toshiba c855-139 no sign of life

[ahmetozay]

Hi folks, this toshiba c855-139 has 19v. But there is no 3v/5v exist. also there is no voltage at on/off switch. i send the picture where 19v drops to 0.9 volt. thanks

[ahmetozay]

Re: toshiba c855-139 no sign of life

here is the charging circuit voltages

[dj_ricoh]

Re: toshiba c855-139 no sign of life

start from there!
ACN needs to be 19v trace it back and see what is bad

[dycc]

Re: toshiba c855-139 no sign of life

short somewhere. with multimeter check the 0.9v output to ground(adapter unplugged) ; you must get low impedance

first check the two N mosfet (big and small one ) on picture for low impedance.

if no short a this point assume bq24725 might be bad (rarely according to my experience) or one of the components( transistor cap ic chip) supply by 19v on the board is bad

[ahmetozay]

Re: toshiba c855-139 no sign of life

short somewhere. with multimeter check the 0.9v output to ground(adapter unplugged) ; you must get low impedance

first check the two N mosfet (big and small one ) on picture for low impedance.

if no short a this point assume bq24725 might be bad (rarely according to my experience) or one of the components( transistor cap ic chip) supply by 19v on the board is bad

Thanks for your replies especially Dycc, i cehecked the impedance on big and small mosfets and it is 8 ohm on the small one so i changed it and everything works ok. thanks again