Dsc; Wr1 - Furuno FS-1575 Service Manual

1. RX
The output frequency of the 1st Local signal in J2B mode is "Fc + 53.964 MHz."
When conducting a DAILY TEST, Fc is set to "0 MHz " to output a frequency of
"0 MHz + (53.964 MHz + 85 Hz)." Consequently, since the output frequency of the 2nd
Local signal is 54 MHz, the 2nd IF (IF RX) signal is given as "36 kHz + 85 Hz."
These two signals, i.e., mark tone signal and space tone signal, are inputted in the
T-CPU board. The receiver is determined to be OK when both tone signals can be
detected by the RX test. The signals are checked at a level of approximately 60 dBuV in
antenna input equivalent.
Note) The above means that the test on the 1st IF signal is conducted with the 1st
Local signal leakage. Consequently, a circuit from the RX board antenna
input to the 1st MIX is not checked.
RX
ANT RX
Q2
CR1 CR3
30MHz
ATT
0MHz + (53.964MHz + 85Hz)

2. DSC

This test menu is used to check for communications between the DSP (digital signal
processor) and the MAIN CPU. DSC test is determined to be OK when data from the
DSP is detected in the MAIN CPU.

3. WR1

The output frequency of the 1st Local signal is "Fc + 35.964 MHz."
When conducting a daily test, Fc is set to "0 MHz" to output a frequency of "0 MHz +
(35.964 MHz + 85 Hz)." Consequently, since the output frequency of the 2nd Local
signal is 36 MHz, the 2nd IF (IF RX) signal is given as "36 kHz + 85 Hz."
These two signals, i.e., mark tone signal and space tone signal, are inputted in the
T-CPU board. The WR1 watch receiver is determined to be OK when both tone signals
can be detected by the WR1 test. The signals are checked at a level of approximately
60 dBuV in antenna input equivalent.
Note)
The above means that the tests on the 1st IF signal are conducted with the 1st
LOCAL signal leakage. Consequently, a circuit from the WR1 board antenna RF
circuit to the 1st MIX circuit is not checked.
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.
FL1
U7 U6
Q6 Q1
53.964MHz
IF AGC
54MHz
Fig. 6.1.1 RX Test Circuit Diagram
6-3
6.1 [MENU] -> TEST
T-CPU
U8
IF RX H
U8
36kHz
IF RX C