Pa Board-1 - Furuno FS-1575 Service Manual

7.2.3 PA Board-1

05P0867A: FS-5075
05P0867B: FS-2575
Basically, the PA board amplifier circuits of the FS-2575 and FS-5075 systems are the
same. The difference between the two PA boards is the type of PA input transformer.
The PA board consists of a single-stage push-pull amplifier circuit that is driven by a
42V power supply, V-SWR detection circuit, and bias circuit.
The power gain of the amplifier is 10dB or more. For example, when the PA board
inputs power of 25W, it will output power of 250W or more.
The FS-5075 system is supplied with TX output power of 500W by combining power
from the PA-1 and PA-2 boards through the COMB board.
05P0867A T1: 5T992
05P0867B T1: 5T923
RF IN
R1, 2
J2
R5, 6
U7
PA
TEMP
PA TEMP
4
PA ON
3
VC
6
IC
7
VR PA
8
CHK PA
5
5V
VC
PA HW VER
1
9, 10
R36
1
J1
IC
Fig. 7.2.9 FS-2575/FS-5075 PA Board Block Diagram
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.
MRF448
Q2
T1
A
Q3
U1, Q4, Q5, U6
Q3, CR4
5.6V
PA BIAS
PA ON
AVR
R51
A
BIAS ADJ.
A
U3
Isolation
U5
AMP
VC ADJ.
R47
TP1
U2
A
R39
Isolation
U4
AMP
R41
IC ADJ.
A
7-22
T2
T3, 4
T5
SWR DET
TP2
L1 L2
A
R45
R37, 38
0.01 x2
A
PA
FS-5075: 05P0867A
FS-2575: 05P0867B
7.2 Transmission Circuit
RF OUT
J3
CR2, 3
42V
1-3
0V
5-7
24V
4
J4
C47 - 50, 56, 57
A