Sansui 8080DB/9090DB/890DB/990DB AM/FM Stereo Receiver Service Manual

Introduction

This service manual is designed for service engineers to repair, adjust, maintain, and order replacement parts for the Sansui 8080DB/9090DB, 890DB/990DB AM/FM Stereo Receivers. For general usage and maintenance, refer to the Operating Instructions provided with the unit.

Table of Contents

1. SPECIFICATIONS

AUDIO SECTION

POWER OUTPUT

MODEL 8080DB/890DB
Min. RMS, both channels driven, from 20 to 20,000Hz, with no more than 0.1% total harmonic distortion: 85 watts per channel into 8 ohms
Min. RMS, both channels driven, at 1,000Hz, with no more than 0.1% total harmonic distortion: 95 watts per channel into 8 ohms

MODEL 9090DB/990DB
Min. RMS, both channels driven, from 20 to 20,000Hz, with no more than 0.1% total harmonic distortion: 125 watts per channel into 8 ohms
Min. RMS, both channels driven, at 1,000Hz, with no more than 0.1% total harmonic distortion: 135 watts per channel into 8 ohms

LOAD IMPEDANCE

8 ohms

POWER BANDWIDTH

20 to 20,000Hz at or below rated min. RMS power output and total harmonic distortion

TOTAL HARMONIC DISTORTION

less than 0.1% at or below rated min. RMS power output

INTERMODULATION DISTORTION

(70Hz:7kHz 4:1 SMPTE method): less than 0.1%

FREQUENCY RESPONSE (at 1 watt)

10 to 30,000Hz ±1dB

RIAA CURVE DEVIATION (PHONO)

±0.3dB, -0.3dB (30Hz to 15kHz)

DAMPING FACTOR

approximately 30 at 8 ohm load

INPUT SENSITIVITY AND IMPEDANCE (1 kHz, for rated power output)

PHONO-1, 2: 2.5mV/50 kilohms (Max. input capability. 180mV at 1kHz, less than 0.2% total harmonic distortion.)
TAPE-1, 2 PLAY, AUX: 150mV/50 kilohms
MAIN IN: 775mV/100 kilohms

OUTPUT LEVEL (at 1,000Hz)

TAPE-1, 2 REC (pin jacks): 150mV
TAPE-2 REC/PLAY (DIN socket): 30mV
PRE OUT: 775mV

CHANNEL SEPARATION (at rated output 1,000Hz)

PHONO-1, 2: better than 50dB
TAPE-1, 2 PLAY, AUX: better than 50dB

HUM AND NOISE

PHONO-1, 2: better than 70dB
TAPE-1, 2 PLAY, AUX: better than 80dB

*Dolby Noise Reduction effect: 10dB (above 5kHz)

CONTROLS

MODEL 8080DB/890DB
BASS: ±10dB (50Hz)
MIDRANGE: ±5dB (1.5kHz)
TREBLE: ±10dB (10kHz)
LOUDNESS: +8dB (50Hz) +6dB (10kHz)
LOW FILTER: -10dB (50Hz)
HIGH FILTER: -10dB (10kHz)
AUDIO MUTING: -20dB
Tone selector (turnover frequency): 1.5, 3kHz

MODEL 9090DB/990DB
BASS: ±10dB (50Hz)
MIDRANGE: ±5dB (1.5kHz)
TREBLE: ±10dB (10kHz)
LOUDNESS: +8dB (50Hz) +6dB (10kHz)
LOW FILTER: -10dB (50Hz)
HIGH FILTER: -10dB (10kHz)
AUDIO MUTING: -20dB
Tone selector (turnover frequency): 1.5, 3kHz

FM SECTION

MODEL 8080DB/890DB, 9090DB/990DB
TUNING RANGE: 88 to 108MHz

SENSITIVITY

(IHF): 9.8dBf (1.7µV)
(DIN): 0.9µV

50dB QUIETING SENSITIVITY

STEREO (IHF): 36.3dBf (36µV)
MONO (IHF): 14.7dBf (3µV)

TOTAL HARMONIC DISTORTION

STEREO: less than 0.3%
MONO: less than 0.2%

SIGNAL TO NOISE RATIO (mono)

SELECTIVITY: better than 70dB
CAPTURE RATIO: better than 85dB
AM SUPPRESSION: less than 1.5dB
IMAGE RESPONSE RATIO (IHF): better than 55dB
IF RESPONSE RATIO (IHF): better than 70dB (98MHz)
SPURIOUS RESPONSE RATIO (IHF): better than 85dB (98MHz)
SPURIOUS RADIATION: less than 34dB
STEREO SEPARATION: better than 40dB (1 kHz)
FREQUENCY RESPONSE: 30 to 15,000Hz ±2.0dB

ANTENNA INPUT IMPEDANCE

75Ω unbalanced

AM SECTION

TUNING RANGE

535 to 1,605kHz

SENSITIVITY (Bar antenna)

50dB/m (1,000kHz)

SELECTIVITY

better than 50dB (1,000kHz)

IMAGE RESPONSE RATIO (IHF)

better than 30dB (1,000kHz)

IF RESPONSE RATIO (IHF)

better than 30dB (1,000kHz)

OTHERS

MODEL 8080DB/890DB
POWER REQUIREMENTS:
POWER VOLTAGE: 100, 120, 220, 240V 50/60Hz (120V Usable 110-130V, 60Hz for U.S.A. & Canada only)
POWER CONSUMPTION: Maximum consumption: 420 watts, Rated consumption: 265 watts (350VA)
DEMENSIONS: 540mm (21-5/16") W x 182mm (7-3/16") H x 397mm (15-11/16") D
WEIGHT: 20.7kg (45.6 lbs) net, 23.1kg (50.9 lbs) packed

MODEL 9090DB/990DB
POWER REQUIREMENTS:
POWER VOLTAGE: 100, 120, 220, 240V 50/60Hz (120V Usable 110-130V, 60Hz for U.S.A. & Canada only)
POWER CONSUMPTION: Maximum consumption: 650 watts, Rated consumption: 435 watts (530VA)
DEMENSIONS: 540mm (21-5/16") W x 182mm (7-3/16") H x 397mm (15-11/16") D
WEIGHT: 23.6kg (52.0 lbs) net, 26.0kg (57.3 lbs) packed

*The word "Dolby" and the double-D symbol are trademarks of Dolby Laboratories Inc.
*Noise reduction circuit made under license from Dolby Laboratories Inc.

*Design and specifications subject to change without notice for improvements.

2. BLOCK DIAGRAM

2-1. Audio Section

A block diagram illustrating the audio signal path, including tone control, microphone amplifier, protector circuit, and power amplifier.

2-2. Tuner Section

A block diagram showing the tuner section, encompassing FM and AM tuners, IF stages, discriminator, MPX PLL IC, and various meters.

2-3. Dolby Mode Section

Detailed diagrams for the Dolby FM and Dolby NR selector operations, showing signal flow for playback and recording.

3. OPERATION OF DOLBY FM SYSTEM

This Dolby Noise Reduction System Type B enhances the Signal-to-Noise (S/N) ratio in FM stereophonic broadcasts, improving audio performance. The system utilizes an IC NE545B for the main Dolby circuit. Key operational principles include a 25μs de-emphasis for FM-out, specific input levels for Dolby FM, and an internal 400Hz oscillator for Dolby Tone adjustment.

Principles: The S/N ratio in FM is affected by frequency and signal level. The system expands the middle and high range of low-level signals, which are then compressed proportionally by the receiver. The operating diagram is shown in Fig. 3-3.

Complementary items:

• When Dolby FM system is used, the de-emphasis of FM-out is 25μs.
• The input level of Dolby FM is at 50% modulation and ±37.5kHz.
• The unit has an own 400Hz Oscillator for Dolby Tone in order to adjust itself to the Dolby level.

4. ADJUSTMENTS

4-1. Dolby Circuit Adjustment

4-1-1. Input Level Adjustment of Dolby IC (NE545B)

This procedure involves adjusting specific volume controls (VR01, VR02) using a VTVM to achieve a specified output level from the REC Terminal.

4-1-2. Calibration Tone Volume & Dolby Meter Volume Adjustment

This adjustment requires setting the Master Volume to minimum, connecting a VTVM to the front TAPE I REC terminal, and adjusting VR601 on the F-2655 circuit board to obtain 270mV. Subsequently, VR03 (L-CH) and VR04 (R-CH) are adjusted so the power meter indicator centers on the Dolby mark.

4-1-3. Dolby FM Volume Adjustment

This involves setting the selector to FM Auto, Dolby Selector to Dolby FM, and REC CAL. TONE Switch to OFF. The Master Volume is set to minimum. The adjustment is performed by setting the FM SSG output to specific levels and adjusting VR03 on the F-2654 circuit board to achieve the specified output level.

4-2. Adjustment of Audio Section

4-2-1. Power Meter Adjustment

The unit should be run for at least 4 minutes before adjustment. The procedure involves connecting a DC volt meter to the Speaker Terminals (L-CH and R-CH) and adjusting VR01 and VR02 on the F-2657 circuit board to set the meter position to 50W.

4-3. Adjustment of Tuner Section

4-3-1. FM Adjustment & Alignment

This section details the FM adjustment and alignment procedures using a Genescope and FM SSG. It involves connecting the Genescope output to specific test points (TP) and adjusting various coils and potentiometers (e.g., IF Coil, Muting Coil, Discriminator Coil, RF Adj., Signal Meter Volume, Distortion, Tune Meter Volume) to achieve optimal performance. The procedure includes specific frequency settings and measurement outputs.

4-3-2. AM IF Adjustment & Tracking

This procedure outlines the steps for adjusting and tracking the AM IF section, involving similar equipment and measurement techniques as the FM section, but focused on AM frequencies.

5. PARTS LOCATION AND PARTS LIST

This section provides detailed diagrams showing the location of components on various circuit boards (F-2549, F-2627, F-1519, F-2653, F-2624, F-2544, F-2617, F-2619, F-2657, F-2656, F-2684, F-2682, F-2683, F-2692, F-2695, F-2654, F-2655, F-2623, F-2693, F-2694, F-2690) along with their corresponding parts lists, including stock numbers, descriptions, and positions.

6. OTHER PARTS

6-1. Top Side

Diagram showing the top side layout of components and their connections, including voltage selector, thermal read switch, antenna, and various circuit boards.

6-2. Bottom Side

Diagram illustrating the bottom side layout of components, including input terminals, speaker terminals, power cord, and circuit boards.

6-3. Exploded View

An exploded view of the receiver, showing the assembly of all major parts and components.

7. SCHEMATIC DIAGRAM

Detailed schematic diagrams are provided for the Tuner Section, Audio Section (for both 8080DB/890DB and 9090DB/990DB models), illustrating the electronic circuitry.

8. THREADING OF DIAL CORD

8-1. Threading of Dial Cord

Instructions and diagrams for correctly threading the dial cord, including procedures for replacement if the cord is cut or slips. The dial cord length is approximately 155cm (63 inches).

8-2. Attachment of Dial Pointer

Guidance on attaching the dial pointer, ensuring it is set to the 0 position on the dial scale and moves smoothly when the tuning shaft is turned.

9. PACKING LIST

A list of packing materials used for the product, including vinyl cover, styrofoam packing, and carton cases.

10. ACCESSORY PARTS LIST

A list of included accessory parts, such as Operating Instructions and Schematic Diagrams for different models.