Pioneer SX-939 Service Manual

<ART-044-0>
SERVICE MANUAL
STEREO RECEIVER
KCU, F, GN
NOTE:
MODEL SX-939 COMES IN THREE VERSIONS DISTINGUISHED AS FOLLOWS:
Round label on
rear panel
Voltage
Type
KCU 120V only
UL (U.S.A.) and CSA (Canada) approved.
F
110V, 120V, 130V
220V and 240V
(switchable)
General export model
GN
—
220V only
SEMCO (Sweden), NEMCO (Norway) and
DEMCO (Denmark) approved.
<74B02M61D> CD PIONEER

Pioneer SX-939 Specifications

General

Tuning Range	FM, MW
Damping Factor	30
Input Sensitivity	2.5 mV (MM), 150 mV (line)
Output	150 mV (line)
Frequency Response	10Hz to 30 kHz
Total Harmonic Distortion	0.3%
Signal to Noise Ratio	90dB (line)
Speaker Load Impedance	4 ohms to 16 ohms
Semiconductors	4 x IC

Summary

1. SPECIFICATIONS

2. FRONT PANEL FACILITIES

SPEAKER BUTTONS

Controls for connecting speaker systems A, B, and C.

PHONES (1, 2) OUTPUT JACKS

Jacks for connecting two pairs of headphones.

BASS CONTROLS

Controls for adjusting bass tone quality at 100Hz and 50Hz.

LOW CUT, HIGH CUT BUTTONS

Buttons to reduce low-frequency rumble or high-frequency scratch.

TONE SWITCH

Switch to enable flat frequency response regardless of tone controls.

TREBLE CONTROLS

Controls for adjusting treble tone quality at 10kHz and 20kHz.

AUDIO MUTING BUTTON -20dB

Button to mute audio input by -20dB without turning volume down.

TAPE DUPLICATE SWITCH

Switch for tape duplication or editing between two tape decks.

SIGNAL METER

Meter for AM and FM station tuning.

FM TUNING METER

Fine adjustment meter for FM reception.

FM STEREO INDICATOR

Indicator for FM stereo reception.

TUNING KNOB

Knob used for tuning AM and FM stations.

FUNCTION SELECTOR BUTTONS

Buttons to select program source (AM, FM, PHONO, AUX).

POWER SWITCH

Switch to turn the unit on and off.

DIMMER SWITCH

Switch to adjust the brightness of indicator lights.

FM MUTING BUTTON

Button to suppress inter-station noise during FM tuning.

LOUDNESS BUTTON

Button to compensate for hearing response at low volumes.

MIC INPUT JACKS

Jacks for connecting microphones.

VOLUME CONTROL

Control for overall sound volume for speakers and headphones.

MODE BUTTON

Button to select between STEREO and MONO playback.

3. CONNECTION DIAGRAM

4. BLOCK DIAGRAM

5. CIRCUIT DESCRIPTION

SIGNAL PATH

Describes the signal flow through the unit.

6. LEVEL DIAGRAM

7. DISASSEMBLY

8. PARTS AND P.C. BOARD LOCATIONS

9. DIAL CORD STRINGING

10. ALIGNMENT PROCEDURE

10.1 ENGLISH

Alignment procedures for the FM section in English.

ALIGNING THE FM MPX SECTION

Alignment procedures for the FM Multiplex section.

ALIGNING THE AM SECTION

Alignment procedures for the AM section.

ALIGNING THE POWER AMPLIFIER SECTION

Alignment procedures for the power amplifier section.

11. EXPLODED VIEW AND PARTS LIST

12. SCHEMATIC DIAGRAMS, P.C. BOARD PATTERNS AND PARTS LIST

2.1 CIRCUIT CONNECTION DIAGRAM AND MISCELLANEOUS PARTS

Circuit connection diagram and a list of miscellaneous parts.

12.2 TUNER ASSEMBLY (AWE-041-0)

Schematic and PCB layout for the Tuner Assembly.

12.3 MUTING CIRCUIT ASSEMBLY (AWM-063-0)

Schematic and PCB layout for the Muting Circuit Assembly.

12.4 EQUALIZER AMPLIFIER ASSEMBLY (AWF-013-0)

Schematic and PCB layout for the Equalizer Amplifier Assembly.

12.5 CONTROL AMPLIFIER ASSEMBLY (AWG-027-0)

Schematic and PCB layout for the Control Amplifier Assembly.

12.6 POWER AMPLIFIER ASSEMBLY (AWH-030-0)

Schematic and PCB layout for the Power Amplifier Assembly.

12.7 PROTECTION CIRCUIT ASSEMBLY (AWM-062-0)

Schematic and PCB layout for the Protection Circuit Assembly.

12.8 POWER SUPPLY CIRCUIT ASSEMBLY (AWR-052-0)

Schematic and PCB layout for the Power Supply Circuit Assembly.

12.9 SWITCH CIRCUIT ASSEMBLY (AWS-064-0)

Schematic and PCB layout for the Speaker Switch Circuit Assembly.

12.10 SWITCH CIRCUIT ASSEMBLY (AWS-065-0)

Schematic and PCB layout for the Mode/Loudness Switch Circuit Assembly.

12.11 SWITCH CIRCUIT ASSEMBLY (AWS-066-0)

Schematic and PCB layout for the Filter/Muting Switch Circuit Assembly.

12.12 SWITCH CIRCUIT ASSEMBLY (AWS-067-0)

Schematic and PCB layout for the Function/Monitor Switch Circuit Assembly.

12.13 SWITCH CIRCUIT ASSEMBLY (AWS-068-0)

Schematic and PCB layout for the Dimmer/FM Muting Switch Circuit Assembly.

12.14 SWITCH CIRCUIT ASSEMBLY (AWS-069-0)

Schematic and PCB layout for the Function Selector Switch Circuit Assembly.

12.15 5P CONNECTOR ASSEMBLY (AWX-062-0)

Schematic and PCB layout for the 5P Connector Assembly.

13. PACKING METHOD AND PART NUMBERS

14. SCHEMATIC DIAGRAMS, P.C. BOARD PATTERN AND PARTS LIST FOR 220V ONLY MODEL

4.1 CIRCUIT CONNECTION DIAGRAM AND MISCELLANEOUS PARTS

Circuit connection diagram and miscellaneous parts for the 220V model.

14.2 POWER SUPPLY CIRCUIT ASSEMBLY (AWR-056-0)

Schematic and PCB layout for the 220V Power Supply Circuit Assembly.