820-3115 Not always charging battery

[nik1981]

I have an 820-3115-B with a intermittent fault.

It always turns on with a charged battery but doesn't always charge the battery.
When it doesn't charge, theres no green or orange light.
When it does charge, it shows orange light as normal.

I've noticed that if its in a charging kind of mood, PPBUS_G3H is 12.42-12.5v
If the charger is removed when its 12.5v, PPBUS_G3H instantly drops to 12.02v and sometimes drops to 11.4v ish

If the charger is plugged back in and PPBUS is above 12v on the battery, PPBUS jumps to 12.5v then drops back to late 11v or early 12v and slowly climbs up to 12.5v

If the charger is plugged back in and PPBUS is low.. like 11.4 or something, it won't light the magsafe but will eventually creep up PPBU to the 12v+ mark and start charging etc

I was thinking SMC issue or Q7055 after reading previous posts but want other opinions before I remove anything.

Second battery tried is known good but doesn't change the behaviour.
Charger is my 85w original


Running off the battery only, PPBUS_G3H is 12.04 in S5.. then when I power on the MacBook. It actually turns on fine but PPBUS drops to 11.4-11.6v instantly. If i then plug in the charger, it won't charge or light up the magsafe until one of two things happen.. either PPBU_G3H creeps up to 11.84-11.85v and then the charger comes on and it jumps to 12.5v or if it doesn't creep up, if I turn off the MacBook, it usually initiates the voltage creep up to 11.84v-11.85v at which point it jumps to 12.5 once it sees the 11.84v

 

[JohnB8812]

The voltage drops because the battery is not fully charged which is normal. What is your exact voltage on PPBUS_G3H with just the charger now battery? Check resistance between pins 17/18 and 27/28 of the ISL6259.

 

[2informaticos]

Try first another DCIN board.
Battery is not charging if no Magsafe light.

Look around U6900/01; check solders, traces...

 

[nik1981]

JohnB8812 Exact voltage on PPBUS_G3H with the battery removed, just 85w charger and the MacBook turned both off and on is 12.48v-12.49v

On ISL6259 (U7000) resistance between 17/18 is 2.8 - between 27/28 is 20 ohms which both seem fine I think.


2informaticos I'm checking U6900/U6901 now for any issues and I'll try another DCIN to see if anything changes.

 

[nik1981]

2informaticos Changing the DCIN didn't make any differences. Checked around U6900/01 under the microscope and it all looks perfect unfortunately.

Just to be clear. When PPBUS_G3H is below 11.84v (usually around 11-11.4v when just on battery) the magsafe light doesn't come on and the battery doesn't charge. But when PPBUS_G3H is 11.84v or above, the magsafe light does come on and the battery charges perfectly.

 

[2informaticos]

"Checked around U6900/01 under the microscope and it all looks perfect unfortunately."
I was expecting to get some voltages for U6900/01, when NO Magsafe light present...

PPBUS_G3H voltage varies, according with battery charge level; you can have 6V there, with empty battery.
Be sure =CHGR_ACOK is always high; CHGR_ACIN should also be high.
If not, change U7000.

 

[nik1981]

Sorry, thought I was just looking for damaged traces, liquid etc..

U6901 Pin 1/2 SMC_BC_ACOK = 0v, Pin 3 GND = 0.0v, Pin 4 SMC_BC_ACOK = 0.0v, Pin 5 PP3V42_G3H = 3.452v

I'll check voltages on U6900 now too

 

[JohnB8812]

PPBUS is 12.48 with just the charger? This makes me think maybe there is corrosion under the SMC. Remove edge bonding and give it a light reflow. See if it comes all the way up to 12.6 after that

 

[2informaticos]

"CHGR_ACIN should also be high."
???

 

[nik1981]

Ultrasonic clean and an SMC reflow did the trick. Tested for a couple of days without the problem returning. Thank you for the help