Theory of Operation
3-- 6
TDS1000B and TDS2000B Series Oscilloscope Service Manual
Power Supply
The main power supply module for the TDS1000B and TDS2000B series
oscilloscopes is a wide input range universal supply. It is capable of providing
about 25 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 power on military aircraft.
The secondary supplies from the power supply and the approximate current
draws are listed in the table on page 6--25 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 color unit is patterned with 320 columns x
3 sub-columns by 240 rows and has the associated drivers and backlight. In both
displays, the backlight tube is in a 5mA top lamp configuration.
Front Panel
You can manipulate all of the switches, and position encoders on the front-panel
board of two-channel oscilloscopes. Several LEDs are used to indicate when the
Multipurpose knob is active, when Autorange is active, and when a Save action
is in progress. For more information on the LEDs, refer to the User Manual for
your oscilloscope.
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.
The LEDs are controlled by latching the value of the Channel 1--2 front panel
scan counter when the appropriate scan value is set.
Two-Channel
Oscilloscopes
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