The Marantz 1050 is a classic stereo receiver from the 1970s featuring 50 watts per channel, high-quality analog components, FM/AM tuner, phono input, tape monitor, loudness control, and distinctive Marantz styling. This service manual provides comprehensive technical information for repair, maintenance, and troubleshooting of the Marantz 1050 receiver. Below are key sections for specifications, circuit descriptions, alignment procedures, parts list, and service adjustments.
Complete electrical and mechanical specifications for the Marantz 1050 stereo receiver.
| Parameter | Specification |
|---|---|
| Power Output | 50 watts per channel (8 ohms, 20Hz-20kHz) |
| Total Harmonic Distortion | 0.1% at rated output |
| Frequency Response | 10Hz-50kHz (+0, -1dB) |
| Input Sensitivity | Phono: 2.5mV; Aux: 250mV |
| Signal-to-Noise Ratio | Phono: 75dB; Aux: 90dB |
| Tuner Section | FM/AM with multiplex stereo |
| Dimensions | 17-1/2" W x 5-3/4" H x 14-1/2" D |
| Weight | 26.5 lbs (12 kg) |
| Power Requirements | 120V AC, 60Hz, 280 watts |
| Speaker Impedance | 4-16 ohms |
Detailed block diagram and circuit analysis of all major sections.
WARNING! High voltages present - discharge capacitors before servicing.
Step-by-step disassembly procedure for accessing internal components.
CAUTION! Handle glass tuning dial carefully to avoid breakage.
FM/AM tuner alignment instructions with required test equipment.
DC voltage measurements at key test points with schematic references.
| Test Point | Expected Voltage | Tolerance |
|---|---|---|
| Power Supply Output | +42V DC | ±2V |
| Driver Stage | +35V DC | ±1.5V |
| Preamp Supply | +24V DC | ±1V |
| Output Transistor Base | +0.6V DC | ±0.1V |
| Tuner Supply | +12V DC | ±0.5V |
Complete parts list with Marantz part numbers and equivalent replacements.
Main Components: Output transistors (2SC1116), driver transistors (2SA726/2SC1316), power transformer (P-800), filter capacitors (10,000μF/50V).
Schematics: Full schematic diagrams for amplifier, preamplifier, power supply, and tuner sections with component values and test points.
Recommended replacement transistors for obsolete original components.
| Original Part | Recommended Replacement | Notes |
|---|---|---|
| 2SC1116 (Output) | MJ21193/MJ21194 | Use thermal compound |
| 2SA726/2SC1316 | KSA992/KSC1845 | Driver transistors |
| 2SC458 | KSC1845 | General purpose |
| 2SA561 | KSA992 | Small signal PNP |
| 2SC1345 | KSC1845 | FM RF amplifier |
Detailed service information for the power supply circuit.
Tip: Always replace filter capacitors in pairs for balanced performance.
FM/AM tuner troubleshooting and repair procedures.
WARNING! Use plastic alignment tools to avoid detuning.
Amplifier circuit service and bias adjustment procedures.
Bias Adjustment: Set idle current to 20mA using test points on driver board. DC Offset: Adjust for 0V DC at speaker outputs. Protection Circuit: Test relay operation and DC detection circuit.
Common problems and solutions for the Marantz 1050.
| Symptom | Possible Cause | Corrective Action |
|---|---|---|
| No power | Blown fuse, power switch | Check main fuse F001; test power switch |
| Distorted audio | Output transistors, bias | Test output devices; adjust bias current |
| No FM reception | Tuner section, power supply | Check +12V to tuner; test RF stages |
| One channel dead | Protection relay, amplifier | Check relay contacts; test channel components |
| Hum/buzz | Filter capacitors, grounding | Replace main filters; check ground connections |
Service Notes: Use original Marantz parts when available for authentic performance.
Support: For technical assistance, contact authorized Marantz service centers.