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MacBook Air a1465 820-3435 green light, boots, chime, but no backlight.

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pezter22

New member
I’m new to repair. I am a laid off newspaper photographer looking for a transition to a different career. I’ve done pretty well so far. I started with G4 Powerbooks and progressed to 2010’s MacBook Pros and Airs I usually buy broken MacBooks on eBay to learn, practice and repair. My latest purchases has been a 2013 MacBook Air 11” a1465 and 2011 13” a1369.

My question today is with the MacBook Air 11” with the 820-3435 board. I know the MacBook Air no backlight issue is not new, but I could use some guidance.

I get green light, boot and chime, but no backlight. I do get an image and can see a blinking folder if I shine a light behind the screen. I thought it would be a simple change of U7701, but no. I still have no backlight. The screen connector cable has no damage, nor is there damage to the LVDS connector on the board.

LVDS connector pin 18 and 19 - 3.32v - pin 3 and 4 - .001v
C8317 - pin 1- PPHV_S0SW_LCDBKLT - .001v
D7701 - pin 2 - PPHV_S0SW_LCDBKLT - .001v
pin 1 - LCDBKLT_BOOST - .001v
C7799 - pin 1 - PPHV_S0SW_LCDBKLT - .001v
L7701 - pin 1 - PPVIN_S0SW_LCDBKLT - .001v
pin 2 - LCDBKLT_BOOST - .001v
F7700 - pin 1 - PPBUS_G3H - 8.58v
pin 2 - PPVIN_S0SW_LCDBKLTFET - 8.58v
R7715 - pin 1 - BLK_EN - .001v
R7731 - pin 1 - BLK_EN - .001v

There is continuity and no broken traces between D7701 pin 1 to L7701 pin 2 or the test pad near by.

I know there is something I am missing, but can’t seem to find the issue. Any help would be greatly appreciated.
 
2informaticos

2informaticos

Administrator
Staff member
First of all, welcome to the forum!

If you write a signal name, or power rail, no need to mention component and pin where to check; we will find it.
And the post is more easy readable.

Check voltage for EDP_BKLT_EN and BKLT_PLT_RST_L.
If both present, post Q7706 voltages.
 
2informaticos

2informaticos

Administrator
Staff member
Really strange, as you get image.
Check EDP_BKLT_PWM too.
Be sure SMC_LID is steady high, just in case.
Do PRAM reset 2-3 times.

Post diode mode to ground at K/D7701, w/ and w/o LCD connected.
 
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pezter22

New member
I did the PRAM rest no change. I still have an image, but no backlight.

EDP_BKLT_PWM - 1.478v
SMC_LID - 3.43v

diode check on D7701 produced OL on both sides with and without LCD connected.
Unsure what "K/" means

I replaced D7701 from a a1466 820-3437 board that share parts. On that board in diode mode it read .561. However when I placed it on the 11" board it again read OL on both sides. I guess that brings me closer to the issue.
 
2informaticos

2informaticos

Administrator
Staff member
ALWAYS measure diode mode with red probe connected to ground.
I suppose you will get correct readings on both boards then.
You cannot get OL measuring in correct way!

If you pay attention to schematic, D7701 has two terminals; A (anode) and K (cathode).
 
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pezter22

New member
Yup. Measured with Red as ground on screw hole nearest the area. That’s how I got the .561 on the donor board. Once I soldered the diode on to the board, I again got the OL on both sides. I even changed my test leads on my Fluk. Similar reading.

I checked a photo of the board before I changed anything and do have proper orientation.
 
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pezter22

New member
I don't know with this board. I removed everything on this line that has been giving me an OL. I wicked up the solder and check the pads for continuity. I got tone on each connected pad. I checked Olms on each piece and got good readings. I resoldered the pieces and OL again.

I again removed each piece, wicked up the solder and changed my solder and only placed the D7701 onto the board. OL again.

I do check other components to see if I get a proper diode reading and I do. It's just this line that I get OL on all pads with the components soldered onto the board.

These are the pieces I removed - all associated with either
PPHV_S0SW_LCDBKLT
LCDBKLT_BOOST

L7701
D7701
C7799
C7797
C8317

I appreciate the help, but I may just move on from this board unless something new can be suggested. This one baffles me.
 
2informaticos

2informaticos

Administrator
Staff member
OL means no connection with other components.
What do you expect removing even more components???
Please, try to pout a logic on your job!

"only placed the D7701 onto the board. OL again"
This is indeed VERY good reading, as no other component is connected there to ground; you already removed all.

You need to find why don't get similar readings like in other board.
U7701 is connected with both pins of D7701.
It has lot of internal components, which makes it indicates something in diode mode; IF you correctly check, with black probe on pin and red probe at ground.
 
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pezter22

New member
I understand that, but when I place D7701 back on the donor board, I get a reading (one cap missing). Again I am placing red probe on a ground point (actually several) while in diode mode. And it is the correct setting on my Fluk. I do get readings on other locations, just not on those lines. I will try again with the components back in their location.
 
2informaticos

2informaticos

Administrator
Staff member
Did you check continuity from D7701 to U7701?

All components (especially U7701) must be soldered on the board, when you check diode mode to ground readings.
 
P

pezter22

New member
Okay. I will place everything back on in the morning and recheck. I will check continuity with D7701 to U7701. Thanks again for the suggestions.
 
P

pezter22

New member
Back on track. Please remember I am a newbie. When I went to check continuity with D7701, it lifted a bit. That would explain the OL. I reseated it and now have proper readings on everything.

PPHV_S0SW_LCDBKLT - .007

D7701 in diode mode
with screen connect - .591 and .405
without - .602 and .409

LCDBKLT_BOOST - .007

Voltages at Q7706
PPVIN_S0SW_LCDBKLT_FET - .006

LCDBKLT_EN_DIV_L - 8.32

PPVIN_S0SW_LCDBKLTFET - 8.57
 
2informaticos

2informaticos

Administrator
Staff member
"PPHV_S0SW_LCDBKLT - .007
--------------
LCDBKLT_BOOST - .007"
What these readings are?
Diode mode can't as, you don get same readings on D7702.
And voltage, I don't think; unless you like (out of reason) to check voltages with 3 digit after zero...

Do you still get image?
Remove Q7707 and tie together pads 1 & 3.
Check D7701 voltages again.

Keep LCD connected.
 
P

pezter22

New member
I still get image, but no backlight. Blinking folder appears only with flashlight on back of screen.

I removed Q7707 and jumped pads 1 & 3.

Voltages at D7701 with screen connected

LCDBKLT_BOOST - .016
PPHV_S0SW_LCDBKLT - .016
 
P

pezter22

New member
Sorry for the delay, day job...

Q7707 with jumper on pads 1 & 3

Q7706
LCDBKLT_EN_DIV_L - 8.31
PPVIN_S0SW_LCDBKLTFET - 8.58
PPVIN_S0SW_LCDBKLT_FET - .101

F7700 is good.
PPBUS_G3H - 8.58
PPVIN_S0SW_LCDBKLTFET - 8.58
 
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