820-00923 SSD issue and no internal display

[iganas]

Hi, new here!

Got a A1706 board that had minor liquid spill by the display connector on the screen side, as well as around BIOS chip.
After a new display cable and touch-up of suspicious components, the symptoms are as follows:
- No internal display with known good screen, external display works
- Draws 20v 350-600mA
- Takes nearly two minutes to boot up the screen and then another minute to display folder icon
- PP3V3_2V7_NAND = 0v
- PICCOLO_IUVD = 0v
- PP3V3_2V7_NAND_VCC = 0v
- PP1V2_SSD_HOT = 0v
- No obvious corrosion left on the motherboard nor probe points
- Nothing flaring up on thermal camera

Do these symptoms sound familiar and what would be the next logical area to test?

Thanks for your assistance

 

[2informaticos]

First of all, welcome to the forum!

Folder icon displayed means SSD is not detected; normal, as no voltage on it.
Missing image on internal LCD is very likely bad CPU eDP output.
Is a classic fault after liquid spill on video connectors.

Post diode mode to ground on SSD power rails.

 

[iganas]

Can eDP signals be measured with no screen attached? And what should I measure against?

PP1V8_SSD_COLD - 0.6
PP0V9_SSD_FIXED - 0.9
PP1V2_SSD_HOT - 0.9
PP1V8_SSD_HOT - 1.1
PP1V2_SSD_COLD - 0.7
PP0V9_SSD_REG - 0.15

 

[2informaticos]

You can check diode mode to ground on data lines; w/ and w/o LCD connected (no power, of course)
But voltages will require LCD detection to be maintained.

As you also have missing SSD voltages, the problem is not only about video.

 

[iganas]

You can check diode mode to ground on data lines; w/ and w/o LCD connected (no power, of course)

What voltages should I expect on the probe points?

As you also have missing SSD voltages, the problem is not only about video.

I am aware these are two different problems. Do the diode readings give any hints at what to measure next?
Any reason to suspect U8600?

 

[2informaticos]

You can only check for voltages at J8500 in the first few seconds, if the screen is not connected.
After that, PCH will disable the voltages; because DP_INT_HPD stays low.

 

[iganas]

Do my SSD rails' diode readings give any hints at what to measure next?

 

[2informaticos]

Check J9600 connector.

 

[iganas]

J9600 looks clean.

Just noticed that PP3V3_S5_SSD is at 0.76v.
Does that point to U9300 Piccolo chip?

 

[iganas]

Check J9600 connector.

Does the cap need to be present for it to function/enable power to the SSD? I believe someone before me has removed it. The connector itself looks intact

 

[2informaticos]

That cap is the heart of the Lifeboat connector!.

 

[iganas]

That's great!.

With the cap on, all these voltages are on point for the first 2 minutes before the screen boots up:
PP1V8_SSD_COLD
PP0V9_SSD_FIXED
PP1V2_SSD_HOT
PP1V8_SSD_HOT
PP1V2_SSD_COLD
PP0V9_SSD_REG

However once the folder icon appears, they all drop to 0v.

What could that indicate?

 

[2informaticos]

Try to boot USB macOS and check what appears in Disk Utility.

 

[iganas]

820-00923 - MacBook Pro Touch Bar Question Mark Folder

Hello, I have a MacBook that is stuck on the question mark folder. With the motherboard fully out and charger plugged in: 20 volts on charger, 0.43 amps PPBUS_G3H = 13.10 volts PP3V3_S5_SSD = 3.3 volts PP0V9_SSD = 0 volts PPVIN_2V7_NAND = 13.10 volts PP1V2_SSD_HOT = 0 volts PP1V8_SSD_HOT = 0...

boards.rossmanngroup.com

I'm getting the same issue of non-responsive keyboard as mccafe had.
Cannot perform resets nor hold Alt for boot selection.
USB key doesn't flash not even once during boot, nor when the folder icon appears

 

[2informaticos]

If someone else messed up with the board before you, rhis can be a nightmare.
Some technicians intentionally rip off components, or make damage on the boards; when they cannot fixed them.