Theory of Operation
3-- 6
TDS1000 and TDS2000 Series Digital Storage Oscilloscopes Service Manual
Power Supply
The main power supply module for the TDS1000- and TDS2000-series
oscilloscopes is a wide input range universal supply. It is capable of providing
about 17 W of power for the oscilloscope while allowing the input to run from
about +90 V to +264 V. Input frequency ranges from 47 Hz to 440 Hz, which
allows operation in virtually all countries in the world and in a number of
off-grid environments such as military power on aircraft.
The secondary supplies from the power supply and the approximate current
draws are listed in the table on page 6--35 with the associated connector pins on
J101.
For information on voltages used in the oscilloscope, refer to the Troubleshooting
section of this manual.
Display Module
The display module is a standard passive liquid crystal display (LCD). The
monochrome unit is patterned with 320 columns by 240 rows, and has the
associated drivers and backlight. The backlight is based on a 5 mA side light
fluorescent tube.
The color unit is patterned with 320 columns x 3 sub-columns by 240 rows and
has associated drivers and backlight. The backlight is based upon a 5 mA top
light fluorescent tube which runs a higher voltage and is longer to provide
sufficient extra light to overcome the higher loss associated with the color filters.
Front Panel
You can access all of the switches, position encoders, and LEDs on the front-pan-
el board of two-channel oscilloscopes. Additionally, an IC on the front-panel
board provides buffering and multiplexing of switch signals to the main board.
Two signals and a sense line are provided by the main board to support the front
panel. One of these lines resets the scan; a second clocks the scan to the next
position; and the sense line receives the current state of the selected switch or
encoder position.
For the encoders, some amount of debouncing occurs inside the front-panel IC.
All key debouncing is handled in the display ASIC on the main board.
Two-Channel
Oscilloscopes
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