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SR105 Power Amplifier
OPERATION AND SERVICE MANUAL
Manufactured by
SHURE BROTHERS INC.
222 Hartrey Avenue
Evanston, Illinois 60204 U.S.A.
WARNING
To reduce the risk of fire or electric shock, do not
expose this appliance to rain or extreme moisture.
Copyright 1979, Shure Brothers Inc.
Printed in U.S.A.
27A888 (SJ) (95B652)
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SR105 Power Amplifier SPECIFICATIONS The following specifications apply to both SR105A and SR105B Power Amplifiers except where noted. The SR105A Power Amplifier provides both direct-coupled speaker output and transformer-coupled, constant-voltage, 70-volt output. The SRlO5B Power Amplifier is equipped for direct-coupled speaker output only. Amplifier Type ....... All silicon transistor power Load Regulation: amplifier Di rect-Coupled Power Output ....... .200 watts rms continuous to Spea
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SR105 Power Amplifier SPECIFICATIONS (Curves shown are typical) FREQUENCY (Hz1 OUTPUT POWER (WATTS) OUTPUT POWER VS. FREQUENCY AT 1% 81 2% TOTAL HAR- TOTAL HARMONIC DISTORTION VS. OUTPUT POWER TO MONIC DISTORTION TO 4-OHM LOAD (DIRECT OUTPUT 4-OHM LOAD AT 50 HZ, 1 KHZ & 10 KHz (DIRECT OUTPUT ONLY) ONLY) LOAD RESISTANCE, OHMS OUTPUT POWER (WATTS) TOTAL HARMONIC DISTORTION VS. OUTPUT POWER (VAR- IOUS LOADS) AT 1 KHz AND CONSTANT 70.7V OUTPUT (70V OUTPUT ONLY)* FREQUENCY ( H J OUTP
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SR105 Power Amplifier TABLE OF CONTENTS Section Page Section Page ............................... ............................ SPECIFICATIONS ii Replacement Parts 12 ............................. Fuse Replacement 12 DESCRIPTION .................................. 1 .......................... Bottom Plate Removal 12 OPERATING INSTRUCTIONS ................................ Cover Removal 12 ........................ Functional Identification 3 ............................ Lamp Replace
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SR105 Power Amplifier DESCRIPTION (Shown in A105A Carrying Case) tional 70-volt output feature of the SR105A Power Amplifier The Shure SR105 Power Amplifier is a high-power ampli- fier designed for sound reinforcement applications. It is makes it equally adaptable to source-oriented or distrib- capsble of delivering 200 watts rms to a 4-ohm load, and is uted speaker systems such as those used for background available in two models, the SR105A and SR105B. The music or announcements in ind
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FIGURE 1. SR105 POWER AMPLIFIER FRONT PANEL FIGURE 2. SR105 POWER AMPLIFIER REAR PANEL (SR105A MODEL SHOWN)
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SR105 Power Amplifier OPERATING INSTRUCTIONS (4,lO) to OFF and VOLUME Control (2) FUNCTIONAL IDENTIFICATION (Refer to Figures 1 and 2, 2. Set Switches Page 2). to 0. 3. Connect required speakers to Amplifier DIRECT OUT- 1. OUTPUT VOLTAGE Meter - lndicates Amplifier out- PUT jacks (8) andlor to terminal strip (9), using proper put voltage in percentage of maximum voltage. wire size and arranging speaker connections for total 2. VOLUME Control - Controls Amplifier output level. speaker
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MOUNTING AND VENTILATION spare ac power fuse is supplied for mounting in the clip on the rear panel (12). The SR105 Power Amplifier is designed for rack-mount- Additional protection is provided by wired-in fuses in the ing in a standard 19-inch (483 mm) audio equipment cabinet main ac power circuit (FI, 8 amperes) and in the ac pilot rack and is supplied with the necessary mounting hardware. lamp circuit (F3, 1 ampere). These fuses are located under To insure adequate air circulation, a
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VOLT- METER METER RECTIFIER (70) INPUTS I' 0'' - UNBALANCED METER DIRECT ADJUST SPEAKER a I OUTPUTS / BALANCED 11 BRIDGING ? = '0 LOW-CUT 70 V INPUT VOLUME FILTER d XFMR ASSEMBLY !& / I I - I I I I f !& SRIOSA AMPLIFIER ONLY. I I I BALANCE I 1 1 I I I I I I XFMR* * I I I I L - - - - - - - - - - - - - - - - - - - -1 FIGURE 4. SR105 POWER AMPLIFIER BLOCK DIAGRAM Additional SR105 Power Amplifiers may be added to the In applications where the Amplifier
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@ UNBALANCED PARALLELED MIXER- POWER PREAMPLIFIER AMPLIFIER 0 I I I I \/ \A I UNBALANCED PARALLELED HIGH-IMPEDANCE INPUTS 0 TO POWER AMPLIFIER A - - OR HIGH-IMPEDANCE TAPE RECORDER INPUT BALANCED BRIDGING INPUT TO POWER AMPLIFIER OR OTHER AUXILIARY EQUIPMENT + I - SR105 MIXER- POWER PREAMPLIFIER AMPLIFIER @ SLEEVE 6-TT- 5 570,114 W TIP FIGURE 5. INPUT CONNECTIONS OUTPUT CONNECTIONS ohms should not be used with this Amplifier. If less than four ohms is inadvertentl
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CAUTION Parallel connection of the DIRECT OUTPUT Con- nectors (8,9), or the speaker cables between two SR105 Power Amplifiers, or the SR105 Amplifier and any other amplifier, should not be attempted. Bal- ancing paralleled amplifiers is virtually impossible, and the circuitry mismatch cannot be balanced. The same precaution should be observed with regard to the 70V OUTPUT Connectors (11) of two SR105A Amplifiers, or the SR105A Amplifier and any other amplifier. Such a connection may re
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to reduce the wire size in increments as the speaker load AMPLIFIER-TO-SPEAKER DISTANCE (FEET1 becomes less toward the end of the cable run or as 200 400 600 800 1000 1200 branches are split off the main line. The economy of such 36 an arrangement will vary depending upon the details of - 32 each installation and should be evaluated accordingly. 0) i 28 Y AMPLIFIER-TO-SPEAKER IMPEDANCE MATCHING 2 24 DIRECT SPEAKER OUTPUT Y 0 In order to obtain maximum transfer of Amplifier power
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wattage rating applicable to each tap. For example, the dance may be calculated by the formula: Shure A102A, a 50-watt transformer, has taps at 50, 25, 12 1 1 1 1 and 6 watts. (Transformers are available at various power -=- f-+- . . . . etc. ratings to suit the requirements of the application.) The pri- ZT ZI 22 Z, mary taps allow adjustment of the power level delivered to the speaker when the transformer is connected to the 70- where ZT is the total impedance, Z, is the impedance of
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Meter Reading Output Power 1. Check that ac power source is "live" and 100% 1 X that Amplifier is plugged in. 86.7% 3/4X 2. Check that POWER ON-OFF Switch (4) is 70.7% 1 /2X on. 50 % 1 /4X 3. Check to see that rear-panel 3AG/5A Fuse 33.3% 1/10X (6) is good. 10% 1/1oox 4. Check that THERMAL OVERLOAD Lamp (3) is not lit. In most applications, the VOLUME Control (2) setting Amplifier is "dead" (no output, OUTPUT VOLT- Symptom: of the Amplifier is determined by the sound level requi
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duce approximately 28.3 volts at the DIRECT OUTPUT Qty. Part Recommended Type 1 Phone Jack Switchcraft 12-8 terminals (8,9), or 70 volts at the 70V OUTPUT terminals 1 Phone Plug Switchcraft 280 (11) when the 70-volt input line is supplying 70 volts. 1 Volume Control Switchcraft 666Pl or 656 (L-Pad) 70-VOLT LINE 1 Transformer, 25V Essex-Stancor A-8095 * 3-PIN MALE Line to Voice Coil or A-8096 AUDIO CONNECTOR ATTENUAm r---i Connect the parts as shown in Figure 12, Page 11. Make I .
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SR105 Power Amplifier SERVICE INSTRUCTIONS AMPLIFIER SERVICE (See Guarantee) COVER REMOVAL The SR105 Power Amplifier uses components of the high- To service components on the top of the chassis, the est quality, operating well within their respective ratings to protective cover grille (MP7) must be removed. This is assure long life. done by removing one screw from the top, two screws from each side, and eight screws from the back surface. To re- move, slide cover up and to the rear of the
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R39 R40 Dl2 R36 T2 C14 C15 R3 1 Q8 R35 Q7 R43 PL2 MI PL3 (XPL2) (XPL3) Y SRIOSA MODEL ONLY FIGURE 13. SR105 POWER AMPLIFIER TOP VIEW, COVER REMOVED (SRlOSA MODEL SHOWN) Circuit Board. (The SR105B Amplifier contains only a Main adjustment screw below the meter face until the needle is Circuit Board.) The foil side of the boards may be made properly positioned. With no load on the Amplifier (speaker accessible for servicing without disconnecting any leads disconnected), connect an ac vo
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SMALL SIGNAL AND PREDRIVER TRANSISTORS Main Circuit Board Transistors Q1 through Q6, Q13, Q14, and Q201 through Q203 are mounted on printed circuit boards. When re- placing these transistors it is imperative that proper lead Letter Wire Color Letter Wire Color configuration be followed. A minimum of soldering heat should be used to avoid damage to the transistor or printed A Blue J Yellow/Black circuit board. Refer to the Notes to Circuit Diagram (Figure B Black K Orange/Black 20, Pag
