A1707 2017 LCD Dark after Liquid

[mon2]

Re: A1707 2017 LCD Dark after Liquid

Attached.

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

R8442 0.0020V
C8470..... al points same 0.0020

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

All measurements without a display connected

[mon2]

Re: A1707 2017 LCD Dark after Liquid

Display needs to be connected.

Remove all power.

Check the resistance to ground of PPVOUT_S0_LCDBKLT (red meter probe) & black meter probe to ground. Checking for a low resistance which can cause this rail to be pulled down OR even shut off due to an excessive load (current draw).

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

Does the display have to be connected for all measurements? Then I have to start all over again

[mon2]

Re: A1707 2017 LCD Dark after Liquid

Yes.

Connect the display but do not power up.

Meter in resistance mode. Check the resistance to ground on PPVOUT_S0_LCDBKLT.

Is it very low in resistance? If yes, then this needs to be fixed.

If resistance reading is high then proceed to power on and check if the voltage of PPVOUT_S0_LCDBKLT is high enough to light up the LEDs in the display.

Voltage of PPVOUT_S0_LCDBKLT ?

If low voltage on PPVOUT_S0_LCDBKLT then check if the backlight IC is being ENABLED.

Voltage of the backlight enable pin?

The points to test are in earlier posts above.

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

ok thx

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

i have pin43 to pin 1 4M ohms
measured as shown in the video by Rossman How to fix a black screen on my Touchbar MacBook Pro...

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

I have at U8400 pin 1 and 2 0,1Volts

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

Everything works on the external monitor

[mon2]

Re: A1707 2017 LCD Dark after Liquid

Post the voltages for:

1) R8444 & R8445, pin # 2. This will confirm that U8400 is being powered.

These are the VDD Digital & VDD Analog, respectively, power rails.


2) R8442, pin #2 = Enable pin voltage for U8400.

3) Q8400 mosfet - see attached. Need the voltages on:

pin 4

pin 3

pin 1-2-5-6 (measure any of these pins)

The voltage @ pin 4 should be the same as the voltage on fuse F8400, pin 1 (unless fuse 8400 is blown due to an excessive current draw).

[Strolch]

Re: A1707 2017 LCD Dark after Liquid

ok