Specifications

on which set of four speakers is suspect. Removal
of these speakers will provide access to the wiring
associated with the other speakers of that set.
(NOTE: If a power screwdriver is used to remove the
retainer strip screws, excessive force may loosen
the
teenuts and cause them to drop into the en-
closure.) Remove the
&inch speaker by removing
the four locknuts and flat washers (using an 11/32"
nutdriver), and gently lifting the speaker out and
resting it on the baffle board.
6. Using an ohmmeter, measure the resistance of
each speaker voice coil in the set. A clicking sound
will be made by a "good" speaker when an ohm-
meter is connected or disconnected. Note that the
high-frequency speakers
(LS2, LS7) cannot be
properly measured without unsoldering the asso-
ciated inductor
(L1, L2; see Figure K) though
the "click" produced by the ohmmeter can be
heard without unsoldering the inductor. Each
10-
inch speaker should measure between 10 and 14
ohms. Each 8-inch speaker should measure be-
tween
6 and 8 ohms. Each high-frequency speaker
should measure between 13 and 15 ohms. Readings
outside these limits indicate possible failures. Re-
place any speakers found defective.
7. If the above tests do not locate the defective unit,
apply a small ac voltage from a sweep oscillator
and amplifier to each speaker individually (approxi-
mately 4V, 50 to
10 kHz for 8- and 10-inch speakers;
approximately 2V, 3 kHz to 15 kHz for
high-fre-
quency speakers).
WARNING
Sound pressure levels generated by this
test may be damaging to your hearing. Aim
speakers away from listeners and toward
sound-absorbent material (curtains, blanket,
etc.). Carefully adjust test signal amplitude
to avoid unnecessarily high sound pressure
levels for prolonged periods.
As the test signal frequency is varied, any erratic
buzzes or rattles indicate possible failure.
8. Reconnect the high-frequency speaker inductors
and replace and tighten the
&inch speakers. Re-
place
.the vertical retainer strip, grille and pad as-
sembly, and color and trim strips. Tighten all hard-
ware to avoid rattles.
High-Frequency Speaker Diaphragm and
Coil Assembly Replacement
The high-frequency speakers
(LS2, LS7) may be
supplied in either of two configurations. Type
I em-
ploys three screws and three 8-32 x 11/32" nuts to
hold the horn to the magnetic structure. Type
II em-
ploys three screws and three threaded holes in the
circular mounting flange of the horn to hold the horn
to the magnetic structure.
Replace the diaphragm and coil assembly in the
high-frequency speaker as follows:
1. Remove the high-frequency speaker irom the
enclosure by first removing the 10" speaker
next to it.
COLOR-CODED TERMINAL
TS
I 7,
TOP
SET
FIGURE K. CIRCUIT DIAGRAM
2. Remove the three 8-32 x 11/32" locknuts and
washers securing the speaker to the baffle. Do
not allow the speaker to drop into the enclosure
when removed.
3. Unsolder the leads connected to the speaker
terminals and remove the speaker from the
enclosure.
4. Prepare a clean work area, free of drafts and
metallic dust and chips. Cover the work area
with clean kraft paper or newspaper.
5. Place the speaker on the work surface.
a. Type I: Remove the three 8-32
x 11/32" nuts
and screws securing the horn to the mag-
netic structure; remove the horn (see
~igure
L).
b. Type II: Remove the three screws securing
the horn to the magnetic structure; remove
the horn (see Figure L).
6. Remove the diaphragm and coil assembly by
lifting upward. This is a snug fit, and a gentle
prying force may be required.
7. Clean the voice coil gap in the magnetic struc-
ture as follows. Insert a strip of masking tape
into the voice coil gap with the adhesive side
outward. Draw the tape around the gap several
times to provide good wiping action. Repeat the
process with a new piece of tape with the
adhesive side facing inward.