 15" mac pro unibody mid 2010 i5 board(820-2850-A)


Hey Nerds, (I am assuming no one here will be offended by that)
I have been looking through all 57 or so pages here to find my mid 2009 15" MBP mobo backlight fuse location and came upon the above post and below pic. It says it is a 2010 i5. It is just like my mid 2009 (not i5) I guess they used the same layout with a different processor?

Any way, My fuse appears to be blown and I get 300=/- k ohms from the indicated legs of 638Z but I get 7.45 M ohms to 11. 5 M ohms across the fuse and weird intermittent readings from one end of the fuse to ground!

The usual reading I get (fuse to ground) is a descending number of M ohms starting anywhere from 30 M ohms downward and then continuous descending readings in small graduations and eventually settling at 2.09 M ohms or 1.88 or some other random small number. It seems to read consistently 1. something M ohms once it settles down to a low #

Whatitis??????

Cheapo UEI meter??

Are these acceptable numbers?

 

[Dadioh]

Hi all, I'm new to forum, lots of good info here! Waiting for response from thxkbye on his board's readings. I have a 15" mac pro unibody mid 2010 i5 board(820-2850-A)


Hey Nerds, (I am assuming no one here will be offended by that)
I have been looking through all 57 or so pages here to find my mid 2009 15" MBP mobo backlight fuse location and came upon the above post and below pic. It says it is a 2010 i5. It is just like my mid 2009 (not i5) I guess they used the same layout with a different processor?

Any way, My fuse appears to be blown and I get 300=/- k ohms from the indicated legs of 638Z but I get 7.45 M ohms to 11. 5 M ohms across the fuse and weird intermittent readings from one end of the fuse to ground!

The usual reading I get (fuse to ground) is a descending number of M ohms starting anywhere from 30 M ohms downward and then continuous descending readings in small graduations and eventually settling at 2.09 M ohms or 1.88 or some other random small number. It seems to read consistently 1. something M ohms once it settles down to a low #

Whatitis??????

Cheapo UEI meter??

Are these acceptable numbers?

Ascending or descending readings in megaohms is a side effect of how meters read resistance. They apply a small voltage and read how much current flows. They then calculate resitance. This is why you can only measure resistance with a meter on a powered off board. In your case this applied voltage from the meter is charging or discharging a capacitor somewhere and thus the claculated resistance changes as that cap charges or discharges. No need to worry about it.

The main thing you need to worry about is the resistance across the fuse. If it is good then you measure a couple of ohms (depending on how good your meter and test leads are). If you are measuring kohms or Mohms then the fuse is blown

 

[Snappaz]

I also have a liquid damaged Macbook pro.

The battery is not working and the backlight is not working.

One thing that I noticed that could be the problem with the battery is this part (I didn't test another battery and I also did not connect the macbook on external screen yet):

I'm getting this amount of Ohms when i measure the resistance off the backlight fuse:

This is the right fuse, right ?

The WLED Driver and Display connector seemed okay to me.

This is a MBP Mid 2010 2.4Ghz/320M Nvidia

 

[Astroboy907]

This is the right fuse, right ?
Image

The WLED Driver and Display connector seemed okay to me.

This is a MBP Mid 2010 2.4Ghz/320M Nvidia

If it is the 13" I think it is. I replaced mine (which didn't work, but I hope it is a different problem, and not a wrong fuse location).
See this pic, I think it is the same board.

As for my own 13", the stupid pin on the LVDS cable broke off. Guess I need a new connector I'm pretty screwed.
Edit: got rid of the computer. Saving up for some decent tools

 

[Snappaz]

What about the first picture?

Something is also wrong with that part I assume.

Here's another picture of the part:

 

[Dadioh]

What about the first picture?

Something is also wrong with that part I assume.

Here's another picture of the part:

Image

That capacitor looks like it has been physically hit. Should reflow the solder and straighten it if the body of the cap is undamaged.

It is C6990 and it is the filter cap on the input of the circuit that generates G3Hot 3.4V. See attachments. Are you getting 3.4V on G3Hot?

Also, for those reading this, here are the steps you follow when you see a component that you are wondering about....

1) Open the boardview file and identify the component of interest. Clicking on one of the leads will tell you the signal name and part id.
2) Search for the part on the schematic. You can use the component id or the signal net name.
3) Figure out what the component does. This will require some electronic knowledge.

 

[Astroboy907]

That capacitor looks like it has been physically hit. Should reflow the solder and straighten it if the body of the cap is undamaged.

It is C6990 and it is the filter cap on the input of the circuit that generates G3Hot 3.4V. See attachments. Are you getting 3.4V on G3Hot?

Also, for those reading this, here are the steps you follow when you see a component that you are wondering about....

1) Open the boardview file and identify the component of interest. Clicking on one of the leads will tell you the signal name and part id.
2) Search for the part on the schematic. You can use the component id or the signal net name.
3) Figure out what the component does. This will require some electronic knowledge.

Don't want to hijack but I have a question. Recently I won a lot of macbook screens off of eBay. I got them today and put one on my Mac, and it works awesome. I did notice the LVDS got a bit hot though, but thought nothing to it. Put another screen on to test, and my backlight dies. Of course, it's the fuse so I replace that and put the first screen on. Backlight comes on, but within a few seconds the LVDS is burning and I see smoke. Pulled the battery. And of course, I put the second screen back on and it blows my fuse again- kind of. It's now reading approx 1.35k. No backlight on the original screen... Don't know if its the WLED or not...

I have another couple fuses but I don't want to solder another if its going to break again... Plus the fuse doesn't seem to be burnt. Really confused and screwed at this point because this is my daily machine will be out of town for a couple days but I would like this to be working in two weeks if possible.

 

[thebe]

Hello, my APP001A WLED Driver is blowen up. Now i am looking since 3 hours for a new one but i cant find it. Have someone a idea?

thx thebe

 

[nemo.]

Hi all,

I've replaced the WLED driver on my k90i and suddenly there are
24V at caps before the display cable (12V before driver replacement).
However, I'm still not getting backlight.

Any ideas why this is the case?

Thanks!

...

 

[Dadioh]

Hi all,

I've replaced the WLED driver on my k90i and suddenly there are
24V at caps before the display cable (12V before driver replacement).
However, I'm still not getting backlight.

Any ideas why this is the case?

Thanks!

Bad lvds cable
Bad lvds connector
Bad LEDs in display

Can you try a known good display?

----------

Hello, my APP001A WLED Driver is blowen up. Now i am looking since 3 hours for a new one but i cant find it. Have someone a idea?

thx thebe

As far as I know the APP001 is not publicly available. You would need to salvage one off a spare parts board.

 

[nemo.]

Bad lvds cable
Bad lvds connector
Bad LEDs in display

Can you try a known good display?

Sadly I have no spare parts, so no.

I assume that there's no way to test the cable
without opening the display? I will try to measure
the pins inside the connector to verify that the
connector is OK.

Is there a guide somewhere how to open the display
without damaging it?

Thanks.

 

[Dadioh]

Sadly I have no spare parts, so no.

I assume that there's no way to test the cable
without opening the display? I will try to measure
the pins inside the connector to verify that the
connector is OK.

Is there a guide somewhere how to open the display
without damaging it?

Thanks.

You could try unplugging the lvds connector and then measuring the resistance between the backlight pins and the cable shield. You should be seeing the resistance of the led strings. Not sure what that should be and I am not home to test it. Maybe someone else can measure and report.

 

[nemo.]

You could try unplugging the lvds connector and then measuring the resistance between the backlight pins and the cable shield. You should be seeing the resistance of the led strings. Not sure what that should be and I am not home to test it. Maybe someone else can measure and report.

LED_RETURN 6-1 as well as PPVOUT_SW_LCDBKLT have 'infinite' resistance
(measuring up to 2MOhm). I measured from the hinge of the connector
to said pins (GND connectors are reporting 0 Ohm resistance so the hinge
is indeed a mass).

I get a video signal so if the cable is damaged it is only for these wires.

 

[Dadioh]

LED_RETURN 6-1 as well as PPVOUT_SW_LCDBKLT have 'infinite' resistance
(measuring up to 2MOhm). I measured from the hinge of the connector
to said pins (GND connectors are reporting 0 Ohm resistance so the hinge
is indeed a mass).

I get a video signal so if the cable is damaged it is only for these wires.

Actually, thinking about it now, the return signals are isolated from ground so what you want is to measure the led strings. So you would want one lead on the backlight pin and the other lead on one of the returns. Since the LEDs are diodes you would get different readings if you reverse the leads. Some meters have a diode measurement setting. You could use that as well.



The returns would be isolated from ground so you expect a high resistance to ground.

 

[nemo.]

Actually, thinking about it now, the return signals are isolated from ground so what you want is to measure the led strings. So you would want one lead on the backlight pin and the other lead on one of the returns. Since the LEDs are diodes you would get different readings if you reverse the leads. Some meters have a diode measurement setting. You could use that as well.



The returns would be isolated from ground so you expect a high resistance to ground.

I used the diode measurement setting on my meter and it was always high, so no diode in reach. Measured from every return to every backlight pin.
I also swapped the probes but no difference.

 

[Dadioh]

I used the diode measurement setting on my meter and it was always high, so no diode in reach. Measured from every return to every backlight pin.
I also swapped the probes but no difference.

Hmmm. Well that sounds like the led strings are open circuit. Could be the lvds cable or the display panel. Would be advisable to get another display assembly to try.

 

[nemo.]

Hmmm. Well that sounds like the led strings are open circuit. Could be the lvds cable or the display panel. Would be advisable to get another display assembly to try.

As I said, I have no spare parts so a different display assembly is going
to be difficult to find. I could ask at my local mac repair shop although I don't
think that they have one there.

I guess repairing the display is out of question?

 

[Dadioh]

As I said, I have no spare parts so a different display assembly is going
to be difficult to find. I could ask at my local mac repair shop although I don't
think that they have one there.

I guess repairing the display is out of question?

Well you would need to start with removing the glass. Tricky job. Then you would be able to troubleshoot if it is the LCD panel or the cable. But before taking the glass off (risk of breakage) it would be nice to be 100% certain it is not the logic board. Your experiments suggest that it is the display but I am trying to proceed with caution.

Spare parts to use in diagnostics is pretty important to me so I keep spares of just about everything. But that is not possible for everyone especially those who are doing a fix on their own single machine.

 

[nemo.]

Well you would need to start with removing the glass. Tricky job. Then you would be able to troubleshoot if it is the LCD panel or the cable. But before taking the glass off (risk of breakage) it would be nice to be 100% certain it is not the logic board. Your experiments suggest that it is the display but I am trying to proceed with caution.

Spare parts to use in diagnostics is pretty important to me so I keep spares of just about everything. But that is not possible for everyone especially those who are doing a fix on their own single machine.

Alright, thanks. I'll try my luck with my local mac repair shop and report back.

Update:

You were right with waiting to open the display. The backlight works now.
If I recall correctly, the only thing I was doing is leaving the battery unplugged
for some time and reconnecting the LVDS cable. I also did some scratching
on the LVDS connectors when doing the measurements. It may just have been
dirty (the MacBook was full of energy drink, so...) and therefore missing connectivity.

Anyway, everything seems to work now. One more MacBook repaired due to
this and the SMC thread

 

[mazzano4]

macbook pro 2008 backlight issue

Hi, i wonder if you can help, im not sure if im having this issue but ive read through nearly every page of this most informative thread.

i have a macbook pro late 2008 17 inch. I think, anyway the back light is failing intermittently, sometimes it will work but then it will go off and sometimes will come back on, but sometimes works when rebooted but then sometimes won't, i am actually on it now, and the backlight has managed to stay on for an hour this time, The gpu just got a reflow today,could this be anything to do with it. or is it cables or this fuse, could you tell me where this fuse is on my machine, thats why i read the other posts, to see if i could find it but i couldn't .

Please let me know. Because it might not come back on again haha, ps you can see the desktop when the light goes off, also, there was no liquid split on this.

Thanks

 

[Dadioh]

Hi, i wonder if you can help, im not sure if im having this issue but ive read through nearly every page of this most informative thread.

i have a macbook pro late 2008 17 inch. I think, anyway the back light is failing intermittently, sometimes it will work but then it will go off and sometimes will come back on, but sometimes works when rebooted but then sometimes won't, i am actually on it now, and the backlight has managed to stay on for an hour this time, The gpu just got a reflow today,could this be anything to do with it. or is it cables or this fuse, could you tell me where this fuse is on my machine, thats why i read the other posts, to see if i could find it but i couldn't .

Please let me know. Because it might not come back on again haha, ps you can see the desktop when the light goes off, also, there was no liquid split on this.

Thanks

If it is this model then it is a CCFL backlight and not an LED backlight. The CCFL is a fluorescent tube and requires an inverter to generate a high voltage for the tube so it is possible that you have a bad inverter or the cable could be bad. But I have never worked on that model so I can't help with locating the inverter.

 

[midijamm]

If it is this model then it is a CCFL backlight and not an LED backlight. The CCFL is a fluorescent tube and requires an inverter to generate a high voltage for the tube so it is possible that you have a bad inverter or the cable could be bad. But I have never worked on that model so I can't help with locating the inverter.

The inverter is in the base of the display

Really not too hard to get to. Ifixit shows you how

http://www.ifixit.com/Guide/Replaci...A1212+A1229+and+A1261+Display+Inverter/2626/1