820-3330B A1286 No İmage

tipoti

Member
There is sound but there isn't video. On 3rd and 4th legs of J9000, there were short circuits, I cleaned them and made another path. On 4th leg there is 3.3 volts but there isn't any on 2nd & 3rd. So, I backtracked and checked U9000. On its 2nd & 3rd legs, there are 3.3 volts but there is no voltage on lcd_pwr_en. On the same path there is no voltage on first leg of R9678. In this case, should I replace U9000?
 

2informaticos

Administrator
Staff member
No matter problem found on 820-3330 board, you need to resolder U8900 with leaded solder.
Is a preventive measure, which can also be related with your particular problem.

Do you get external video?

Check R9010/11, their traces and solders.
Post voltage and diode mode to ground at CLK/DATA lines.
Be sure video connector and cable are good; test with another LCD assembly.

BTW, use "pin" instead of "leg" for electronic components...
 

2informaticos

Administrator
Staff member
Does that mod survive to PRAM reset?

PCH needs to talk first with LCD through DDC bus, via U9270.
Check if that MUX chip is correctly controlled.
 

2informaticos

Administrator
Staff member
Pins 5/12 must be high, when iGPU enabled.
Of course 6/13 must be low at same time; discrete GPU disabled.
GMUX (U9600) is still in place?

BTW, no reason to measure video/backlight signals without LCD connected!
 

tipoti

Member
Before I made uma, device was turning on with a green screen. After the uma, there was no problem, it turned on. But, a piece of solder stuck on lcd pins and it caused it to short circuit, so I get no image now. SMC reset is enough to cancel UMA. I cancelled it, there are 3.3 volts on the 6th pin of U9270 but still I get no image, no light, nothing...
 

tipoti

Member
GPU was already malfunctioning but there was image. When UMA was cancelled, it turned on with a green screen as I stated but, I don't think GPU is the problem right now because there is no image, nothing. Before, GPU was offline and there was no image again. I cancelled UMA as you instructed.
 

2informaticos

Administrator
Staff member
You've said to have 3330 board (2012), not 2915 (2011).

Some information available here.
 

tipoti

Member
what does this mean
device turns on, there is sound, but no image and no light

image gone after being in this picture
 

Attachments

  • WhatsApp Image 2021-07-16 at 09.38.23-min (1).jpeg
    WhatsApp Image 2021-07-16 at 09.38.23-min (1).jpeg
    314 KB · Views: 6

2informaticos

Administrator
Staff member
That LCD connector MUST be changed.
Video cable could be damaged too, inspect it with microscope.
If GPU is still in use, check for external video.
 

tipoti

Member
i changed the lcd socket, I didn't think it had anything to do with it,
There is an image on the external screen.
 

2informaticos

Administrator
Staff member
"I didn't think it had anything to do with it"
It is damaged; do you really think that one made good contacts???
Post voltage for pins 4, 6, 7.

Video cable is still good?
Did you try known good LCD assembly?
 
Top