Tektronix TDS 620A, Service Manual

Page: 70 / 288

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All information (waveforms, text, graticules, and pictographs) is displayed by
the A30/31/32 Display system. The A30 generates the high voltages necesĆ
sary to drive the display tube. It also contains the video amplifier, horizontal
oscillator, and the vertical and horizontal yoke driver circuitry.
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The processor system sends instructions to and receives information from
the Front Panel Processor on the A12 Front Panel board. The Front Panel
Processor reads the frontĆpanel switches and potentiometers. Any changes
in their settings are reported to the processor system. The Front Panel
Processor also turns the LEDs on and off and generates the bell signal.
FrontĆpanel menu switches are also read by the Front Panel Processor. The
processor sends any changes in menu selections to the processor system.
The switch is one of the menu switches. However, it is not read by
the Front Panel Processor, but passes through the A12 Front Panel board
and the A11 DRAM Processor/Display board to the low voltage power supĆ
ply.
The front panel also generates the probe compensation signals
and .
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The connector provides access to stored waveforms, and allows
external control of the oscilloscope.
You can make hardcopies on the GPIB, RSĆ232 and Centronics ports.
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The low voltage power supply is a switching power converter with active
power factor control. It supplies power to all of the circuitry in the oscilloĆ
scope.
The principal switch, located on the rear panel, controls all power
to the oscilloscope including the Low Voltage Power Supply. The
switch, located on the front panel, also controls all of the power to the oscilĆ
loscope except for part of the circuitry in the Low Voltage Power Supply.
The power supply sends a power fail (~PF) warning to the processor sysĆ
tem if the power is going down.
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The fan provides forced air cooling for the oscilloscope. It connects to +25ĂV
from the Low Voltage Power Supply by way of the A11 DRAM Processor/DisĆ
play module.