Checking The Back Light Unit - HP f1723 Service Manual

3. Checking the back light unit

Is +22.5V supplied to inverter PWB?
OK
Check the BKLT_EN signal of the rectangle input P301 pin 2 at TTL high level
OK
OK
1) Inverter cable disconnection.
2) Inverter of LCD module failure.
Page 16
Failure point
NG
1) Inverter cable disconnection.
2) Power board failure.
Is a "H" level being output in the TTL level from I304 pin 41
NG
Or, is BKLT_EN signal of the rectangle being output?
Printed wire broke between
I304 pin 41 and R387.
Check the PWM signal of the input from I304 pin 23 is a PWM signal.
NG
1) Printed wire broke between
I304 pin 23 and R301.
2) I304 failure.
Failure point
f1723 / FP7317 / L1702 / vf17 / FP17
NG
Failure point
Failure point