820-01700 comes only backlight. please help

[Dozer]

got this device with a strange problem. connecting batterie, open lid, connecting power .

20V, amper is rising up until about 2.8A
then it switches to 19.8V like always, display backlight is coming up and that is all !

i checked the whole board no water damage to see or any other strange things, hecked the edp-connector with the mac edp-meter, all ok.
checked the NAND power 2.52V both sides, checked external display, same hdmi is detecting the signal, monitor turn on but no picture to see only a light black

reballed the U9850 no change

what is the next step usually after turn on backlight?

 

[Dozer]

I only need user-data. I tryed to set Target mode but nothing. PRAM reset seems not possible and there is no chime

 

[Dozer]

it turns on like described and from turning on backlight after 34 seconds it turns off and all starts from beginning, that is cycling.
I checked the NAND power but this is without interuption steady 2.52V

I found out still another intresting thing. by connecting the touchpad the display comes up only for about 1 second. i thought the pad is faulty so i replaced it and the cable but result the same, with touchpad 1 second, without 34 seconds

 

[2informaticos]

Still restarts if you turn it on pressing T key?
Even no image, check if its SSD is detected in another MacBook.
You may need to use thunderbolt capable cable.

Tried DFU revive?

 

[Dozer]

thanks for your replay.
still restart (all 34seconds) by pressing T key or not
I will try to get it in DFU mode, is it needfull to connect the trackpad?

 

[Dozer]

connecting a real known DFU working thunderbolt cable in the left USB port near trackpad and connecting battery and shorten SWK003 by plug in power shoul do this yes?

 

[Dozer]

get DFu but during revive step 4 half way it turns on, only backlight, then I get this

and it stays in this mode (on only backlight, dont turning off) after disconecting thunderbolt cable it turns off. after that it dont turns on for 34 seconds, it do nothing. get back in DFU mode this time with conected trackpad. step 4 half way display turns on for a second then i get this symbol like a lock.

but now it is cycling again display on 34 seconds, off and so on....

 

[Dozer]

before i wrote her , 2 weeks ago i got a working a2141 i replaced the board with this one and got a sign battery empty, but only one time all the other trys were the same like this and before replacement. i checked the good board in the case of this board there was all ok.

 

[2informaticos]

Padlock sign means DFU has been completed, without errors.

Did you test the board with a charged battery?

 

[Dozer]

yes I had last week a good device only for some softwareupdates here. i replaced the mainboard but there it is cycling as well.

I load up a video of the cycling: https://lrzt.de/video/cycling video.mp4

I just think is it worth to solder out the NANDS for testing with a P13 if they are readable. This client has a lot of problems without the data. if the NANDs are damaged all the coming work will be without reason.

but my feeling says me that can be possible to bring back to live anyhow, but i have no idea what else I can do. Need realy help here please.

 

[2informaticos]

Did you test again starting in Target Disk mode, after DFU revive was completed?
Check if its SSD appears on other Mac.

 

[Dozer]

PP0V9_SSD1 = 0,9V
PP1V8_SSD1 = 1.8V
PP2V5_NAND_SSD1 = 2.52V

SSD1_VR_P2V5_PGOOD 2.4V
SSD1_VR_P2V5_PGOOD 1.8V
SSD1_OCARINA_RESET_L 1.77V
SSD1_CLK24M_01 present and nice wave
R8640 101 Ohm

C8701, C8702,C8703, C8704 both sides in diode mode "good" values from about 0.3
C8601, C8602, C8603, C8604 both sides in diode mode "good" values from about 0.3
C9101, C9102, C9103, C9104 both sides in diode mode "good" values from about 0.3
C9401, C9402, C9403, C9404 both sides in diode mode "good" values from about 0.3

R9140 and R9340 have the right value of 50 ohm and left and right in dode mode about 0.4 on both is a nice wave clock to see

U9300
C9314 pin1 = 0.9V
CC904 pin1 = 1.8V
C9350 pin1 = 2.52V
C9301,C9302, C9303, C9304 both sides in diode mode "good" values from about 0.3
R9340 have the right value of 50 ohm and left and right in dode mode about 0.4 on both is a nice wave clock to see


U9200
C9249 pin1 = 2.52V
C9212 pin1 = 0.9V
CC901 pin1 = 1.8V
C9201, C9202, C9203, C9204 both sides in diode mode "good" values from about 0.3
R9140 have the right value of 50 ohm and left and right in dode mode about 0.4 on both is a nice wave clock to see

 

[Dozer]

@2informaticos you are a genius!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

after again target mode the disk is apearing, saved the data and yipeeeeeeeeeeeeeeeee! thanks alot for this hint. that is sooo great. VIVA ESPANIA !
case is closed.