Marantz ST-17 Service Manual

The Marantz ST-17 is a high-performance stereo tuner featuring quartz PLL synthesized tuning, 30 station presets, auto/manual tuning modes, signal strength meter, stereo indicator, RDS (Radio Data System) functionality, and multiple audio outputs. Designed for audiophile-grade reception with advanced noise reduction and selective circuitry. Below are key sections for technical specifications, circuit diagrams, alignment procedures, troubleshooting, and service adjustments.

1. Technical Specifications 2. Block Diagram Overview 3. Circuit Descriptions 4. Alignment Procedures 5. Test Points & Measurements 6. Disassembly Instructions 7. Troubleshooting Guide 8. Parts List & Replacements 9. PCB Layout Diagrams 10. Service Precautions 11. Factory Reset Procedures

Technical Specifications

Key performance parameters: FM tuner section, audio characteristics, power requirements, and physical dimensions.

Parameter	Specification
Tuning Range	87.5 - 108 MHz (FM)
Usable Sensitivity	10.3 dBf (1.0 μV/75Ω)
Signal-to-Noise Ratio	90 dB (Stereo)
Total Harmonic Distortion	0.1% (Mono), 0.2% (Stereo)
Capture Ratio	1.0 dB
Selectivity	80 dB
Image Rejection	90 dB
Power Requirements	120V AC, 60Hz, 15W
Dimensions (W x H x D)	440 x 105 x 340 mm
Weight	4.5 kg

Block Diagram Overview

System architecture showing signal flow from RF input to audio output stages.

RF Amplifier Stage: Initial signal amplification and filtering
Mixer/Oscillator: Frequency conversion to 10.7 MHz IF
IF Amplifier: Multi-stage ceramic filter amplification
FM Detector: Quadrature detector circuit
MPX Decoder: Stereo demodulation and separation
Audio Output: Buffer and line driver stages
Microprocessor Control: Tuning, display, and memory functions

WARNING! High voltages present in power supply section. Disconnect power before servicing.

Circuit Descriptions

Detailed explanation of major circuit sections and their operation.

Tuner Section: Varactor diode tuning with PLL control
IF Amplifier: 3-stage amplification with 10.7 MHz filters
Stereo Decoder: IC-based MPX decoding with 38 kHz regeneration
Power Supply: Linear regulated ±12V and +5V outputs
Display Driver: Fluorescent display with microprocessor control
Memory Circuit: Non-volatile storage for station presets

CAUTION! Static-sensitive components present. Use proper grounding during service.

Alignment Procedures

FM Front End: Adjust RF coils for maximum sensitivity at 98 MHz
IF Alignment: Set detector for minimum distortion at 10.7 MHz
Stereo Decoder: Adjust 19 kHz pilot carrier and 38 kHz subcarrier
Meter Calibration: Set signal strength meter for accurate readings
Oscillator Frequency: Verify PLL reference oscillator accuracy
Required Equipment: FM signal generator, oscilloscope, distortion analyzer
Test Conditions: Standard temperature and humidity environment

Test Points & Measurements

Location and expected values at key test points throughout the circuit.

TP1 (RF Input): Verify proper antenna impedance matching. TP2 (Mixer Output): Check 10.7 MHz IF signal level. TP3 (Detector Output): Monitor audio signal quality. TP4 (MPX Output): Verify stereo separation. TP5 (+12V): Check power supply regulation. TP6 (+5V): Verify logic supply voltage.

Disassembly Instructions

Step-by-step procedure for accessing internal components.

Disconnect AC power cord from wall outlet
Remove six Phillips screws from rear panel
Slide top cover rearward and lift off
Remove front panel knobs and fasteners
Detach display connector from main board
Lift main chassis from bottom enclosure

Tip: Document cable positions and orientation before disconnection.

Troubleshooting Guide

Common symptoms, probable causes, and corrective actions.

Symptom	Possible Cause	Corrective Action
No power	Fuse blown, power supply fault	Check F101 (1A); verify transformer output
No reception	Tuner section failure	Check +12V to tuner; verify oscillator operation
Weak sensitivity	RF amplifier fault	Test Q101-Q103; check antenna input circuit
No stereo	MPX decoder issue	Verify 19 kHz pilot; check IC201 voltages
Display problems	Driver circuit failure	Check -30V supply; test display segments
Memory loss	Backup battery dead	Replace BT201 (3V lithium battery)

Parts List & Replacements

Critical components with manufacturer part numbers and substitutes.

Component	Part Number	Description
IC201	LA1235	FM IF Amplifier/Detector
IC202	LA3401	MPX Stereo Decoder
IC301	μPD1715G	Microprocessor
TUNER	ET-563F	FM Tuner Assembly
Q101-Q103	2SC2999	RF Transistors
F101	1A 250V	AC Line Fuse

PCB Layout Diagrams

Component placement and trace routing for main and display boards.

Main Board (AWM-062): Shows component locations and test points
Display Board (AWM-063): Indicates driver IC and segment connections
Power Supply Section: Highlights high-voltage areas and heat sinks
Tuner Module: Internal component layout and adjustment points

WARNING! Observe polarity when replacing electrolytic capacitors.

Service Precautions

Safety guidelines and special handling requirements.

Always disconnect AC power before servicing. Use isolation transformer when testing live circuits. Observe ESD precautions with MOS devices. Note that some adjustments may affect multiple functions. Record original positions before adjusting coils or transformers.

CAUTION! High voltages present in power supply. Allow capacitors to discharge before handling.

Factory Reset Procedures

Methods for restoring unit to original factory settings.

Function	Reset Procedure
Preset Memory	Hold MEMORY + POWER for 5 seconds
Microprocessor	Remove AC power for 30 minutes
Tuning Offset	Service menu option 07 (technician only)
Display Settings	Reset dimmer and contrast to factory defaults

Service Contacts: Marantz Service Department: 1-800-654-6633; www.marantz.com/service