Asus b9440u power problem

[jasko_jacker]

ASUS B9440U no boardview no documentation, power AC comes from a small indipendent circuit
as shows in first pic, this circuit don't show any sign of current when it's attached at AC power adapter.
However the battery is in fully charge status but the system dont start.
So I think: first resolve a probably motherboard issue and then I try to solve the AC circuit issue.
Battery charger chip is BQ24780S that receive the signal shows in the pics but LODRV is 0 insted the voltage of the battery.
In the datasheet:
When the adapter is not present, ACDRV is pulled to CMSRC to keep ACFET and RBFET off.
BATDRV stays at VSRN + 6 V to connect battery to system if all the following conditions are valid:
• VVCC > UVLO
• VSRN > UVLO
• VACN < 200 mV above VSRN (ACN_SRN comparator)

ACDRV is >20 so the above conditions are met but LODRV remain off.

[Techtiger]

Re: Asus b9440u power problem

pin ACN & 2 ACP connected to CLR must be +19V ACDRV is not Active most Probably
2 Fets are N-Channel pin 5 6 7 voltage are 0V ?

[jasko_jacker]

Re: Asus b9440u power problem

I'm trying to obtain B+ with battery only.
All other BQ24780S -> 0 Volt in battery mode, I read from datasheet:
When the adapter is not present, ACDRV is pulled to CMSRC to keep ACFET and RBFET off and disconnecting
adapter from system.
CMSRC and ACDRV in absence of battery shoult be 0 (see pag 27 fig 16) to disconecct AC line from battery line , right ?
It's possible that the problem is battery voltage, because on battery I read 15.5 Volt but I have from it only 14.8 volt, it's sufficent to start BQ24780S ?
however both ILIM and BATDRV have the right voltages.
which signals must be present to operate the circuit in discharge mode ?