Comb Board: 05P0869 (Fs-5075) - Furuno FS-1575 Service Manual

5. COMB board: 05P0869 (FS-5075)

The COMB board has a built-in V-SWR detection circuit to output the "VR: UN BAL"
signal from #1 of the "J4".
The UN BAL signal level will increase when PA1 and PA2 input power becomes
imbalanced
• When 500W is outputted (normal):
• When [RF output] port is "Open":
• When [PA1] or [PA2] port is "Open":
Fig. 6.11.12 FS-5075 - COMB Board Block Diagram
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5mVDC
1.77VDC
2.95VDC
RF IN 1
RF IN 2
T3
COMB
6-83
6.11 Level Check
UN_BAL
CR1
T1, T2
R1
25 ohm
140W
RF OUT
T4