820-00928 Shows Low Battery icon and Only Boots in SMC Bypass Mode

[peeka79]

Hi Guys,
I am working on a Customers 820-00928 board that will not power on and shows Low Battery icon. Machine Boots up in SMC Bypass Mode but does not see any battery? PPBUS_G3h is 13.02V With Battery Connected while running in SMC Bypass mode and PPBUS_G3h is 12.58V while machine is off and charger plugged in with battery connected. An original 87w Charger is being used and battery is Good. I tried the machine with a different 820-00928Board and Machine starts right up without Problems. All 4 USB_Chips are good and getting 20V on the AmpMeter...No Liquid Damage anywhere on Board. I’m also getting the following measurements...
PM_BATLOW_L. 3.3V
SMC_ONOFF_L 3.1V
PM_RSMRST_L 3.29V while Running and 0V before boot up
PM_PWRBTN_L 3.19v

Any Suggestion where to start looking? ANY help would be Greatly Appreciated...Thank You

 

[2informaticos]

An SMC sensir is triggered and stops the machine to start.
Check first resistance over C7020/23.
Also check SMC_DCIN/PBUS_VSENSE and SMC_DCIN/BMON_ISENSE levels.

 

[peeka79]

Hi 2informaticos, Thank You for the quick response and Help...Here are some measurements I took....

C7020 3.4 ohm
C7923 2.6 ohm

SMC_DCIN_VSENSE...Getting 2.6V
R5498= 31.5k pin 1 20V / Pin 2 2.6V
R5499=4.7k
C5498 = 4.7.4K

SMC_PPBUS_VSENSE... 0.00V
R5488=27.4K
R5489=5.5K
C5489=5.4K

Q5490
PIN 2...3.34V then drops to 0.0V

Q5480 Pin 2 ....3.3V then drops to 0V after a few seconds
Pin 3....12.58V Then drops to 0 after a few seconds
Pin 4....12.58V Constant
Pin 5....12.45 V Constant
Pin 6...12.33V Constant

let me know what you think, and Again THANK YOU for your help.

 

[2informaticos]

"Q5490
PIN 2...3.34V then drops to 0.0V"
Is good to know SMC_PBUS_VSENSE when pin 2 goes high.

"Q5480 Pin 2 ....3.3V then drops to 0V after a few seconds
Pin 3....12.58V Then drops to 0 after a few seconds"
You didn't mention such drop for SMC_DCIN_VSENSE, why?

"and SMC_DCIN/BMON_ISENSE levels"
???