Giga-tronics GT 9000, Руководство по эксплуатации и техническому обслуживанию

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3.3.21 Data Entry — PC Assembly A106
This board holds the pushbuttons for the main power, numerical keypad, modulation buttons and
the sweep marker buttons, as well as any corresponding LEDs. In addition the Intelligent HP
alpha numeric displays reside on this board.
As on the Pushbutton Board A105, the pushbuttons are read and the LEDs are lit using the rows
and columns scheme. The four 8-digit Intelligent HP alpha numeric displays (DS1 thru DS4)
receive address and data information from the display driver board.
When the unit has power applied to it, the standby LED DS13 is lit by the 20 V from the power
supply via P2. When the power switch is activated the 20 V coming in on P2 is switched to
energize the power relay switch which supplies power to the rest of the unit.
3.3.22 Main Tune — PC Assembly A107
The Main Tune assembly is mounted on the chassis between the microwave deck and the power
supply capacitors. The board holds the transistors which provide the current drive to the Main
Tune coils of each of the YIG oscillators. These transistors must provide high currents with
substantial power dissipation, which requires the transistors to have a heat sink. The diodes at
the base of each transistor prevent the voltage from going too far negative.
3.3.23 Detector Buffer — PC Assembly A200
The Detector Buffer module is an important part of the leveling system. The 2.5 MHz Reference
signal is received from the level board (A10) at J7. This signal is detected by a detector at J6
and a DC voltage proportional to the power level of the reference signal is returned. L1, L2,
C15 and C16 filter the reference signal from the DC voltage returned from the detector, which
is then amplified by U5 and returned to the leveling board thru J5.
The detector inputs for leveling the output signal are at J4, J3, J2, which are for an external
detector (external ALC mode), the <2 band detector and >2 band detector respectively. The
appropriate detector is selected by its respective logic line which switches one of three
comparators (U4 A, C and D) which in turn switches on one FET (Q2, Q4 or Q5). The active
FET feeds the proper detector signal to the amplifier consisting of U3, U2 and U1. The output
is then fed back to the leveling board (A10). The remaining logic signal at P4 serves two
purposes: (1) When it is low it turns on the FET Q1 which allows the full voltage of the
External Detector signal to be applied to Q2. When the logic is high the External Detector
voltage is divided down by a factor of 10. (2) switches in a capacitor (when the logic is low) in
the <2 path to filter out the RF signal which is coming in on the detector voltage. This logic
signal remains low from 10 MHz to 50 MHz and then above 50 MHz it goes high which
switches the capacitor out of the <2 detector path.
Model GT 9000 Microwave Synthesizer
3-34
Manual No. 120AM00250, Rev C, September 1998