Filter
Top Products
Theory of Operation
AM700 Audio Measurement Set Service Manual
3–3
There are two analog generators: High Resolution and High Bandwidth. Each
generator has two channels of output. The High Resolution generator output
channels are independent (output completely different signals on either channel).
The High Bandwidth Generator outputs the same signal on both channels.
There also two digital audio generators: AES/EBU and the DSP (digital signal
processor). Either of these generators may be used to produce the same signals
capable of being produced by the High Resolution analog generator. In addition,
the AES/EBU digital generator has the added signal of jittered sine which is used
to jitter modulate the digital signal to test for jitter immunity of a circuit or
device under test.
The Front Panel contains the touch screen circuitry, the front panel key pad
circuitry, and the sound circuitry. Inputs from the analog resistive touch screen
and the key pad are processed by the Front Panel mP, located on the Main/CPU
board. Communication between the Front Panel and the Front Panel mP is done
on a special 4-wire interface circuit.
The touch screen consists of two opposing transparent resistive layers made of
7 mil polyester coated with indium tin oxide. The two layers are joined together
around the perimeter, but they are kept apart by insulating spacers in the middle.
The two layers are laminated to a chemically strengthened glass backing panel
using a special optical adhesive. The touch screen may be activated by a press of
a finger tip or stylus.
Vertical, horizontal, and video circuitry to display the AM700 visual interface are
contained in the Picture Monitor. The 7-inch (diagonal) display is non-interlaced
raster scan, operating at 31.469 kHz horizontal deflection rate and 59.940 Hz
vertical deflection rate. The monochrome CRT uses P4 white phosphor.
The 1.4 Meg floppy disk is on the Front Panel mP bus. Waveforms, files, and
programming data may be uploaded and downloaded through the floppy disk
drive.
The power supply is an pre-regulator inverter switching supply composed of a
primary rectifier, a housekeeping supply, pre-regulator, the inverter switching
circuit, output rectifiers, 15 V regulators, an alarm sensing circuitry that monitors
for overvoltage, overcurrent, and over temperature conditions, and the alarm
logic circuitry that shuts down the inverter switching circuitry in the event of a
problem.
The mains AC voltage is rectified to provide the drive power to the pre-regulator
switching circuitry. A line voltage switch sets the supply to operate on a nominal
voltage of either 115 VAC or 230 VAC. On 230 V operation, the primary
Audio Generator
Front Panel
Picture Monitor
Floppy Disk Drive
Power Supply (A12)