Motorola EP350 Service Manual page 121

UHF1 Troubleshooting Tables: Troubleshooting Table for Board and IC Signals (UHF1)
Table 12-4. Troubleshooting Table for Board and IC Signals (UHF1) (Continued)
IC Designator
(DTMF decoder)
FL701(VCTCXO)
Q206(N/S SW)
Q304
Q305
Q503
Q407
Q408
Pin Pin Function
2 IN-
3 GS
4 Vref
8 OSC1
10 VSS
11 TOE
17 STD
18 EST
19 ST/GT
20 VDD
1 VCON
2 GND
3 OSC out
4 VCC
E GND
B N/S SW
C Collector
E +5V
B To Q305 collector
C RX_B+
E GND
B RX_EN
C To Q304 base
E GND
B TX_EN1
C To Q706 base
E +5V
B To Q408 collector
C TXVB
E GND
B TX_EN2
C To Q407
DC Voltage (V) Comments (Condition)
1.6
1.6
1.6
1.6 3.579545 MHz input
0
3.3
High At DTMF detecting
3.3
3.3
3.3
1.9
0
osc Generate the 12.8 MHz
5
0
12.5 kHz: Low
12.5 kHz: High
25 kHz: Low
5 At RX Mode
Low
4.7
0 At RX Mode
High
Low
0 At TX Mode
High
Low
5 At TX Mode
Low
4.7
0 At TX Mode
High
Low
12-5