Sigtronics EAI Operating Instructions User Manual

Page 10

vehicles engine running. If radio reception and transmission
through the EAI unit is fine, for EAI-S4 or EAI-S6 units this com-
pletes the installation. Skip down to the “System Operation”
section on page 11. If everything is OK for EAI-D4 or EAI-D6
units skip down to the “Radio 2 Hook Up” section on page
11. If something does not work correctly, check the following
trouble shooting guide:

RADIO TROUBLESHOOTING GUIDE

NOTE: For dual radio units (EAI-D4 or EAI-D6) it is far easier to
troubleshoot with only one radio connected to the Sigtronics
at a time.

First determine if the trouble occurs with the vehicle engine
running.

Vehicle Engine Off:

1. Can’t hear radio in headset:

a) Turn up radio volume at the radio as normal. Make sure

however, you are not picking up the radio through the
headset mics by briefly turning down (counter-clock-
wise) the intercom VOLume control all the way.

b) Check violet wire (SPEAKER HI and LO) connections from

the EAI to the radio.

c) For EAI-D4 or EAI-D6 units, make sure that RADIO 1/

RADIO 2 switch is set to the radio you want to hear.

d) Some radios do not have sufficient speaker audio to be

heard on a standard EAI system. For such radios a minor
modification can be done to the Radio Adapter unit to
increase the level (by approximately 300%). Refer to
Figure 6 below. Using small piece of hook up wire and
a soldering iron, jumper across the pads as indicated on
the solder side of the Radio Adapter unit circuit board.
For EAI-S4 or EAI-S6 units jumper across the “A” pads. To
increase the audio for RADIO 1 of a EAI-D4 or EAI-D6
unit, also jumper across the “A” pads. To increase the
audio of RADIO 2 on a EAI-D4 or EAI-D6, jumper across
the “B” pads.

2. Can’t talk to dispatch (transmit) on radio through the head
set:

a) Check the connections between EAI Radio Adapter unit

and the radio. Both white wires (PTT HI and LO) and the
Brown and Black wires (MIC HI and LO).

b) Check the Radio Transmit Mic Level adjustment.

c) If the EAI is connected to a Midland radio a Sigtronics Mic

Level Amplifier might be required to boost the transmit
level. Contact your Sigtronics dealer for details.

d) For EAI-D4 or EAI-D6 units, make sure the RADIO 1/

RADIO 2 switch is set to the radio you want to transmit
on.

Vehicle Engine On:

1. Electrical noise (alternator whine) in headsets when receiv-

ing on radio, or

Dispatch reports that they hear electrical noise (alternator

whine) when transmitting from vehicle through the head-
sets.

First make sure that the problem is only related to the radio

hook up. Make sure that you did the “Electrical Noise Test”
for the intercom (without the radios connected) on page 8
and fixed any problems there before you go further. If OK
then:

Check all six radio interface wires between the EAI unit and

the radio - MIC HI, MIC LO, PTT HI, PTT LO, SPEAKER HI, and
LO. Make sure that you have the correct pin numbers for
the radio you are hooking to. Make sure that MIC LO and
SPEAKER LO are not physically tied to the same pin on the
radio; even if they are tied together inside the radio.

If the wiring is OK, then noise is coming from radio.

Possible bad radio wiring, (Check radio power and ground-

connections for loose or corroded connections) or

Excessive noise is generated directly by the vehicle’s electri-

cal / charging system – most commonly known as alterna-
tor whine. This is only present when the vehicle’s engine
is running and recognized by the fact that the pitch or
frequency of the whine changes directly with the change
in engine rpm.

The preferred way to solve this type of problem is to have

the vehicle’s electrical / charging system serviced. The most
common cause of this type of noise is bad diodes in the
vehicles alternator. Other possible causes are: bad vehicle
voltage regulator; bad alternator or battery cable con-
nections; missing or bad engine or alternator grounding
straps.

If servicing the vehicle’s charging system is impractical,

installing a good alternator whine power line filter in-line
with the radio power wire(s) will usually accomplish the
same thing. All radio power wires will have to be filtered.
Some radios have more than one wire that hooks to vehicle
power. Contact the radio manufacturer for a recommenda-
tion on the best filter for the particular radio. NOTE: This
solution should not be considered a permanent fix. Vehicle
charging system problems of this type will eventually
cause other equipment failure as well as shorten the life
of the vehicle’s batteries.

2. Dispatch says too much background noise or unclear or

weak transmissions.

a) Check to see if a radio hand mic on the vehicle is also

active or ‘live” when transmitting through the EAI unit.
Check this while not wearing a headset and by talking
directly into the radio hand mic and pressing either EAI
PTT switches. Do not press the PTT button on the hand
mic itself. If dispatch can hear you loud and clear, then

FIGURE 6