sides. Insert edges of folded tape into
voice coil gap to full depth, and wipe
clean completely around circular peri-
meter of tangerine phasing plug® and
top plate (see Figure 5). Repeat cleaning
procedure several times with fresh tape
until tape is clean when withdrawn .
Figure 5. Cleaning Voice Coil Gap
8. Carefully place new diaphragm and
voice coil assembly in proper posit ion to
align screw holes. Use care to avoid
damaging edge and sides of voice coil
while positioning it in voice coil gap. Be
sure voice coil/diaphragm assembly is
fully seated.
9. For Models 902-SA and 902-16A, install
screws removed in Step 5. Tighten
screws securely.
For Model 902-ST, install acoustical
loading cap, using screws removed in
Step 5. Tighten screws securely .
------CAUTION------,
If new screws are required to secure
the acoustical loading cap and/or the
voice coil/diaphragm assembly, use
brass screws only.
10. Connect two leads of driver cover to
internal binding posts . Connect red lead
to post designated +, and black lead to
opposite post. Tighten screws securely.
11. Install cover of driver, securing with
screws removed in Step 3.
12. Return driver to service; connect exter-
nal leads to binding posts . Take care to
maintain electrical phasing (polarity) as
originally wired .
Prevention of Possible Speaker Damage
from RF and Static Charges
The 70-volt lines leading to outdoor speake r
installations may develop a substantial
voltage to ground at radio frequencies,
owing to the proximity of high power radio
and radar transmitting stations. Un-
grounded speaker lines are also subject to
accumulated static charges under atmos -
pheric conditions . A discharge in the voice
coil gap, from either of these causes, may
be prevented by the following means; such
means are recommended whenever the
speakers are mounted on an insulated sup-
port (e.g., a telephone pole or wooden
tower) .
1. When the 70-volt line is 'floating ' (i.e., no
ground con nection exists at either side
of the amplifier output to the speake r
line):
A 0.005 µF, 200-volt ceramic capacitor
should be connected from each side of
the 70-volt transformer primary to the
frame of the horn or driver , to bypass
the 70-volt speaker line (see Figure 6).
Each speaker line should be bypassed
in this manner at one speaker of the
HORN OR THROAT
FASTENING NUTS
DRIVER HOUSING
VOICE
COIL
GROUND WIRE
(12 GA. OR LARGER
array . A wire, 12 gauge or larger, should
be connected between the horn frames
or driver housings of all horns . After all
horns are inter connected in this
manner, a single wire, 12 gauge or
larger, is run fro m one horn or driver
housing to ground (earth - by means of
a suitable driven ground; water pipe,
etc .). A 10,000-ohm resistor is then con-
nected between one of the 70-volt
output terminals and ground at the
amplifier location (see Figure 7).
I
I
l>
<. 10K
AMPLIFIER
OUTPUT
TRANSFORMER
SECONDARY
:> (SEE TEXT)
< >
(
I
__.__
Figur e 7. Grounding 70-Volt
Output Terminal
2. When the 70-volt speaker line is already
grounded at the amplifier output :
The preceding instructions continue to
apply, with regard to the RF bypass
within the speaker housing itself and
the grounding of the horn frame or
driver housing of each horn ; however ,
the 10,000-ohm resi stor at the amplifier
location may be om itted.
.005
200V
.005
200V
70 VOLT
SPEAKER LINE
GROUNDED TO DRIVER HOUSING
MOUNTING SCREWS
Figure 6. Preventing Damage from RF and Static Charges
-2-
