Directv Front- End Circuit(Qpsk) - LG LSS-3200A Service Manual

3. DIRECTV Front- End CIRCUIT(QPSK)

Start
YES
Power is supplied normally?
YES
IIC is operated normally? (SCL(TU360
(28)), SDL(TU360(27)) Pin -> HIGH)
YES
The signal of controlling Multi- Switch
is operated normally?
(using Oscilloscope and signal
strength on Menu)
YES
The signal from satellite is detected?
(using the split including DC block
port and Spectrum Analyzer)
YES
Tuner's error flag(TU360(15)) is
operated normally?
(using Oscilloscope)
High : Error, Low : normal
YES
Check QPSK- signals(P360).
DATA( Fig. 03 ) : pin 1,3,5,7,9,11,13,15
packet clock( Fig. 04 ) : pin 8
Byte clock( Fig. 05 ): pin 4
YES
End
NO
Check the power line referring the
circuit diagram.
NO
Check the connection between tuner (TU360)
and IIC line/ power/ peripheral parts.
Check the operation of LNBP20PD
NO
(IC360). Check the connection
between LNBP20PD and power line/
peripheral parts.
NO
Check the dish pointing.
NO
Check the state of satellite signal.
NO
Check the status of connection on
PCB.
3-16
(A)