LG KG70c Service Manual page 30

KG70C
3.2.2 Check VCTCXO Circuit 3.2.2 Check VCTCXO Circuit
Test Point Test Point
Pin#3 Pin#3
Pin#4 Pin#4
Circuit Diagram Circuit Diagram
Waveform Waveform
Graph 3-2-1(a) Graph 3-2-1(a)
U101 U101
Figure 3-2-2 Figure 3-2-2
Checking Flow Checking Flow
Check U101 Pin#3 Check U101 Pin#3
◆ Refer to Graph 3-2-1(a) ◆ Refer to Graph 3-2-1(a)
19.2MHz OK? 19.2MHz OK?
Check U101 Pin# 4 Check U101 Pin# 4
◆ Refer to Graph 3-2-1(b) ◆ Refer to Graph 3-2-1(b)
+2.9V_TCXO OK? +2.9V_TCXO OK?
Check U401 Check U401
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VCTCXO Circuit is Ok VCTCXO Circuit is Ok
Yes Yes
See next Page to check See next Page to check
Duplexer Duplexer
No No
Yes Yes
Changing U101 Changing U101
No No
Graph 3-2-1(b) Graph 3-2-1(b)