Compaq MV7540 Service Manual page 19

Check if the voltage is
normal.
Check the components
between H-driving output
and base of Q403 as R422,
C413, Q402, T401
Check if the voltage of PLL1 at
pin9 of IC401 is normal.
NO
check the periphery components as
C437, C435, R411.
Section2
Check if the voltage at base of Q403 is 0v
Check if the voltage at pin29 of IC401 is 11.5V
YES
Check the voltage at pin26 of
IC401 is normal when
H-frequency is 31KHZ.
Check if the
voltage is 11V
2
Check I C
NO
Cut pin29 and check if
the voltage of circuit is
normal.
NO
Check the power supply of
11.5V and 80V circuit.
The voltage is
0V.
.
Cut pin26 and check
if the voltage is 11V
NO
YES
Check if the voltage at
pin6 of IC401 is 3.9V
NO
Check C409 or IC401
19
NO
YES
Replace IC401
The voltage is between 2V
and 4.5V.
Check C413, C415, R425,
D405, Q402, which breaks
Q403 if they are bad.
Check the circuit
producing
HP MV7540