Furuno FM-8800, Service Manual

Page: 157 / 268

5.4 Block Description
5-25
5.4.6 PWR (05P0776)
This outputs the voltage of +15 VDC from +24 VDC input power. Each protection
circuit and their functions are as below.
Fig. 5.4.21 PWR Block Diagram
OVER VOLTAGE PROTECTION
This protection functions to stop the output when power input is anywhere b42
to +43 VDC and also functions as an automatic recovery function. This detects voltage
on CR4 and controls power relay: K1 through Q 2 and Q3.
LOW VOLTAGE PROTECTION
This protection functions to stop the power output when the power input is anywhere
b14 to +15 VDC. Detected voltage is determined by voltage divider(between R
7/9 and R 8) and its voltage is used to control U2. Normally, 300 ms after turning on the
power, level will be “L” and sets U1 to “ON”.
RUSH CURRENT PROTESTION
When you turn on the power, K1 will be set to “ON” and then, RC (Remote Control) on
U1 will be set to “ON”. Delay of RC terminal will depend on C23 on U2.
Approximately 300 ms after turning on the power, level will change to “L”. If you turn
on the power without proper adjustment with RC terminal (RC=L level), rush current
will be discharged into U1 and might burn where K1 is connected. This protection
prevents rush current at the time of inserting RC power by adjusting RC terminal to “L”
level 300 ms after turning on the power.
PWR
05P0776
L1
L3 L4
L2
C1-7
CR1
CR4
02CZ39
C8-10
C11,12
C14,15
J1-#1-3
J1-#6-8
J1-#4
J1-#5
TB1
TB2
FG
AVR
(+12V)
AVR
(+12V)
Voltage
DET.
Q1: 2SD1271A
CR2: 02CZ12Y
U2: M51958BFP
U1: CBS2002415
+IN
-IN
+Vout
-Vout
RC
POWER SW
R3
R5
C23
R8
R7,9
Q2
K1
Q3
+15V
24VDC(+)
24VDC(-)
0V
PWR SW P
PWR SW M