sony cs290
mbx-196
shortly on and off
flash bios
change i/o chip
3.3v ok
5v ok
19v ok

See SC on inductors, other voltages. Reconnect RTC-battery.

reconnect rtc bat
all inductor not sc to GND,...but PL12 in VCCP have 28 ohm by gnd
capacitor on N-BRIDGE have 28 ohm ...is this normal?
check voltage in power on time(2sec)
checked voltage on inductors and GND
1.5v ok
1.8 v ok(ram)
3.3v ok
5v ok
!!not have any voltage on cpu power (2 inductor enclose cpu)

Is 0.9V on pin 2 of PU3 (or on capacitors on RAM modude)?
Is 1.8V on both sides on PQ37 ?
Is voltage on PL12 and what is value?
Is VCC 1.1 on pins 123 of PQ44, PQ45 ?
is a 3.3V enable signal on pin 29 (VR_On) of PU9?
is a 3.3V enable signal on pin 44 (VR_On) of PU1?
What on pins 48,20,22 of PU1?

Also you need to check PowerGood signal for all IC, where it used. (see schematic diagram)

i download schematics and find part and test voltage as soon as
but i have problem by ISL6262A that under a mini pcb of input voltage
are you have way to test voltage on this pwm ic?

upload foto please

i am sory....ISL6262A (i write ics6262) PU1

You need to solder wires

test reslt:
1.8v on cap of ram
PL12=1.05v

PU9(ISL6263):
pin29 of pu9 =3.3v
pin31 of pu9=0v

PU1(ISL6262 CPU CORE):
pin44=0v
pin48=3.3v
pin20=19v
pin22=5v

Also consider southbrige is defective and north<->south bridge might not work properly.