6500-CX Hearing Aid Test System - Frye Electronics

c. Interfaces between the 6500-CX and the remote module push button keys;
latches rapid key strokes for later reading by the 6500-CX CPU. U3D and U1C
form R-S flip flops. These flip flops are reset by the 6500-CX CPU after checking
for a key stroke. Transparent latch U3B is permanently wired as transparent.
It is used as a tri-state output buffer only. U3B couples the outputs of the
R-S flip flops to the CPU data bus.
d. Switches the 6500-CX prescaler input between the M1550E sound chamber
microphone and the remote module. (U2MB)
e. Controls the remote module REFERENCE MIC/PROBE MIC switch. (U2B)
f. Routes the signal from the Signal Generator Board to either the 6500-CX
Power Supply Board audio power amplifier (to sound chamber) or else to the
6500-CX Interface Board audio power amplifier U3F (to Quik-Probe speaker).
g. Provides audio power amplifier for the Quik-Probe speaker. U3J is stable with
gains greater than 10. Do not attempt to trouble shoot this circuit with gain
less than 10. U3J has internal short circuit protection and internal over temperature
protection. If the Quik-Probe speaker output is shorted, 6500-CX
Power Supply Board resistors R16 an R18 may produce smoke and may open.
Note: The Quik-Probe SPEAKER LEVEL setting is dependent on the rear panel
AUDIO SOURCE LEVEL setting.
4.8.1.1 Interface Board Connectors
J1 card edge 50 pins Lower system bus
J2 card edge 50 pins Upper system bus
J3 square pins 5 pins to 6500-CX digitizer board
J4 square pins 5 pins to 6500-CX rear panel, hand wired
misc
J5 IC socket 14 pins to 15 pin rear panel Remote Module
Connector
J6 square pins 5 pins to 6500-CX rear panel (M1550E)
Microphone Input
46 FONIX 6500-CX Maintenance Manual