AMX TXC16 Plus Specifications download pdf (Page 190)

SG-2000 MANUAL 183

The SGC Building, 13737 S.E. 26th St. Bellevue, WA. 98005 USA

23.3 DISPLAY SECTION TESTING PROCEDURES

This section describes the testing procedures for the Display section of the SG-

2000 radio.

23.3.1 Required Testing Equipment

HP 331A Distortion Analyzer

HEATH KIT IG-5218 Audio Signal Generator or equivalent

PS-30 13.6V power supply

SGC Display RX Audio Test Fixture

Power Supply Capable of at least 2 Amps at 13.6 Volts for connecting the SG-

2000 to the PS-30 power supply

Connection Cables; CPU extension cable

Keyboard extension cable

DMM

SG-2000 Test Head

SG-2000 without head, RF Out adjusted to minimum, bypassed AM filter.

SG-2000 Test Head Microprocessor With Display Test Chip (IC16)

SG-2000 Test Head Microprocessor With Normal Chip (IC16)

SG-2000 Sample Display Boards ( 1 working and 1 bare PCB, latest rev)

Oscilloscope

Microphone PTT Toggle Switch

Microphones; 1 carbon, 1 dynamic

23.3.2 Circuit Description

The display board provides the keypad board interface, volume control, micro-

phone amplifier, display interface, and back light control. The circuit can be seen

on schematic J30100910. Information is received from the key board matrix on

connector J3 and is passed to the head processor board on connector J2. The one

exception to this is the on/off switch; it is passed from connector J3 to the exciter

in connector J1.

The line receiver takes the balanced audio signal coming from the exciter and

converts it into an unbalanced signal for the volume control. Volume control is

provided by using a digital to analog (D to A) converter, IC16. In addition, the

received audio signal is rectified by IC12B and fed to the analog to digital (A to

D) converter, IC14. IC14 also converts the photo cell voltage (on Rev E boards

and earlier) and sends output to the head processor via pin 12 on J2. Jumper J6 is

used to select either a dynamic (factory setting) or carbon microphone. The

audio signal is converted from an unbalanced signal to a balanced signal by the

line driver, IC11A and B. The balanced audio signal is sent to the exciter through

J1. When in CW mode, the CW signal is received from the exciter and treated as

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AMX TXC16 Plus Specifications Page 190