Marantz Model 18 Manual

The Marantz Model 18 is a classic stereo receiver from the golden age of hi-fi, featuring vacuum tube amplification, FM/AM tuner capabilities, high-quality audio components, and the distinctive Marantz blue-lit tuning eye. This manual covers operation, specifications, connections, maintenance, and troubleshooting for this vintage audio masterpiece.

Features at a Glance

Key components: Vacuum tube amplifier section, FM/AM tuner, Tuning meter, Speaker outputs, Multiple input options.

Feature	Description
Power Output	35 watts per channel RMS
Tuner Section	FM/AM with tuning meter
Inputs	Phono, Aux, Tape Monitor
Outputs	Speaker A/B, Tape Out
Tubes	7591 output tubes, 12AX7 preamp tubes
Tuning Eye	Blue fluorescent tuning indicator
Loudness Control	Compensates for low-volume listening
Tone Controls	Bass and treble adjustment
Filter Switches	High and low frequency filters
Power Switch	Main power on/off with indicator light

Installation

Unpack carefully and inspect for damage. Place on stable, level surface with adequate ventilation.

1. Connect speakers: Use proper gauge speaker wire to A or B speaker terminals.
2. Connect turntable: Use phono input for magnetic cartridges.
3. Connect other sources: Use Aux input for CD players, tape decks, etc.
4. Connect antenna: FM antenna to 300 ohm terminals, AM antenna to AM terminal.
5. Plug into AC power outlet.

WARNING! Tubes generate significant heat; ensure adequate ventilation space around unit.

First-Time Setup

Allow unit to warm up for proper operation.

1. Power on: Turn power switch; allow 30 seconds for tubes to warm up.
2. Select input: Choose Phono, Aux, or Tuner as needed.
3. Tune FM/AM: Use tuning knob and watch tuning meter for strongest signal.
4. Adjust volume: Start at minimum, gradually increase to desired level.
5. Set tone controls: Adjust bass and treble to preference.

CAUTION! Do not touch tubes during operation - they become extremely hot.

Specifications

• Power Output: 35 watts per channel RMS
• Frequency Response: 20Hz - 20kHz ±1dB
• Total Harmonic Distortion: Less than 0.5% at rated power
• Input Sensitivity: Phono: 2.5mV, Aux: 250mV
• Signal-to-Noise Ratio: Phono: 65dB, Aux: 75dB
• Tuner Section: FM/AM with multiplex stereo
• Tubes: 4x 7591 output, 4x 12AX7, 1x 6AU6, 2x 6BA6, etc.
• Power Requirements: 117V AC, 60Hz, 200 watts
• Dimensions: 16" W x 5.5" H x 14" D
• Weight: 35 lbs

Controls and Settings

Front panel controls: Power switch, Input selector, Volume, Balance, Bass, Treble, Loudness, Filter switches, Tuning knob, Function selector.

Rear Panel: Speaker terminals, Input jacks, Antenna terminals, AC power cord, Fuse holder.

Input Selection: Phono (magnetic), Aux, Tuner. Tone Controls: Bass ±12dB at 50Hz, Treble ±12dB at 10kHz. Filters: High cut and low cut for noise reduction. Loudness: Compensates for Fletcher-Munson curve at low volumes.

Connecting Components

Speaker connections: Use A or B speaker terminals with proper polarity. Source connections: Phono for turntable, Aux for other line-level sources.

1. Turn off power before making connections.
2. Connect speakers ensuring positive/negative polarity.
3. Connect turntable ground wire to ground terminal.
4. Use quality interconnects for source components.
5. Connect FM dipole antenna for best reception.

Tip: Keep signal cables away from power cords to minimize hum.

Tuner Operation

FM/AM tuning with stereo capability.

1. Select Tuner on input selector.
2. Adjust tuning knob while watching tuning meter.
3. Center tuning for strongest signal and minimum distortion.
4. For FM stereo, ensure stereo indicator is lit.
5. Use AFC (Automatic Frequency Control) for stable reception.
6. Adjust antenna for best signal strength.
7. Use high filter to reduce FM hiss if needed.

WARNING! Do not operate without proper load (speakers connected).

Maintenance

Regular maintenance ensures optimal performance and longevity.

1. Tube replacement: Replace output tubes every 2-3 years with matched sets.
2. Bias adjustment: Have qualified technician adjust bias periodically.
3. Cleaning: Use soft cloth for exterior; compressed air for dust removal.
4. Ventilation: Ensure adequate airflow around unit.
5. Fuse replacement: Use only specified fuse rating.

CAUTION! High voltages present - refer servicing to qualified personnel.

Safety Information

This unit contains lethal voltages. Always unplug before servicing.

• Do not remove covers - no user-serviceable parts inside
• Ensure proper ventilation - minimum 4 inches clearance on all sides
• Use correct fuse rating - 3AG 2.5A slow-blow
• Keep away from moisture and extreme temperatures
• Do not block ventilation slots

Technical Data

Circuit design: Push-pull ultra-linear output stage. Transformers: High-quality output transformers for wide bandwidth. Power supply: Solid-state rectification with tube regulation. Protection: Fuse protection for output tubes and power transformer.

Tube Complement: 4x 7591 (output), 4x 12AX7 (preamp/phase splitter), 1x 6AU6 (FM RF), 2x 6BA6 (FM IF), 1x 6BE6 (FM mixer), 1x 6AL5 (FM detector), 1x 6CG8 (FM multiplex)

Troubleshooting

Symptom	Possible Cause	Corrective Action
No sound	Speaker connections/tubes	Check speaker wires; verify tubes are lit; check fuse
Hum or noise	Grounding/tubes	Check turntable ground; tube microphonics; source connections
Weak output	Tubes aging	Replace output tubes; check bias settings
Poor FM reception	Antenna/tuning	Adjust antenna; check antenna connections; fine tune
Overheating	Ventilation/bias	Ensure adequate ventilation; check bias current

Service: Refer to qualified Marantz service technician for all internal repairs.

Note: This vintage equipment may require specialized knowledge for proper maintenance.