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820-01700 - PP2V5_NAND_SSD0 at 12ohms

overshoot

overshoot

Member
Hi,

I was getting 5V with no amperage.

PPBUS was had a 20ohms resistance to ground which lead me to find the shorted part.
I could see that visually U9580 was burnt on a side and a solder ball was lying around.
Took U9850 and PPBUS short is now gone.

However I'm getting 12ohms resistance to ground on PP2V5_NAND_SSD0 which is worrisome.

Can someone confirm what resistance I should be getting on this rail please?
I guess that's game over if the SSD is out.

Is it safe to inject 1-2v on that rail to see what gets warm or too risky for the SSD?
 
2informaticos

2informaticos

Administrator
Staff member
1-2V into 12 ohm probably doesn't help; nothing will heat there.
Unless some avalanche proces appears and resistance to ground drastically drops.
 
P

piernov

Moderator
Staff member
The NAND chips are most likely dead. Happens very often when something goes wrong with the SSD power rails.
Thermal camera could still help see something warming up slightly.
 
overshoot

overshoot

Member
Thanks for your replies guys!

I've tried 2V and only the SSD area gets warm (40 degrees).
Nothing really warms up in particular, not a cap at least.
The current goes to .3-.5A even though the limit is set at 1A.

I have to take U9580 off a donor board from an icloud locked 15" 2018 board which works.
With this 12ohms readings, do you guys think it's worth trying?

At least, can anyone confirm which resistance measurement I should be getting on that rail please?
 
2informaticos

2informaticos

Administrator
Staff member
Being the same U9580, very likely board has the same power specs for SSD area.
You may expect some difference in diode mode reading.
However, if good board has more than 050, good enough to denote incorrect value on your board.
If you get less than 020, then 012 could be also correct.
 
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