820-00138-A Not outputting PPVOUT_S0_LCDBKLT

[Flippers McCoy]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

hello,
was your problem solved? i have here same mainboard with exactly same problem...no output to LCDBKLT

Haha, it was so long ago I've got no clue at this point.
What's your board number? I can see if I can help out

[CornholioGSM]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

thank you for reply
My mobo is 820-00138-A...visualy looks same as 00163-A...but not possible to find correct boardview
Soo where to start.
On lcd connector is not short on Pin1 (LCDBKLT) and 0V.
On Fuse 7700 i have 12.5V on both side.
On fet Q7701 is nothing - 0V - not shorted.
On U7701 pins 5,18 = 5V, on 19 0V.

[piernov]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

00163 has a dGPU, 00138 doesn't.
00138 boardview is not available, you have to look at either 3662 or 00163 depending on the area.

Give more info about the history and the state of the machine. Confirm you have image on the display, and confirm you are using a 2015 display for sure.

[CornholioGSM]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

i dont know nothing about history mainboard looks undamaged and no signs of water.
It boots up into system but no backlight

[Flippers McCoy]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

What are you getting on pin 17 of U7701?

[CornholioGSM]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

sorry for deelay...i have nothing on pin 17

...and nothing on LCD_HPD

EDIT...so i have found that i have 1V on pin 3 (DP_IG_A_HPD_L) on Q2010...so maybe is Q2010 dead?

[CornholioGSM]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

for correct...LCD_HPD is signal from LCD panel ?

[Flippers McCoy]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

for correct...LCD_HPD is signal from LCD panel ?

Yes, LCD_HPD does come from the LCD panel.
With that in mind, make sure you're doing all this testing with the LCD panel plugged in!

sorry for deelay...i have nothing on pin 17

...and nothing on LCD_HPD

EDIT...so i have found that i have 1V on pin 3 (DP_IG_A_HPD_L) on Q2010...so maybe is Q2010 dead?

Q2010 is probably not dead, although it could be. I believe that DP_IG_A_HPD_L needs to be 0v to turn the backlight on. LCD_HPD needs to be higher than 0v to allow Q2010 to work properly (short DP_IG_A_HPD_L to ground).
So the question now is why is LCD_HPD 0v?
If you're testing with the LCD panel plugged in there must be a short to ground somewhere on LCD_HPD

[simplylcd]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

did you find the issue I have an 820-3662 MB Retina with the same issue

[BeertjeBas]

Re: 820-00138-A Not outputting PPVOUT_S0_LCDBKLT

Today working on a 3662 board. After a long search i found a short in Q7706. Pin 3 was 12.6v. This should be around 8.6.