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820-01598 Stuck at 5V 300-400mA current draw

C

CGid

Member
Have a Macbook A2159
Board Number: 820-01598

Upon inspections there was a 320mA constant draw by TPS62180 (U6903)
I removed the chip and checked it and found it shorted, so it was replaced.

After replacing I have the following,

PPBUS_G3H - 12.3V
PP3V3_G3H_RTC - 3.310V
PP3V3_G3H - 3.250V, drops to 2.4V them back up to 3.250 (Cycling here)
PP1V8_SLPS2R - 1.8V (cycling just like PP3V3_G3H)
PP1V8_AWAKE - 1.8V (cycling just like PP3V3_G3H)


PPBUS_G3H - O.L
PP3V3_G3H_RTC - 0.652 kOhms
PP3V3_G3H - 23.7 Ohms to ground.

U7800 shows signs of heat under thermal camera. Any help is appreciated.
 
C

CGid

Member
After being disconnected from power since the time of posting it reads 21.2 ohms. so seems something is wrong here. Is voltage injection possible since it's not a dead short?
 
2informaticos

2informaticos

Administrator
Staff member
Injecting 4V will cause 200mA aprox; not enough to heat anything on the board.
A good thermal camera may point you to some small thermal signatures.
You may need to wait some time; remove CPU heatsink first.
 
C

CGid

Member
Just curious. Is there a reason diode mode is used over resistance? more just a general question. I'll have to order a replacement chip.
 
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