Sigtronics SPA-4SN Installation Instructions - Manual (Page 2)

SHOULDER
WASHER
FLAT
INSULATED
WASHER
FLAT
METAL
WASHER
NUT
AIRCRAFT
PANEL RING
BARREL
TIP
INTERCOM
PANEL
4–40 SCRE WS
SWITCH
NUT
INTERCOM
DO NOT REMOVE
THESE NUTS
KNOB
KNOB
AIRCRAFT
PANEL
Figure 5
TIP
(RIGHT)
RING
(LEFT)
BARREL
(COMMON)
AIRCRAFT PANEL
NUT
Figure 2
Microphone Jack Figure 3
RIGHT
LEFT
STEREO
+
-
+
-
+ -
+ -
R C
R
C
C – 220 MFD, 25 VOLT CAPACITOR
R – 100 OHM, 5 WATT RESISTOR
NO CONNECTION
J2 (6) WHITE / VIOLET
J2 (4) WHITE / BROWN
J2 (5) BLACK
To SPA-4S
Figure 6
page 2
MOUNTING CHASSIS (See Figure 2)
1. Remove the knobs from the Volume and Squelch controls using a 0.050”
Allen wrench. Remove the nut from the ON/OFF switch. NOTE: DO NOT
REMOVE the nuts from the Volume and Squelch controls.
2. Insert the SPA-4S unit from the rear of the aircraft panel with the
appropriate arrow on the unit chassis pointing upwards.
3. Install the printed SPA-4S panel and lightly thread the two 4-40 screws
through the holes in intercom panel. The nuts on the Volume and Squelch
controls will fit inside the 3/8” diameter holes.
4. Tighten the two screws and switch nut.
5. Install the knobs on the Volume (VOL) and Squelch (SQ) control shafts and
tighten the Allen screws.
MOUNTING HEADPHONE AND MICROPHONE JACKS (See Figure 3)
1. Locate the mounting areas. (One mic and one headphone jack required
for each headset). Again, make sure that the jacks will not interfere with
any aircraft control components. (Note that the jack contacts will expand
when a plug is inserted into the jack and must have clearance to prevent
shorting.)
2. Drill 3/8” diameter holes for headphone jacks and install.
3. Drill 1/2” diameter holes for the mic jacks and install with the insulating
washers supplied. (See Figure 3).
Note: If the aircraft already has pilot headset jacks, the location can be used
for intercom with the following changes. The mic jack must be re-wired as
follows:
1. Remove any existing wires from the tip, ring, and barrel connections.
2. Connect the intercom white/black wire to the ring terminal.
3. Connect one end of a ground wire to the barrel terminal of the mic jack
and connect the other end to Intercom Central ground Point “A”.
4. Install insulating washers as necessary if the barrel of the mic jack is
mounted in metal. For the headphone jack, replace the mono headphone
jack with the stereo headphone jack. Connect the green wire (P2 pin 1) to
the tip connection. Connect the white/green wire (P2 pin 2) to the ring
connection.
WIRING INSTRUCTIONS
Connections should be made as shown in Figure 4 and indicated in Tables
1 and 2. Read also the referenced notes below. If longer wire lengths are
required, use a good quality multi stranded hook-up wire - 22 gauge or larger.
Although not necessary, shielded audio wire can be used if desired.
1. The blue wire from Pin 3 must be connected to the aircraft radio headphone
output - NOT the speaker output. NOTE – If aircraft radio volume heard in
the headsets changes significantly when switching the ON/OFF switch
a minor adjustment to the radio receive potentiometer will fix this. See
“INSTALLATION CHECK-OUT AND ADJUSTMENTS” section on page 4.
2. Connect all intercom mic jack grounds to a single aircraft chassis ground
point - Intercom Central ground Point “A” - as shown in Figure 4. (Use the
black washers supplied to insulate the intercom mic jacks from aircraft
chassis ground). Note this intercom central grounding point is used to
eliminate any unwanted electrical noises, such as alternator whine or
strobe noise, from being induced into the intercom system through the
grounds. All intercom mic jack barrels must be insulated from ground
where they are mounted and connected back to Intercom Central Ground
Point “A” on their own individual ground wire. Similarly, both intercom
ground wires (J1 pin 4) and the push-to-transmit switch grounds must
also be connected back to Intercom Central Ground Point “A”. It is not
necessary, however, to connect the headphone jack barrels to Intercom
Central Ground Point “A”. They can either be grounded where they are
mounted or some place nearby.
3. The red wire may be connected to either 12V (14V) or 24V (28V) power
source. No switching or adjustments are required to operate from either
source.
4. Tan wires (J1 pins 8, 9) are only used on installations that require the two
rear intercom positions.
5. The SPA-4S system provides a stereo music input. This music input accepts
portable music Headphone or Line level music sources. The wiring diagram
shows how to wire the SPA-4S for
use with a portable stereo music
source. A small stereo input jack is
supplied for this purpose. Connect
the White/Brown, White/Violet, and
Black wires to one jack as shown in
Figure 4. Identify the jack terminals
using Figure 5. Drill a 1/4-inch hole
for the jack and mount on the aircraft
panel. To use, connect an adapter
cable between the music input
jack and the output of the portable
stereo. Suitable cables are available at your local Stereo or electronics store
as well as from Sigtronics. Speaker level output car stereo music sources
can also be used with the SPA-4S system. A Floating Ground Adapter or a
four wire to three wire converter will have to be used between the Stereo
and the SPA-4S music input. Figure 6 shows such an adapter and how it is
wired into the SPA-4S.
6. The Sigtronics SPA-4S system can be installed as shown for use with
Stereo headsets. Alternatively, monaural general aviation type headsets
can be used. To use monaural headsets follow the installation instructions
as normal except for the wiring of the stereo headphone jacks. Use the
stereo headphone jacks supplied with the Sigtronics SPA-4S but leave the
“RING” connections open. Instead connect both headphone wires to the
“TIP” of the respective jacks. Connect both the WHITE/GREEN and GREEN
on to the TIP of the headphone jack.
7. The Violet wire (J1 pin 12) is provided on SPA-4SN models only for an
optional Push-to-intercom function. For wiring and additional instructions
on the SPA-4SN see the “SPA-4SN PUSH-TO-INTERCOM INSTRUCTIONS”
section on page 4. Make sure any unused wires are properly insulated
and kept from shorting to any other wires or aircraft ground. Skip to the
“INSTALLATION CHECK OUT AND ADJUSTMENT” section on page 4.
UPGRADING A SPA INSTALLATION TO A SPA-4S
Chassis Mounting
The SPA-4S is specifically designed to easily replace a SPA-400. The intercoms
are exactly the same dimensions (1” x 2.5” x 4”). Five mounting holes are
exactly in the same positions. To upgrade, first remove the SPA-400 unit from