340 Chapter6
General Troubleshooting
Block Diagram Description
Display/Power Supply Section
A6 Power Supply
The A6 power supply is a switching supply operating at 40 kHz for low
voltages in both EC-series and E-series instruments.
In E-series instruments, the power supply also provides the 30 kHz
signal for the CRT supplies (cathode, filament, +110 Vdc, and post
accelerator). The A6A1 high voltage module contains the high-voltage
transformer and post-accelerator multiplier. Power is distributed
through W8 to A17 and through W1 to the rest of the assemblies.
A6A1W2 supplies CRT cathode and filament voltages to the A17
assembly.
The speed of the spectrum analyzer fan is variable. A thermistor on A6
senses the temperature and adjusts the fan speed accordingly. This
allows the spectrum analyzer to run quietly in most room-temperature
environments and faster (louder) only when necessary.
A17 LCD Display Driver (EC-series)
The display is an LCD color flat panel screen with 640 X 480 VGA
resolution. A connector for an external VGA is available at the rear
panel. The A17A1 backlight supply provides the high voltage to supply
the two backlights in the LCD display. The LCD display is not
adjustable.
The display driver board consists of the Hitatchi 7707 processor, an
Actel FPGA, DRAM, SRAM, a filter circuit, and a video DAC. This
board monitors the 8560 EC-series controller board, copies display
instructions to local memory, creates a bitmap from the data, and
generates the signals needed to drive the LCD and a VGA monitor. The
video DAC converts the digital color information from the LCD to
analog; these analog signals drive the RGB color lines on the VGA port
on the rear panel.
A17 CRT Display Driver (E-series)
The line generators on the A2 assembly drive the A17 CRT driver. The
A17 assembly contains X and Y deflection amplifiers, focus and
intensity grid amplifiers, and miscellaneous CRT bias circuitry. The
high voltage is supplied by A6A1 high voltage module.
In fast-analog zero-span mode (sweep times ≤30 ms without Option
007), the 0-SPAN VIDEO signal from A3 and the sweep ramp from A14
connects to the A17 CRT driver. The graticule and annotation are still
digitally drawn.
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