A1990 820-01041-A no video

[pascable]

Hello everyone

First of all, thank you for your kindness, I do not speak English and I am using Google Translate to write my message to you.
Hope you will understand me and can help me.
Logic board 820-01041-A MacBook A1990.
It starts up without problem, boots very well on an external screen but no video display on the MacBook screen, no backlighting.
I am not a great specialist in electronics but I noticed that at pins 43 (0V), 44 (0V), 45 (0V) and 46 (5.5V), of the J8500.
Is this normal because of another line?
If you can guide me what to check, thank you very much.

Sincerely, Pascal (France - Reims)

[mon2]

Re: A1990 820-01041-A no video

hello.

What is the history of this computer? Any liquid damage ? Look for red dots on the logic board which indicate that liquid was spilled.

No display even if you use a flashlight on the front of the screen ? Can you see the apple logo with the flashlight?

[pascable]

Re: A1990 820-01041-A no video

No trace but liquid received.
Pa sde backlight, I watched with a lamp.

[pascable]

Re: A1990 820-01041-A no video

Could the fault come from a line other than:
PP3V3_S0SW_LCD (44)
PP5V_S0_ALSCAM_F (46)
PP5V_S0SW_LCD (45)
These are the pin numbers of the J8500.

[mon2]

Re: A1990 820-01041-A no video

check the attached and post your values.

added another check point - check the rail BEFORE the current sense resistor.

where was the liquid damage ? has it been repaired?

[pascable]

Re: A1990 820-01041-A no video

For 1 on C8509 (U8500) = 0V
For 2 on C8510 (U8501) = 3.3V
For 3 on R8520 pin 2 = 0V
For 3 on U8510 1 = 3.38V
For 4 on U8501 2 = 3.38V

[mon2]

Re: A1990 820-01041-A no video

Please confirm that your results are:

For 1 on C8509 (U8500) = 0V
For 2 on C8510 (U8501) = 3.3V
For 3 on R8520 pin 2 = 0V
For 4 on U8510 1 = 3.38V
For 5 on U8501 2 = 3.38V ; is this the reading on pin 5 of U8501 ?

[pascable]

Re: A1990 820-01041-A no video

I watch this in the morning and first of all, thanks for your help.
See you later.

[pascable]

Re: A1990 820-01041-A no video

On my board there is an error. Pin 5 is denoted 6. It goes to pin 1 of the R8520 and it has 0V.
C8509 = 0V (no short circuit to GND)
C8510 = 3.38V + 3.38V on the 3 and 1 of the U8501
R8520 (without component, just solder point):
On the 1 = 0V
On the 2 = 0V
On the 3 = 0.2V not stable
On the 4 = 0.1V not stable
U8510 on pin 1 = 3.38V
U8501 on pin 5 (noted 6 on the boardview) = 0V

[sherifbekhit]

Re: A1990 820-01041-A no video

Hi friends
I cant found spi flsh chip
Any body can help me plz.

[pascable]

Re: A1990 820-01041-A no video

What is "flsh spi chip"?
Apple reference please and I will help you.

[wws911]

Re: A1990 820-01041-A no video

Hey have same kind of issues. Apparently liquid damage.. we're do I check