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820-00239 flashing question mark

Y

Yoel Ren

Member
came in for liquid damage, clean it, and have foldermark questionmark, run slowly with max fan speed, disk utility show nothing on internal, terminal diskutil list doesnt show anything internal ssd too
lifeboat connector is attached, I saw video from paul daniel about connecting missing traces from R9350 to the probe point infront of it, so I did, and still the same question mark folder, then I found out that the PPVIN_2v7NAND_LB is shorted to ground, I have tried removing c9402, c9403, c9400 c9404 c9401, but short is still present..
 
2informaticos

2informaticos

Administrator
Staff member
PPVIN_2V7NAND_LB comes from PPBUS_G3H.
So you have a problem with lifeboat connector for sure.
Board shouldn't start at all, with PPBUS_G3H shorted to ground.
So J9600 doesn't close pins 43/44.
Is possible to have other broken connections too.

However, you should eliminate the short first.
If you get the same ohm value to ground at L9400, then remove Q9401 and check again.
I recommend you to pray a lot, if you want to have a good nand still.
 
2informaticos

2informaticos

Administrator
Staff member
Why to inject on PPBUS_G3H if no short there???

On your board, PPVIN_2V7NAND_LB doesn't make contact with PPBUS_G3H anymore.
If you still have short on PPVIN_2V7NAND_LB, there is the point to inject.
But I was expecting exact ohm value there, as in L9400 too.

You can have the short on J9600.
Remove lifeboat top plate and check again.
 
Y

Yoel Ren

Member
resistance to ground with red probe on ground L9400 : 3.7 kohm
11.5 k ohm with black probe on ground
removing j9600, but still short on PPVIN2v7nand_lb
purchasing bench power supply..,a question please, for injecting voltage, the psu must be regulated psu right ? thanks
 
2informaticos

2informaticos

Administrator
Staff member
You need regulated power supply, with high current capability.
I already posted some links on the forum.
You can choose 24V/20A, 12V/40A, or even cheap DPS modules, like DPS5020 from Aliexpress.

Follow the PPVIN_2V7NAND_LB trace on the board.
J9600 looks good, no damage on power pins?
Check C9401-04; start with C9402/03...
 
Y

Yoel Ren

Member
so i inject 2v there, and my jumper at r9350 disconnected, I tried reconnecting r9350 and the probe point in front of it, now there's no short, but ppvin_2v7nand_lb voltage is 13v, and cycling every few second, macbook still alive, c9401-4 looks fine no short
 
2informaticos

2informaticos

Administrator
Staff member
Any pulse at L9400?
Do you get 13V at pin 1/R9350?
Be sure PPVIN_2V7NAND_LB trace has continuity on all its components.
 
Y

Yoel Ren

Member
i have pp3v3_s5_ssd, so my next option is to only replace u9300, if still can't can nand be replaced?
 
Last edited:
2informaticos

2informaticos

Administrator
Staff member
I exactly don't know what you did there and the initial state of your board.
This board could be waste of time to go ahead now...
 
Y

Yoel Ren

Member
I salvage the cd3215 and u7800 before, but i think its just a waste to go to trash, i can still use this machine as lcd tester..
After i reassemble all salvaged chip (cd3215 and u7800),
Ppdcin 5v but looping at all port except at bottom of j3300 which i think correspond to u3100, i have pp3v3_g3h
, i have diode mode all 4 cd3215 and all have at least 0.400v at 3 ldo output 1v1 1v8 3v3.. anything i should check?
 
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