Help please 820-3435-b no image

[RESQ-MYTECH]

Morning guys.
Logic board 820-3435-B. no image. screen illuminates. no chime ( may be turned off). Logic board is immaculate.... to immaculate TBH.
Tested so far:-
Pins 18/19 J8300 PP3V3_S0SW_LCD_UF =0.00v
L8304 Pins 1/2 =0.00v
R5670 not fitted
U8300 pin 1 EDP_PANEL_PWR= 0.00v
pin 2/3 PP3V3_S5 =3.334v
pin 4/5 PP3V3_S0SW_LCD_R =0.001v
pin 6 GND =OK
J8300 pin 14 DP_INT_HPD_CONN =0.00v
pin 24 DP_INT_ML_P<0> =0.001v
pin 24 DP_INT_ML_N<0> =0.00v

Seeing as the screen is illuminating I have not tested pins 3/4 on J8300

Now, I am assuming that EDP_PANEL_PWR needs to be present to activate U8300 but reading the shematic ( probably incorrectly) this leads back to pin 765 on the CPU. using Landrex I do not see anywhere that I can test for EDP_PANEL_PWR. Also.... might be me and it being an early morning, I have done a search on the forum for 820-3435 no image even down to a straight 820-3435 search and apart for a post that has Duke on it where it is surmized that the CPU is dead, I have found nothing with reference to this issue on this board.

Has anyone got any pointers or is it in fact a "gonna"?

Many thanks in advance.

 

[2informaticos]

"J8300 pin 14 DP_INT_HPD_CONN =0.00v"
High level means LCD panel correctly recognized.
LCD needs to get voltage at pins 18/19 of J8300 in the first few seconds at least, in order to put high DP_INT_HPD signal.
Strange to have backlight in your case...

Check first if has USB activity; using OSX pendrive with link LED is the best option.
You can also try PRAM reset, see if chime comes too.

I recommend to test known good (compatible) LCD assembly.

 

[RESQ-MYTECH]

Hi 2informaticos . OK above testing was done without the screen attached. I did do a PRAM and SMC reset prior to doing the probing, but did the PRAM one again. I also reconnected the screen.
Updated info:-
Still no chine.
Connected a HDD that I have got multiple OSx on and the LED flashes. I also plugged in a keyboard and used to do the PRAM and SMC reset. As to the PRAM the logic board restarted and the SMC the LED on the adapter changed from orange to green and back to orange so I can clarify the USB side of things are working.
Pins 18/19 of J8300 with screen connected goes to 3.331v and stays at that voltage.
Pin 14 goes to 2.63v and stays.

I have an MBA here that is a A1370. Is the screen usable with that of the A1465? Just for diagnosis puroses.
Thanks.

 

[2informaticos]

3435 uses display port.
Check schematic of your A1370 board and compare LCD connectors.
This will not assure 100% compatibility however.

"Pin 14 goes to 2.63v and stays."
You had 0V before...
Do you get image now, even no backlight?

 

[RESQ-MYTECH]

HI 2informaticos . Hope you dont mind but i have sent you a PM.

 

[RESQ-MYTECH]

Hi all. After listing the above results and following what 2informaticos suggested, I can comfirm the issue has be diagnosed and awaiting customer confirmation for repair. The issue is the screen unit. Thank you 2informaticos for your assistance. I have sent you an email but I will be posting up the issue with the MBP in another post.