Furuno FAX-30 Service Manual page 12

NET circuit
Net circuit is Ethernet 10Base-T interface circuit using TCP/IP protocol. U2 is a full feature
Physical Layer device with integrated PMD (Physical Medium Dependant) sublayers to support
10Base-T Ethernet protocol.
PWR circuit
Fig.4 shows the block diagram of power supply circuit. The power supply circuit employs a
floating type flyback switching regulator. Switching regulator controller U5 outputs a switching
signal of 190 kHz adjusted by R38. R51 adjusts +15 V line voltage.
Reverse connection
protecting diode
10.8 VDC to 31.2 VDC
Fig.3 Block Diagram of NET Circuit
Filter
Reference
Protector
voltage
Fig.4 Block Diagram of Power Supply Circuit
PULSE
TRANSFORMER
T1, T2
Flyback
Controller
SW
Feedback
4
Chapter 2 Circuit Description
NAVNET or PC
Rectifier
Poly switch
RT1
+15 V
+3.3 V
+5 V