Drv Board: Pre-Drv Transistor (Q1) Bias Adjustment - Furuno FS-1575 Service Manual

3. DRV Board: PRE-DRV transistor (Q1) BIAS adjustment (FS-2575, -5075)
Procedure)
1. Turn OFF the power supply, and then disconnect the [J1: TX OUT] connector from
the TX board.
2. Turn ON the power supply, and then press the PTT on the handset to put the system
into a TX state.
3. Make measurement of voltage between TP1 and TP2, and then make adjustment of
the "R77" so that the voltage will come to 75 mVDC. BIAS current is 150 mA.
J2
ATT
RF IN
R77
Q1 BIAS ADJ.
CONFIDENTIAL (internal use only)
This confidential document is used only by FURUNO authorized persons.
It is strictly prohibited to reproduce the document in whole or in part without prior written permission of FURUNO.
T1
Q1
R78
Q2, 3 BIAS ADJ.
TP1
R11/87
0.5
Fig. 5.7.15 DRV Board: Q1 BIAS Circuit
5-45
R77
TP1
TP2
Q2
T2
Q3
TP3 TP2
R21
0.22
15V
5.7 Board Adjustment
Q4, 5
15V