KEPCO MBT Series - Manual (Page 121)

MBTSVC111609
4-15
optical encoders and providing digital signals for the front panel alphanumeric display. Digital
Control Board A3 contains the following circuits:
• Microprocessor (U6)
• EPROM Memory (32K x 8) containing proprietary software (U12)
• Non-volatile RAM (8K x 8) (U16)
• D/A and A/D Converters (U18, U17)
• Reference Voltage Circuit (+5V) (U23)
• Peripheral Circuit for controlling LCD and keypad (U27)
• Isolated two-wire Digital Control Bus circuit (U1)
Component locations for Digital Control Board A3 are shown in Figure 6-5. Connector A3P1
connects the A3 board to Mother Board A5. Header-connector A3J1 is split between three two-
wire cables: pins 5 and 6 carry +5V Isolated used by the Digital Control Bus Circuit, pins 3 and 4
carry the IEEE 1118 bus signals and interface the A3 board with the IEEE 1118 Input/Output
Ports (A6J2 and A6J3), and pins 1 and 2 provide IEEE 1118 bus signals to Interface Board A14
via "G" option selector switch A8S1 on Front Panel Board A8. Connector A3J5 provides the
interface for Front Panel Board A8. Jumpers A3J3 and A3J4 must be installed for normal opera-
tion of the A3 board.
Microswitch A3S1 (accessible via the top cover) is used to set the node address of the MBT
power supply (see PAR. 2.5.1). Five binary bits (A0 through A4) allow selection of addresses
between 1 and 31, with A0 the least significant bit. Moving the switch towards the right forces a
“1” on that line.
4.3.4 AUXILIARY SUPPLY BOARD A4 (See Schematic Diagram, Figure 6-22)
Auxiliary Supply Board A4 generates voltages used by other circuits of the MBT Series Power
Supply. This board is identical for all MBT models and options, and contains the following cir-
cuits:
• Auxiliary Line Transformer (T1)
• Rectifier and Filter Circuit for ±15V (CR1, C1, C2)
• Rectifier and Filter Circuit for Driver Supply (CR2, C3)
• Rectifier and Filter Circuit for Return Supply (CR4, C5)
• +5V Regulated Supply for Logic Circuits (CR3, C4, U1, C7)
• +5V Isolated Regulated Supply for BIT bus (IEEE 1118 bus) (CR5, C6, U2, C8)
This board is identical for all MBT Series Power Supplies, regardless of option. Auxiliary Supply
Board A4 is connected to Mother Board A5 via connector A4P1.
Figure 6-6 shows component locations for Auxiliary Supply Board A4. Connector A4J1 connects
+5V (isolated) via a twisted pair cable to Digital Control Board A3 (A3J1, pins 5 and 6).