MacBook Pro Unibody - No Backlight - Logic Board Question

[thortuletz]

Thank you, but i already got.... Thanks Anyway for taking the time

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Have you checked underneath the wled chip for corrosion? You may need to reball or replace it...
Also check the inductor, capacitor nearby.. Is it clean??
The LCD connector pins on the board is clean?

under the wled i didn't check but today i clean the board again, same problem nothing changed connector is clean no problem there i didn't mention that the second time when i spilled water i didn't have the fuse, was just soldered
correct me if i'm wrong the wled driver on my board is VM16AB right? any other ideas? all capacitor they are clean no corrosion lvds conector clean wled clean. what should i do?

 

[emin94h]

sorry my bad, that was bigfoot. Well the schematics should help some..

Check the stuff that comes after F9700, the q9706, q9707, R9715

What should I look after there?

 

[cpufixer]

What should I look after there?

check schematics, these are fet's, youtube will show how to check, should not be shorted.
Also, your board looks clean, can you find any discolored white probe points?

 

[emin94h]

check schematics, these are fet's, youtube will show how to check, should not be shorted.
Also, your board looks clean, can you find any discolored white probe points?

I managed to open the board viewer and opened up my board, didn't know what you where talking about when you posted it before.
The voltage divider could be the problem, R9731 & R9715 also C9799 which is where the backlight output ends. Should I check these, diode mode?

 

[cpufixer]

I managed to open the board viewer and opened up my board, didn't know what you where talking about when you posted it before.
The voltage divider could be the problem, R9731 & R9715 also C9799 which is where the backlight output ends. Should I check these, diode mode?

should get 100 k ohm's at r9715, nothing should be shorted to ground at the cap's, look for discoloration on parts or board, that will give some hints.

 

[emin94h]

should get 100 k ohm's at r9715, nothing should be shorted to ground at the cap's, look for discoloration on parts or board, that will give some hints.

I don't see any discoloration on the parts. Did some testing before, here is what I got:

C9797 - reads 002 and beeps in diode mode (to ground). I'm getting 00.3 (200ohm) when measuring resistance to ground, 673 (2000ohm) when measuring resistance across the cap and a readout of 731 in diode mode across the cap (doesn't beep).

C9799 - Same here, 002 diode mode (beeps), 00.3 (200ohm) resistance to ground, 673 (2000ohm) resistance across the cap and 731 across the cap in diode mode (doesn't beep).

C9796 - Same here, 002 diode mode (beeps), 00.3 (200ohm) resistance to ground, 673 (2000ohm) resistance across the cap and 731 across the cap in diode mode (doesn't beep).

D9701 - getting 213 across the cap in diode mode (doesn't beep).
482 with negative to ground and positive on PPBUS_SW_BKL.
732 with negative to ground and positive on PPBUS_SW_LCDBKLT_PWR_SW.
131,8ohm (200ohm) and 192ohm (2000ohm) when measuring resistance.

R9715 - getting 690 across the cap in diode mode (doesn't beep).
99,6ohm (200Kohm) with negative on BKL_EN and positive on GND.
25,9ohm (200Kohm) with negative on GND and positive on BKL_EN.

R9731 - 483 in diode mode with negative to ground and positive on PPBUS_SW_LCDBKLT_PWR (doesn't beep).
1090 the disappears in diode mode with positive on BKL_EN.
3,09 ohm (20Kohm) with negative to ground when measuring resistance.
19,25ohm (20Kohm) with negative on BKL_EN and positive on PPBUS_SW_LCDBKLT_PWR.
12,57ohm (20Kohm) - /vice versa
94,3ohm (200Kohm) with negative on BKL_EN and positive on PPBUS_SW_LCDBKLT_PWR.
184,2ohm (200Kohm) then disappears - /vice versa

I don't know if I did it right but I tried get every possible reading,
this is my multimeter btw: http://www.inmotion.pt/store/images/3/INM-0727.jpg
hope this was to any good.

 

[cpufixer]

I don't see any discoloration on the parts. Did some testing before, here is what I got:

C9797 - reads 002 and beeps in diode mode (to ground). I'm getting 00.3 (200ohm) when measuring resistance to ground, 673 (2000ohm) when measuring resistance across the cap and a readout of 731 in diode mode across the cap (doesn't beep).

C9799 - Same here, 002 diode mode (beeps), 00.3 (200ohm) resistance to ground, 673 (2000ohm) resistance across the cap and 731 across the cap in diode mode (doesn't beep).

C9796 - Same here, 002 diode mode (beeps), 00.3 (200ohm) resistance to ground, 673 (2000ohm) resistance across the cap and 731 across the cap in diode mode (doesn't beep).

D9701 - getting 213 across the cap in diode mode (doesn't beep).
482 with negative to ground and positive on PPBUS_SW_BKL.
732 with negative to ground and positive on PPBUS_SW_LCDBKLT_PWR_SW.
131,8ohm (200ohm) and 192ohm (2000ohm) when measuring resistance.

R9715 - getting 690 across the cap in diode mode (doesn't beep).
99,6ohm (200Kohm) with negative on BKL_EN and positive on GND.
25,9ohm (200Kohm) with negative on GND and positive on BKL_EN.

R9731 - 483 in diode mode with negative to ground and positive on PPBUS_SW_LCDBKLT_PWR (doesn't beep).
1090 the disappears in diode mode with positive on BKL_EN.
3,09 ohm (20Kohm) with negative to ground when measuring resistance.
19,25ohm (20Kohm) with negative on BKL_EN and positive on PPBUS_SW_LCDBKLT_PWR.
12,57ohm (20Kohm) - /vice versa
94,3ohm (200Kohm) with negative on BKL_EN and positive on PPBUS_SW_LCDBKLT_PWR.
184,2ohm (200Kohm) then disappears - /vice versa

I don't know if I did it right but I tried get every possible reading,
this is my multimeter btw: http://www.inmotion.pt/store/images/3/INM-0727.jpg
hope this was to any good.

watch this.
https://www.youtube.com/watch?v=885LDVit1Yw&list=UUl2mFZoRqjw_ELax4Yisf6w
https://www.youtube.com/watch?v=_zfple3jbmg&list=UUl2mFZoRqjw_ELax4Yisf6w&index=1

 

[macrepair]

I have a 2009 13" MBP A1278 and LCD display stopped working. Have checked and its not just backlight issue there is nothing displayed on screen at all even when shining a torch onto LCD. It however works perfectly on external monitor.

I have tested with new LCD and LVDS cable but still nothing on the screen. LVDS connector also looks good and backlight fuse is good.

Does anyone know if there is a common component that fails on these laptops that would stop internal LCD coming on?

Thanks for any help

 

[emin94h]

watch this.
https://www.youtube.com/watch?v=885LDVit1Yw&list=UUl2mFZoRqjw_ELax4Yisf6w
https://www.youtube.com/watch?v=_zfple3jbmg&list=UUl2mFZoRqjw_ELax4Yisf6w&index=1

I got some help from Louis so I performed a diode test on the LVDS connector (to ground) pin 40, 39 and 38 to see if there is a short to ground none of these beeped with the LVDS cable unplugged, it didn't start to beep until the 12th pin from the left or so.
While I was at it I also measured the resistance to ground, it didn't give any reading until option 200Kohm where it increased to 180 very quick then back to 1, on 20Mohm it gave a reading of 15 and slowly started to decrease.
But with the LVDS cable plugged in, it was a whole different story, in diode mode I got a beeo on all three of the pins and it also red low resistance like 002 on the 200ohm option. Maybe I have found my short to ground bruh?

 

[thortuletz]

hey guys nobody no ideea?

 

[AGTSTi7]

macbook pro mid 2010

hello, i added a link to a picture of a little component that i need identified. ive done TONS of research and everyone is saying its 3 different things

here is the link

https://forums.macrumors.com/attachment.php?attachmentid=337480&d=1335496570

the one that is labeled capacitor in the picture is the one i need some sort of part # or something so i can order it and replace it. thanks for your help! 638z makes no sense and is not defined anywhere. i even asked digikey support and they were clueless thanks again!

 

[cpufixer]

hello, i added a link to a picture of a little component that i need identified. ive done TONS of research and everyone is saying its 3 different things

here is the link

https://forums.macrumors.com/attachment.php?attachmentid=337480&d=1335496570

the one that is labeled capacitor in the picture is the one i need some sort of part # or something so i can order it and replace it. thanks for your help! 638z makes no sense and is not defined anywhere. i even asked digikey support and they were clueless thanks again!

need board number 820-? on bottom small letters..

 

[thortuletz]

under the wled i didn't check but today i clean the board again, same problem nothing changed connector is clean no problem there i didn't mention that the second time when i spilled water i didn't have the fuse, was just soldered
correct me if i'm wrong the wled driver on my board is VM16AB right? any other ideas? all capacitor they are clean no corrosion lvds conector clean wled clean. what should i do?

ok guys i just discover something else, when the battery is full or charging ii can reach 4 dots of brightness sometime even 5, if i have less then 50-40% battery i go till 3 dots on slider maximum...
it could be a capacitor? i want to check them but i don't know what are the normal values do u know them?

if i post some pictures with the board can u locate the capacitor or if i have something called step transformer ?

 

[cpufixer]

ok guys i just discover something else, when the battery is full or charging ii can reach 4 dots of brightness sometime even 5, if i have less then 50-40% battery i go till 3 dots on slider maximum...
it could be a capacitor? i want to check them but i don't know what are the normal values do u know them?

if i post some pictures with the board can u locate the capacitor or if i have something called step transformer ?

lets try a pic ...

 

[thortuletz]

here are the pics and where is the wled? is preston ps8301 or vm16AB?

 

[cpufixer]

here are the pics and where is the wled? is preston ps8301 or vm16AB?

board number 820-2914-B, wled driver is lp8545 u9701. pin 2 is PWM for led. follow pin 2 and check resisters. Correct me if I'm wrong...

 

[maccrs]

Hi,

So I have a macbook AIR 2012 with a blown fuse and I was wondering if it would be the same fuse specified in an earlier post? (3A size 603)

The fuse is identified here but I can take a photo of my actual board if it will help?

https://forums.macrumors.com/attachment.php?attachmentid=489870&d=1410367683

ebay link: http://www.ebay.com/itm/10-Pcs-Litt...217?pt=LH_DefaultDomain_0&hash=item2a2544c4a9

Thanks so much guys!!

 

[emin94h]

watch this.
https://www.youtube.com/watch?v=885LDVit1Yw&list=UUl2mFZoRqjw_ELax4Yisf6w
https://www.youtube.com/watch?v=_zfple3jbmg&list=UUl2mFZoRqjw_ELax4Yisf6w&index=1

WTF, I mean WOW!
First off let me give you a background story. I went by the repair store the other day to see if the dude who's been repairing computers for the last 20years could help me. Left my MBP there, he said that it would be able to fix. After a week or so I went by the store to pick it up getting the message "your computer can't be fixed, your logic board is broken therefore it's not possible to fix it you have to replace it with a new one". So I took my MBP and went straight home.

I was so eager that I felt I need to open it again to do some measurements with my multimeter, btw. the MacBook still works exactly like before I went to the store. Now I see that he has removed the previous 0603 fuse I replaced, why? It was at this moment I tried some experiments on my own, so I unplugged everything from the logic board and connected the charger to do some voltage testning (have never done this before) to see if I get something like other people mentioned here. Put the the scale to the lowest which was 20 and immediately saw that pin 1 on the fuse measured 12,6volts and the other measurent something like 4,35 and started slowly to decrease. I thought why not try solder back another fuse and then see what we get. Soldered the new fuse, connected the charger like before, started measuring and tada I now have 12,60volts on pin 1 and pin 2 of the fuse and whats most exciting is that it is now reading low resistance instead of Mega ohms like the first one that blew.

I now started to understand the schematics and realized that pin 2 carries that 12,6volts further into the circuit, check the underside of the board almost everything measured 12,6 volts (C9797 & C9799) and the boost diode D9701 on both sides and even the Q9706 measured 12,6volts on every pin to ground. It also measured 300 K ohm between the lower pins (pin3 & pin4) like I saw earlier in this thread, it's the part that has 638Z4 written on it. The LVDS connector (pin 38, 39 & 40) also measured 12,56volts (unplugged) meaning that the proper voltage was getting to these components. The Q9707 measured for some reason measured 0v except from pin 3 which measured 12,07volts and pin 2 measured 3,37volts. The most weird thing is that I measured 12,58volts on pin 1 of R9731 and 3,12volts on pin 2, amazing I thought until like 2-3min from when I connected the board it now measured 0,29volts pin2 and 0,04volts pin1, how is this possible?

Does this mean that this voltage divider, together with R9715 is NOT giving the WLED driver the right amount of voltage for it to turn on or is maybe something else? Sincerely hope you or someone else could help me confirm this. Thanks.

 

[cpufixer]

EMIN, POS on Ground, NEG on fuse, you should get .581 volts in diode mode on the WLED fuse. With power removed.
just like Louis.

 

[gratabb]

Hi all, awesome thread, i've learnt masses of info so thanks to everyone involved especially Dadioh

I have a mac pro 15" A1286 820-2523 and a 17" A1297 820-2610-A, both have no backlight but can use external monitor. I have spent lots of time testing using the info from this thread and schematics.
What i have found is that on both laptops after changing the blown F9800 fuse, I have no voltage on LCD_BKLT_EN to the gate on Q9807, so no voltage out of pin 3 on Q9807 to the resistor R9809 and on to the mosfet Q9806. Pin 3 on Q9806 has the same voltage as the F9800 and nothing out the Q9806 drains.
This is the same on both laptops.
Does anyone have any ideas why?
What i was wondering was what test conditions Dadioh and others use e.g. I have just the logic board on the table with the power lead plugged in for some tests and power up the board for other tests with fans connected so i can tell its running.
I dont have the lvds cable connected usually but have tried once but it didnt seem to make any difference.
I was thinking maybe LCD_BKLT_EN isnt getting any voltage because i havent satisfied the neccessary requirements for the GPU's to enable the backlight and send the voltage to turn it on? Any ideas anyone ?

Thanks

 

[cpufixer]

Hi all, awesome thread, i've learnt masses of info so thanks to everyone involved especially Dadioh

I have a mac pro 15" A1286 820-2523 and a 17" A1297 820-2610-A, both have no backlight but can use external monitor. I have spent lots of time testing using the info from this thread and schematics.
What i have found is that on both laptops after changing the blown F9800 fuse, I have no voltage on LCD_BKLT_EN to the gate on Q9807, so no voltage out of pin 3 on Q9807 to the resistor R9809 and on to the mosfet Q9806. Pin 3 on Q9806 has the same voltage as the F9800 and nothing out the Q9806 drains.
This is the same on both laptops.
Does anyone have any ideas why?
What i was wondering was what test conditions Dadioh and others use e.g. I have just the logic board on the table with the power lead plugged in for some tests and power up the board for other tests with fans connected so i can tell its running.
I dont have the lvds cable connected usually but have tried once but it didnt seem to make any difference.
I was thinking maybe LCD_BKLT_EN isnt getting any voltage because i havent satisfied the neccessary requirements for the GPU's to enable the backlight and send the voltage to turn it on? Any ideas anyone ?

Thanks

you have to connect the screen before you will see voltage, try a smc reset a few times when connected...

 

[gratabb]

you have to connect the screen before you will see voltage, try a smc reset a few times when connected...

ok great thanks. I have a new LVDS cable on the way because it was shorting out so when it arrives i'll plug in the screen and re-test.

 

[cpufixer]

ok great thanks. I have a new LVDS cable on the way because it was shorting out so when it arrives i'll plug in the screen and re-test.

check the connector too...

 

[emin94h]

EMIN, POS on Ground, NEG on fuse, you should get .581 volts in diode mode on the WLED fuse. With power removed.
just like Louis.

What are you talking about? I'm not talking about "diode mode" I was checking the voltage in the backlight circuit. I've already told this to Louis in his comments were he didn't even answer that my multimeter doesn't have auto-range therefore it doesn't measure 0.xx (with a dot) only without it. I've already checked the fuse in diode mode, I got the reading 512 to ground (that doesn't say me anything) and the buzzer beeped both to ground and across the fuse, meaning that the fuse has continuity, meaning that the fuse is OK (not blown) so please stop ignoring what I wrote in my earlier post.

 

[gratabb]

check the connector too...

Ok so i have got the new lvds cable in and screen connected up. The backlight still doesnt work so here is what i found:
With the power cord plugged in the F9800 has 8v both sides, and Q9806 has 8v on the gate and source.

When i have the laptop running i have:
F9800 8v in and 2v out to the Q9806.
The Q9806 has 2v on gate pin 3 and a bit less on the source, and the drain pins have about 2v.
The wled driver also has 2v in and out
pin 40 on LVDS connector also has 2v.

Should the F9800 have different voltages in and out like this ? i think i read that the resistors pull down the voltage but does this sound right?

I was expecting at least 8v out the Q9806 drains, and 30v out the wled driver to pin 40.

Any more thoughts on this?
Sorry i had to write this quick so its not written too well !