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as shown in Figure 158, Page 13, and plug the control
assembly into the LlNK OUTPUT (21) and LlNK INPUT
(22) Jacks.
For distances over 15m (50 ft) or for permanent instal-
lations where hum or noise may be encountered, use
low-capacitance, two-conductor, shielded cable (Bel-
den #8412 or #8422). Connect as shown in Figure 15C,
Page 13, and use a metal box to contain the potenti-
ometer. The cable shield must be connected to the metal
box containing the potentiometer, to the common con-
ductor (black), and not to the sleeve connections of the
phone plugs. IMPORTANT: To avoid hum caused by a
ground loop, do not ground the metal box to any metal
such as electrical conduit, water pipes, heating ducts, or
structural steel.
TELEPHONE LINE SURGE PROTECTION
When using the Mixer to feed a telephone line that may
be subject to lightning-induced voltage surges, the follow-
ing part should be installed across the telephone line to
provide additional protection for output circuit compon-
ents: Thyrector, General Electric Part No. 6RS20SPlBl.
SR109 Professional Mixer
SERVICE INSTRUCTIONS
MIXER SERVICE (SEE GUARANTEE, Page 35.)
CAUTION
The SR109 Professional Mixer uses components of the
If trouble symptoms -overheating,
erratic op-
highest quality, operating well within their respective rat-
eration, etc. -were
apparent before the fuse
ings to assure long life.
blew, or if the replacement fuse blows, a quali-
fied serviceman should troubleshoot the Mixer
W A R N I N G
Voltages in this equipment are hazardous to life.
Make all input and output connections before ac
power is connected. Refer servicing to qualified
service personnel.
REPLACEMENT PARTS
Parts that are readily available through local electronics
parts distributors are not shown on the accompanying
Parts List. Their values are shown on the Circuit Diagram
(Figure 25, Pages 32-33). Commercial parts not readily
available and unique parts are shown on the Parts List
and may be ordered directly from the factory.
The commercial alternates shown on the Parts List
are not necessarily equivalents, but may be used in the
event that direct factory replacements are not immediately
available. To maintain the highest possible performance
and reliability, Shure factory replacement parts should be
used. When ordering replacement parts, specify the Shure
Replacement Kit Number (RKC), description, product
model number, and serial number.
FUSE REPLACEMENT
To replace line fuse F1 (with no apparent problems in
the Mixer), disconnect the line cord from the ac source
and remove the rear-panel fuseholder cap. Replace the
defective fuse only with a 3AG-3/16A Slo-Blo fuse
(SR109 only; SR109-2E contains a 0.1A Slo-Blo fuse for
180- to 250-volt operation, or a 0.2A Slo-Blo fuse for 90-
to 132-volt operation).
carefully to find the source of the trouble. Do
not continue to replace fuses until the trouble has
been corrected.
The Mixer also contains a wired-in fuse in series with
rear-panel line fuse F1 (F2, 3/10A, Slo-Blo). If replacement
becomes necessary, replace only with an identical fuse.
KNOB REPLACEMENT
All front-panel control knobs are pull-off types and are
interchangeable with others of the same function. When
ordering replacement knobs, be sure to order the proper
color-coded type for the desired control.
SERVICE ACCESS
To open the Mixer for servicing, remove the eight Phil-
lips head screws securing the top cover and remove the
top cover. Rear-panel-mounted parts and the preamplifier
assembly may be reached by removing the eight Phillips
head screws securing the rear panel, and carefully moving
the rear panel assembly out and downward. Front-panel-
mounted parts may be reached by removing the two screws
at the top of the cover channels and the four screws at the
bottom of the chassis, and carefully moving the front panel
assembly out and downward.
LAMP REPLACEMENT
To replace either of the two #47 lamps (PLl,PL2) il-
luminating the VU Meter (MI), carefully raise the metal
c l i ~ assemblv holdina the lam^ to be r e ~ l a c e d uoward and
of; the power suppry printed circuit board biacket. Lift
the lamp socket upward, taking care not to crimp or break
any associated wiring. Replace the defective lamp and
carefully return the lamp assembly to its original position.
To replace either of the two light-emitting diodes (LED'S)
(DI,D2) mounted on the front panel, remove the outer
insulating tubing and mounting ring from the rear of the
LED. Press against the front-panel portion of the LED en-
velope to force it out the back through the mounting clip.
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