Sigtronics SCI-S6 Installation Instructions - Manual (Page 5)

To upgrade, first remove the SPA unit from the aircraft panel. This
is done by unscrewing the two Phillips head screws and the nut on
the ON/OFF switch. Remove the printed SPA panel. Pull the SPA
unit out and unplug the white connector from the wiring harness.
Next, drill the center hole in the aircraft panel out to 7/16”. Then drill
the two outer holes to 9/16”, then use template to mark the position
of the final two holes and drill. Finally mount the SCI-S chassis
(see Figure 2):
1. Remove the knobs from the Volume and Squelch controls using
a 0.050” Allen wrench. NOTE: DO NOT REMOVE the nuts from
the Volume/Squelch (VOL/ SQ) or ALL/ISO/CREW controls.
2. Insert the SCI-S unit from the rear of the aircraft panel with the
appropriate arrow on the unit chassis pointing upwards. The
squelch indicator lights (LED’s) should easily fit through their
respective holes.
3. Install the printed SCI-S panel and lightly thread the two 4-40
screws through the holes in intercom panel. The nuts on the
Volume/Squelch and ALL/ISO/CREW controls should fit inside
the aircraft panel holes.
4. Tighten the two screws. Make sure LED’s have unrestricted
movement in aircraft panel holes.
5. Put the knobs on the Volume and Squelch control shafts and
tighten the Allen screws.
Wiring Change
The wiring changes to an existing SPA installation are as follows.
Re-wire the pilot, co-pilot, and passenger(s) headphone lines. You
will not need the 4-foot Intercom/Aircraft interface cable (12 or 15
pin) that comes with the SCI-S system. You will use the SPA har-
ness already in the aircraft and the 4-foot Headphone/Music inter-
face cable (12 pin).
In a SPA installation, the tip terminals of the pilot, co-pilot, and pas-
senger headphone jacks are wired to the blue wire (pin 3). They
need to be disconnected from there, the mono headphone jacks
need to be replaced with the supplied stereo headphone jacks
and connected to their respective pins on the Headphone/Music
interface harness. (See Figure 4 on page 3) Make sure that the
blue wire (pin 3) is still connected to the tip of the radio headphone
line.
INSTALLATION CHECK-OUT AND ADJUSTMENTS
After the unit is installed, again check that the SCI-S unit chassis,
jacks, and wiring harness are clear of all aircraft operating controls
and cause no interference with them. Next, to check out the SCI-S
unit installation plug in all the headset mic and phone plugs into the
respective intercom jacks. Put on the pilot’s headset and position
the boom mic close to the mouth, as is the practice with a hand-
held mic. Voice clarity is best when the mic is at one side of the
mouth and 1/4” from the lips.
To assure that the aircraft radios, pilot’s headset, and PTT switch
are connected and functioning properly, remove power to the SCI-
S by pulling intercom circuit breaker. If applicable, set the aircraft
audio panel to “Headphone” position. Then turn on the aircraft
radio(s) as usual, and verify that the pilot can hear the radios and
can transmit using his push-to-transmit switch and headset. Aircraft
radio(s) and audio panel should operate exactly as they did before
the SCI-S system was installed. Aircraft radio reception should not
be heard in the co-pilot or passenger headsets. There should be
no intercom between headsets without power applied to the SCI-S
unit.
Next restore power to the SCI-S unit. Switch ALL/ISO/CREW
control to the “ALL” position. Set the SCI-S volume controls to
mid-position. Set both SCI-S squelch controls fully clockwise. Pilot
can operate the aircraft radio(s). In this mode all headsets on the
intercom will hear the aircraft radio(s).
It may be necessary at this time to adjust the SCI-S unit mic output
to the aircraft radios. A small adjustable potentiometer is provided
inside the unit for this purpose. It is accessible through a hole in
the side of the SCI-S chassis. It is marked “Mod. Adj.”, and can be
adjusted with a small blade screwdriver. In the event of over-modu-
lation (garbled) or reports of weak transmissions over the aircraft
radio, an appropriate adjustment can be made. Clockwise rotation
increases the output level to the aircraft radio mic input. Counter-
clockwise rotation decreases modulation level. This adjustment
sometimes needs to be made after the initial installation of the
intercom or if a new radio is installed. (The output is set for unity
gain at Sigtronics).
It may also be necessary to adjust the SCI-S unit radio receive
input from the aircraft radio. A small adjustable potentiometer is
provided inside the unit for this purpose. It is accessible through a
hole in the side of the SCI-S chassis. It is marked “RX Adj.”, and
can be adjusted with a small blade screwdriver. In the event of low
aircraft radio volume in the “ALL” or “CREW” mode relative to “ISO”
mode, an appropriate adjustment can be made. Clockwise rotation
increases the input level to the SCI-S radio receive input. Counter-
clockwise rotation decreases input level. This adjustment some-
times needs to be made after the initial installation of the intercom
or if a new radio is installed that has a low output impedance or low
output power. The adjustment is best made with the pilot and co-
pilot headsets plugged in. (The input is set full CCW which is unity
gain for 500Ω radios).
You are now ready to check for proper wiring of the music sources.
First, make sure both squelch lights are off and intercom is in ALL
mode. Turn on the crew music source and listen for music through
pilot and co-pilot headsets. There should be music. Then switch to
CREW mode. There should also be music in both pilots’ headsets.
Similarly, turn on the passenger music source. There should be
music in the passenger headsets.
If everything checks out, refer to the MODE SELECTION and
AUDIO PRIORITY TABLES below as well as the separate SCI-S4/
SCI-S6 OPERATING INSTRUCTIONS sheet for proper use and
other operating modes of the Sigtronics SCI-S intercom system.
If something does not work as described, carefully go over the in-
tercom wiring again. If something is still not right or you have any
questions regarding the installation and operation of the Sigtronics
SCI-S intercom or any other Sigtronics product feel free to contact
us directly or email us at [email protected]. Technicians are
available Monday though Friday 8 am to 4:30 PM Pacific time.
This concludes the installation check-out.
SCI-S4/SCI-S6 MODE SELECTION TABLE
MODE PILOT HEARS CO-PILOT HEARS PASSENGERS HEAR
ALL
ATC, Crew ICS, Pass ICS,
Crew Music
ATC, Crew ICS, Pass ICS,
Crew Music
ATC, Crew ICS, Pass ICS,
Pass Music
ISO ATC
Co-pilot ICS, Pass ICS,
Crew Music
Co-pilot ICS, Pass ICS,
Pass Music
CREW
ATC, Crew ICS,
Crew Music
ATC, Crew ICS,
Crew Music
Pass ICS,
Pass Music
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