A1990 No power

[ronaldo]

Hi, I have an A1990 board 820-01041-A, no corrosion or liquid.
The NANDs on the left (immediately are getting warm after 10 seconds or so, then get hot - no power. The trackpad was clicking, after trying DFU revive it doesn't click any longer.

Board is taking 20V and bouncing between 0.1A and 0.7A
PPBUS_G3H is present bouncing between 10.6V and 12.5V
PP2V5_NAND_SSD0 is shorted to ground
PP1V8_SSD0 is present 1.8V

I was reading on RepairWiki that what is important is that PPBUS_G3H doesn't go direct to the NAND - pardon my stupid question but how can one check this? Would the PP1V8_SSD0 and PP2V5_NAND_SSD0 lines be ~12V?

I will check tomorrow under thermal camera once I am back in the shop, with my novice knowledge does this mean SSD is dead?

 

[2informaticos]

Very likely one NAND chip is shorted to ground.
You can try injecting 1V and see what gets hot there.

 

[ronaldo]

3 SSD Nands are getting warm/hot, and there was scorch marks on U9080.
PP2V5_NAND_SSD0 is 1.5Ohms, removing U9080 and U9000 has made no difference to this resistance.
After injecting 1V without the two SSD controllers present nothing gets hot




So would it be accurate to say at this stage one or more of the SSD NANDs have internal short? Or the only way is to take U9080 U9000 from working board and test?

 

[2informaticos]

If still short to ground at L9080/81 after removing U9080, at least one NAND is bad.

 

[ronaldo]

Thanks, so this board is now a donor I guess. Shame.