820-00840 Not working if battery connected [SOLVED]

[nik1981]

Hello, I'm stuck as I have an A1708 which powers up fine on the charger alone but won't boot if the battery is connected.

I've tried a known good battery but still no change.

On USBC alone, F7000 is 13v
On Battery and USBC F7000 climbs from 11v to 12.96v and drops back in a cycle roughly every 6 seconds.
On battery alone F7000 sits around 10.6 and very slowly drops

Resistance on R7061/62 + R5438 + R5439 are all as schematic.

Q7065 diode mode
from pin 5 to pins 1-3 is .219v
from pin 4 to pins 1-3 is .634v

I'm not sure where to check from here

 

[2informaticos]

Check R6905 first; must be 2.2 ohm...

 

[nik1981]

Thank you for the reply 2informaticos.

R6905 is reading 2.5 ohms while on the board

On a known good board, my multimeter shows 2.5 on that one also so I think my meter is just slightly out

 

[2informaticos]

The value is correct.

Do you get 3V3_G3H with battery alone (no charger)?
Did you check R7021/22 too?

Check for corrosion at J6951.

 

[nik1981]

Yes I get 3.344v for 3v3_g3h on battery alone

Yes I forgot to mention I checked R7021/22 and they're both as 1.3 ohms

J6951 looks clean inside and around it

 

[2informaticos]

Any fault history available?

 

[nik1981]

No, the MacBook came in with a non genuine battery but that seems to work.
No history of liquid etc. Just wouldn't power on one day apparently.

I disconnected the battery and tried with just the charger and it turned on as if nothing had happened. reconnected the battery and two others and it won't start.

 

[2informaticos]

Start with charger only and connect J6951 once logged into macOS.
Tight battery screw first, of course.
Check if battery is detected correctly then.