Pa Board: Driv Transistor Q2-Q3 Bias Adjustment (Fs-1575); Pa Board: Pre-Driv Transistor Q1 Bias Adjustment (Fs-1575) - Furuno FS-1575 Service Manual

4. PA Board: DRIV transistor Q2-Q3 BIAS adjustment (FS-1575)

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 adjustment of the "R81" DRIV BIAS adjusting variable resistor so that
voltage between TP3 and TP4 will come to "40 mVDC."
BIAS current: 40 mV/0.1Ω = 400 mA
J2
ATT
RF IN
R80
Q1 BIAS ADJ.
15V
Fig. 5.7.9 FS-1575 PA Board (05P0868): Q2-Q3 BIAS Circuit Block Diagram

5. PA Board: PRE-DRIV transistor Q1 BIAS adjustment (FS-1575)

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 adjustment of the "R80" PRE-DRIV BIAS adjusting variable resistor so that
voltage between TP1 and TP2 will come to "75 mVDC."
BIAS current: 75 mV/0.5 Ω = 150 mA
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.
Q2
T1
Q1
TP1
Q3
R81
Q2, 3 BIAS ADJ.
TP2 TP4
R11/87
0.5
R23
0.1
5-39
Q4
T2
Q5
R79
PA BIAS ADJ.
TP3
5.7 Board Adjustment
T4
24V