User Guide

After Sales
Technical Documentation
THA–4S
Troubleshooting Guide
Page 7
Original, 12/95
Receiver Fault (1)
R230
A
B
Receiver
fault
N
NN
N
N
N
N
N
Y
N
N
N
N
N
N
N
N
Y
Y
Y
Y
Y
Y
Y
Y
Y
Y
N
Y
Y
Y
Y
Y
Simplex
sens TX (off)
OK
Noise or AF
signal at X101
pin 4 XEAR
Is VRX
(V221c) 4.85V
Is Vref
(N101/pin 2)
4.85V
Replace N101
TX spectrum
OK
is
Transmitter fault
Replace duplex
filter Z201
Check:
V221, V222, R295
R291, R292
AF signal at
C117
test point
2–4Vdc
J200 middle
channel
AF signal at
C222 (DAF)
Injection level
at N201/pin 1
–32dBm 86.4
Check:
V201, C207,
C208, C229,
C249
Earphone fault
Check:
C105, N100,
C116
Check RF
level at C249
–22dBm
968.25MHz
RF level C251
–25 dBm
14.4Mhz
Check:
G200,N202
Check:
R289, VRX=4.85V
Check:
R217, R216,R220,
V204
Check:
R218,R219,L206,
R290,L207,R222,
C239,
V204/c
4.75Vdc
V205/c
2.4Vdc
Check:
R222=0.9Vdc
Negative
voltage on
V206/A
Negative
voltage on
C244
Check:
R224, R223
Baseband
Check RF
level at N202 /6
–35dBm
968.25MHz
Check:
C253, R232, R238
N202
Check:
R225,L208
Check:
R221, R300, C259
C230
Channel 380 RX level –60dBm PROBE 10:1 10 Mohm/14pF
Injection level
at C208 –24dBm
968.25MHz
Y
N
MHz
Y