820-01958 intermittent behavior

[kjchatman]

i'm confused about this board. the battery doesn't charge and the fan ramps to full speed everytime. only one usb-c port works everytime and sometimes the other does. the board appears very clean with no signs of corrosion. Can this board operate without a working battery?

 

[2informaticos]

Machine gets very slow and loud fan, if no good battery is connected.

 

[kjchatman]

it's able to charge the new battery and it booted and worked fine but now it charges but it won't powe up anymore. I was able to use the apple configurator and that still didn't bring it back to life. ppbus is 13v and slp_sus_l is 3.3v but slp_sus_s5 is 0v

 

[2informaticos]

Forget PM_SLP_S5_L, is not relevant anymore.
Try again with charger alone (no battery).
Also test SMC reset.

 

[kjchatman1]

with charger alone the ampage will fluctuate but it never gets high enough to boot. then it just sits at 20v 0.00a. how to test smc reset?

 

[kjchatman1]

5 ohm resistance to ground on L8100. is that a short?

 

[2informaticos]

Pufff, looks too low for RAM power; compare with good board.

 

[kjchatman]

would that rail short keep the board from powering up?

 

[2informaticos]

Of course, incorrect resistance to ground triggers the protection of that power supply.
Missing its power good signal, will then break the power on sequence.

 

[kjchatman]

190 ohms on a working board. i'll inject 1v and hope for the best

 

[2informaticos]

Remove CPU heatsink first.
CPU receives the same voltage too.

 

[kjchatman]

it's only drawinng .056 amps

 

[2informaticos]

1.3V is safe voltage and should get 0.25A aprox (for 5 ohm).
However, this means less than 0.4W, impossible to heat something.
An IR cam may help; basically, need to distinguish between CPU and a RAM chip.

 

[kjchatman]

1.35v draws 0.041amps

 

[2informaticos]

Then you have much higher resistance than 5 ohm to ground.
In such case, removing chips is the only way.

BTW, I hope you didn't limit your PSU current at all.