LG HT904TA Service Manual page 18

C
YES
Laser
turns on when
reading disc?
YES
Put disc in?
YES
Disc ID is correct?
YES
Does spindle rotate?
YES
D
DVDLD or
NO
CDLD output
property?
YES
Collector
voltage of power transistor
is OK?(Q403, Q405)
YES
Check cable connection
between transistor output and
pick-up head.
NO
Laser off.
Proper
NO
RF signal on
MT1389MH.
YES
Check the RF connection
between AM5890 and MT1389MH.
Proper
NO
SPINDLE signal on
MT1389MH.
YES
SPNP
& SPNN output
properly?
YES
Check the cable connection
between spindle and main
PCB.
2-
Check the laser power circuit
NO
on MT1389MH and
connecting to power
transistor.(Q403, Q405)
NO
Check the related circuit on
laser power transistor.
NO
Check the related circuit on
MT1389MH RF signal.
NO
Check the SPINDLE related
circuit on MT1389MH.
NO
Check the spindle control amp
circuit of motor driver.