Specifications

2. Remove upper rear panel as described in Speak-
er Servicing above.
3. Unsolder high-frequency driver assembly leads
(black and green) from inductor assembly L2,
and place a dummy load (16 ohms, 50 watts
minimum) across L2.
4. Connect an ac voltmeter
(Simpson 260 or equi-
valent) across dummy load.
5. Apply a
5 kHz ac voltage from a power amplifier
across one
HlGH FREQ/BIAMP OPERATION In-
put Jack (J5 or J6). Slowly increase voltage
until 28
Vac is reached. Relay K1 should open,
as indicated by ac voltmeter reading suddenly
dropping to approximately 13
Vac. If it does
not, adjust rheostat
R10 until relay K1 operates
as input voltage reaches 28
Vac. Remove input
voltage to release relay.
6. Remove ac voltage, disconnect dummy load and
voltmeter, and
resolder high-frequency driver
leads. Replace rear panel and tighten all screws
securely to avoid rattles.
Radial Horn Replacement
To replace the
SR108 high-frequency radial horn,
follow these
stem:
1. Remove 10 #8 Phillips head screws securing
horn to front of enclosure.
2. Lift horn outward from front of enclosure, insert
new horn, and replace 10 Phillips head screws.
3. Replace foam screen in horn throat, apply
PLIO-
BOND (or equivalent) cement around edges to
hold it in place. Make sure all hardware is tightly
fastened to avoid rattles.
Grille Assembly Replacement
To remove and replace the
SR108 front-panel grille
assembly, follow these steps:
1. With
SR108 lying flat on a firm surface, use a
short length of wood (2 in.
X 4 in. is recom-
mended) to apply firm, steady pressure at cen-
ter of grille approximately one-third distance
from top.
2. As grille is pushed back, edges will appear in
left and right slots. Use a screwdriver or knife
to gently pry edges of grille up over edge of
slot on either left or right side.
3. Begin removing grille assembly from top, taking
care not to scratch enclosure with edge of grille.
2
WARNING
Grille assembly is under tension and effec-
tively presents a spring-loaded rough edge
as it is removed. Take care not to handle
assembly at edges during removal.
4. As grille edge near top comes free, move hand
applying pressure and screwdriver edge down-
ward to free remainder of grille.
5. Replace new grille assembly by centering it in
enclosure, and applying pressure at center until
grille assembly "pops" into slots.
Wheel Assembly Replacement
To replace a wheel or other parts of the
SR108
wheel assembly, follow these steps (see Figure R):
1. Place SR108 face downward on flat surface and
remove lower rear panel as described in Speak-
er Servicing.
2. While holding
3/4 in. locknut with a socket
wrench, insert a
%I in. Allen wrench in wheel
assembly
capscrew and unscrew capscrew from
the assembly.
3. With locknut, flat washer and
capscrew removed,
wheel and bushings may now be removed.
4. When reassembling wheel assembly, be sure
to replace flat washer before tightening locknut.
Tighten
capscrew and locknut firmly.
5. Install back panel and tighten securely to avoid
rattles.
Model
RKC149 Crossover Assembly
A complete crossover assembly may be obtained
from Shure Brothers Inc. as Model
RKC149. This as-
sembly provides complete facilities for high- and
low-frequency signal separation, and overvoltage pro-
tection. A general description of the crossover as-
sembly is included in the CIRCUIT DESCRIPTION
section, and biamplified operation is described in the
BlAMPLlFlCATlON section.
The Model
RKC149 consists of the components listed
in Table 1 (refer to Figures
M and P, and the Replace-
ment Parts List).
The LOUDSPEAKER OPERATION switch
(Sl) con-
tains the following settings:
Position 1 (full CCW):
FULL RANGE -4 dB
Position 2:
FULL RANGE -2 dB
Position 3: FULL RANGE
0 dB
Position 4: FULL RANGE
+2 dB
Position
5 (full CW):
BlAMPLlFlED
Connector PI is a nine-pin connector in which eight
pins are connected as follows (see Figures M and P):
Pin 1: FULL RANGE common input
LOW FREQ common input
Low-frequency speaker common output
Pin 2: LOW FREQ "hot" input
Pin 3:
HlGH FREQ "hot" input
Pin
4: HIGH FREQ common input
Pin 5: Low-frequency speaker "hot" output
Pin 6: FULL RANGE "hot" input
Pin
7: High-frequency driver common output
Pin 8: High-frequency driver "hot" output
GUARANTEE
This Shure product is guaranteed in normal use to
be free from electrical and mechanical defects for a
period of one year from the date of purchase. Please
retain proof of purchase date. This guarantee in-
cludes all parts and labor.
SHIPPING INSTRUCTIONS
Carefully remove the defective part without damag-
ing the unit, repack it, and return it prepaid to the
factory. If outside the United States, return the part
to your Authorized Shure Service Center for repair.
The part will be returned to you prepaid.
For service or instructions on the complete speaker
system or enclosure, contact your Authorized Shure
Service Center or the Shure Factory.