Watkins-Johnson Company WJ-8718-19/FE Instruction Manual page 104

WJ-8718-19/FE HF RECEIVER CIRCUIT DESCRIPTION
3.3.6.5 Sync Serial Input/Output, A6A5 (794255)
The Sync Serial I/O interfaces the microprocessor on A6A1 with external
remote control equipment via A6A4. This permits the remote equipment to direct the
receiver to perform frequency scans and stop when a signal exceeds threshold. Scan
signals (Slew/Seek) from the remote equipment is interfaced to the address/data bus
and then to the microprocessor.
3.3.6.6 Front Panel Switch/Encoder, MFP-A1 (796013-5)
The Front Panel Switch/Encoder interfaces all front panel functions with
the Microprocessor on A6A1 via the address/data bus. Two major subassemblies are
mounted on the Front Panel Switch/Encoder: The Front Panel Switchboard, MFPA1A1
and the Front Panel Encoder, MFPA1A2.
3.3.6.6.1 Front Panel Switchboard (MFPA1A1A2) (796057-5)
The Front Panel Switchboard contains switch matrices and all front panel
LED displays and indicators. A programmable interface transfers switch matrix
information to the Front Panel Encoder and decodes display information sent from the
Front Panel Encoder for display purposes.
3.3.6.6.2 Front Panel Encoder (MFPA1A1) (796056)
The Front Panel Encoder receives switch matrix information from the Front
Panel Switchboard, encodes it and transfers it to the microprocessor on A6A1 via the
address/data bus. Also, the Encoder receives display data from A6A1 via the
address/data bus, decodes to a format suitable for display and transfers it to the Front
Panel Switchboard for display.
3.3.7 POWER SUPPLY SECTION
See Figure 3-8 for the power supply block diagram. The receiver may be
operated from either 110 Vac, 120 Vac, 220 Vac or 240 Vac. This voltage feeds Filter
Assembly FL1 which contains the input voltage selector. It then passes through fuses
Fl and F2 and through the main power switch, SI. From the switch, current is routed
through the Voltage Selector and into Transformer Tl. The Transformer has a dual
primary and center-tapped secondaries and produces outputs of 34 and 16 Vac. The
34 Vac is rectified and filtered and sent to Main Chassis regulators Ul and U2 and to
U3 on Motherboard A5. Ul and U2 on the back of the chassis provide regulated
+15 Vdc and -15 Vdc, respectively. These two voltages are supplied to most
of the circuits in the receiver. The 16 Vac is rectified by two diodes located on the
rear panel and filtered to become the +10 V unregulated supply. The unregulated
10 Vdc, with its unregulated ground, connects to U3, a +5 Vdc regulator. U3 supplies
+5 Vdc to the Synthesizer and Digital Control Sections. The unregulated 10 Vdc also
connects through two +5 Vdc regulators on A5 and provide two separate +5 Vdc
voltages to the 1st and 3rd LO Synthesizers.
3-21