3M 478DA (D-15) Troubleshooting Manual page 12

Technician Troubleshooting Guide
Problem
No outbound audio:
Power Indicator Light
(green) is ON.
TALK Indicator Light
(red) is ON when TALK
SWITCH is pressed.
With car on loop, VEHICLE
Indicator Light (yellow) is
ON, but vehicle detection tone
does not sound.
With car on loop, VEHICLE
Indicator Light (yellow) is
OFF, and vehicle detection
tone does not sound.
Outbound audio distorted.

Food Services Trade Department
3M Center, Building 551-1E-02
St. Paul, MN 55144-1000
Possible Cause
Defective menu speaker,
menu mic, or wiring.
Defective analog board.
Vehicle Detect-to-Main
signal too low.
Defective analog board.
Defective logic or analog
board.
Defective analog board.
Defective internal
microphone.
Defective menu sign
speaker.
Printed on 50% recycled paper,
including 10% post-consumer waste.
Correction
Check and replace menu
speaker, menu mic, or wiring.
Check and replace analog
board.
Adjust R6 to increase signal
level.
Check and replace analog
board.
Check and replace logic or
analog board.
Check and replace analog
board.
Replace microphone.
Replace menu sign speaker.
Model 479 (D-30)
Printed in U.S.A.
© 3M 1997 January
78-6912-0637-5 Rev. A