Directv Tp- Demux /Modem Circuit - LG LSS-3200A Service Manual

8. DIRECTV TP- Demux /Modem CIRCUIT

2. If modem IC does not operate normally
START
YES
The IC 3.3V power is supplied
normally?
YES
The clock #5 operates normally?
YES
The clock #6 operates normally?
YES
The UART pin control operates?
YES
The IC902 power is supplied
normally with connecting phone line?
YES
The modem part soldering is OK?
YES
END
NO
Check IC901(4) voltage : 3.3V
NO
Check IC901(2) clock waveform
: See FIG. 05
NO
Check IC901(3) clock waveform
: See FIG. 06
NO
Check IC901(5) voltage : 3.3V
Check IC901(6) voltage : 3.3V
NO
Check the voltage between IC902(9)
and IC902(3) : about 3.6V range
NO
Check the voltage between JA901(3)
and JA901(4)with connecting phone
line : about +/- 48V
Check IC901(13) voltage with connect-
ing phone line : about 4.6V range
3-39