Shure SR105 service manual Table of Contents

SR105 Power Amplifier

TABLE OF CONTENTS

Section	Page
SPECIFICATIONS	. ii
DESCRIPTION	. 1
OPERATING INSTRUCTIONS
Functional Identification	. 3
General Operating Instructions	. 3
Mounting and Ventilation	. 4
Thermal Overload	4
Power Requirements	. 4
Functional Circuit Description	4
Input Connections	. 4
Output Connections	. 6
Amplifier-to-Speaker Impedance Matching	. 8
Output Voltage Meter	9
Basic Operating Hints	. 10
SPECIAL OPERATING INSTRUCTIONS
Adding SRlO5A Amplifiers in a
70-Volt System (Cascaded)	.10
Bridging Connections	11
Adding Headphone Jack to Speaker Connections . .	. 11

SERVICE INSTRUCTIONS

Amplifier Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Section Page

Replacement Parts . . . . . . . . . . . . . . . . . . . . . . . . . . .12.

Fuse Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Bottom Plate Removal . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Cover Removal . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Lamp Replacement . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12

Dc Output Balance Adjustment . . . . . . . . . . . . . . . . . . . 12

Output Voltage Meter Calibration . . . . . . . . . . . . . . . . . 12

Printed Circuit Board Removal . . . . . . . . . . . . . . . . . . .13

Small Signal and Predriver Transistors . . . . . . . . . . . . 14

Driver Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14

Output Transistors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Diodes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Diode Bridge Rectifier . . . . . . . . . . . . . . . . . . . . . . . . . . 15

Checking Transistors and Diodes . . . . . . . . . . . . . . . . . 15

SR105B Amplifier Conversion for 70-Volt Output . . . .15

Service lllustrations . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Guarantee . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

Shipping Instructions . . . . . . . . . . . . . . . . . . . . . . . . . . . 17

PARTS LIST . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19

CONDENSED OPERATING INSTRUCTIONS . . . . . . . . . 27

ARCHITECTS' AND

ENGINEERS'SPECIFICATIONS . . . . . . . . . . . . . . . 27

SR105 Power Amplifier

LlST OF ILLUSTRATIONS

Figure		Page
1	SR105 Power Amplifier Front Panel	. 2
2	SR105 Power Amplifier Rear Panel	. 2
3	SR105 Power Amplifier Dimensional
	Outline Drawing	4
4	SR105 Power Amplifier Block Diagram	. 5
5	Input Connections	6
6	Output Power vs. Load lmpedance from
	2 Ohms to 32 Ohms	7
7	70-Volt Output Power vs. Direct Output Load
	Impedance from 4 Ohms to 100 Ohms	. 7

8Recommended Wire Gauge vs. Amplifier-to-

Speaker Distance: Direct Output . . . . . . . . . . . 8

9Recommended Wire Gauge vs.Amplifier-to-

Speaker Distance: 70-Volt Output

(SR105A Only) . . . . . . . . . . . . . . . . . . . . . . . . . . 8

Figure Page

10 70-Volt System Attenuator . . . . . . . . . . . . . . . . . . . 11 11 Bridged Amplifier Connections . . . . . . . . . . . . . . . 11 12 Headphone Jack for Speaker Connections . . . . .11 13 SR105 Power Amplifier Top View, Cover

Removed (SR105A Model Shown) . . . . . . . . . . 13 14 SR105 Power Amplifier Bottom View.

Cover Removed (SR105A Model Shown) . . . . .14 15 70-Volt Conversion: Added Circuitry . . . . . . . . . .16 16 70-Volt Conversion: Transformer Mounting . . . . .17 17 70-Volt Conversion: Internal Wiring . . . . . . . . . . . 18 18 Main Circuit Board Parts Location Diagram . . . .22 19 Filter Circuit Board Parts Location Diagram . . . .22 20 Transistor Lead Codes . . . . . . . . . . . . . . . . . . . . .23 21 SR105 Power Amplifier Circuit Diagram . . . . . . . 25