Ac Power Supply Circuit - Furuno FR-1505 MARK-3 Series Service Manual

Block Diagram Power
AC Power Supply Circuit (03P9228)
The power supply circuit consists of a main-inverter, a sub-inverter, and a protectors. A P.F
(Power Failure) signal of "Low or 0V" is generated when the main-inverter cannot work
normally. This signal is sent to the RP-17 and all data is stored before shutdown.
Main-inverter
When the power switch is pressed, +12V regulator, Q5 starts operating, and power is applied to
the input voltage detector and switching regulator control circuit.
The switching regulator is turned on with the input voltage of 85 V or more. The main-inverter
derives +/-12 V. The switching frequency is adjusted by VR1 to 22.5 kHz.
Sub-inverter
The sub-inverter derives +115 V for the CRT circuit from +/-12 V, output of main-inverter. +5 V
and +32 V for tuning control is generated by a regulator from +12 V.
Protector
The protector activates when the input voltage is higher than 135 to 150 V (for 110 V sets),
turning off relay K2. The rush current protector, Q11 controls the current which flows into
smoothing capacitors. The Q11 is bypassed when the transformer T1 outputs the voltage
designed. The protector in the power supply line for antenna motor trips when the current is 8 A
or more for more than 2.5 seconds. The TX-HV protector circuit is turned on when 8 A flows on
the +12 V line. The short circuit protector for +115 V is provided in the sub-inverter.
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