Luxman L-590AXII Integrated Amplifier Repair Guide

Model Overview

The Luxman L-590AXII is the flagship pure Class A integrated amplifier representing the absolute pinnacle of Luxman's audio engineering. This second-generation model features enhanced power supply regulation, improved thermal management, and higher power output compared to the original L-590AX. With 30 watts per channel of pure Class A power into 8 ohms, this amplifier delivers exceptional sonic performance with Luxman's renowned musicality, detail retrieval, and authoritative control.

Common Issues and Solutions

Power Supply Problems

The L-590AXII power supply can develop specific issues due to extreme Class A operation:

• Capacitor failure: Extreme high-temperature operation accelerates capacitor aging dramatically
• Rectifier issues: Very high-current rectifiers can fail under continuous heavy load
• Transformer stress: Massive power transformer may develop issues under continuous high load
• Voltage regulator failure: Regulator circuits heavily stressed by high current demands
• Thermal stress: Extreme continuous high temperatures affect all component lifespans
• Soft-start circuit failure: High inrush current stresses soft-start components

Class A Output Stage Problems

Specific to high-power Class A amplifier issues:

• Bias current drift: Critical bias settings can drift significantly over time
• Thermal runaway: Output transistors may overheat without precise bias control
• Output transistor failure: Power devices heavily stressed by continuous high-current operation
• Heat sink issues: Massive heat sinks may develop thermal interface problems
• DC offset problems: Critical for speaker protection in high-power design
• Current mirror issues: Precision current sources may drift

Preamplifier Section Problems

The sophisticated preamplifier section can develop issues:

• Potentiometer noise: High-quality volume/control pots may develop noise
• Selector switch issues: Complex input selection system problems
• Phono stage problems: Issues with the high-quality MM/MC phono input
• Balance control problems: Precision balance control issues
• Buffer stage issues: Problems with the high-current buffer amplifiers

Thermal Management Issues

Critical for high-power Class A operation:

• Thermal compound degradation: Dried thermal interface material on massive heat sinks
• Heat sink corrosion: Large aluminum heat sink oxidation
• Temperature sensor failure: Sophisticated protection circuit malfunctions
• Ventilation issues: Blocked ventilation paths causing overheating
• Thermal stress cracks: PCB damage from repeated thermal cycling

Capacitor Replacement Guide

The following capacitors should be replaced in any comprehensive restoration. Use only high-temperature, audio-grade components:

Critical Components to Check/Replace

Component	Reference	Location	Notes
Output Transistors	Q101-Q108	Amplifier Board	Multiple parallel devices - must be matched sets
Driver Transistors	Q201-Q208	Amplifier Board	High-current drivers - check for thermal stress
Bias Transistors	Q301-Q304	Amplifier Board	Critical for Class A bias stability - precision parts
Voltage Regulators	IC101-IC104	Power Supply	Multiple high-current regulators
Protection Relay	RLY101, RLY102	Protection Board	High-current relays - check for contact oxidation
Power Resistors	R101-R112	Power Supply/Amplifier	High-wattage resistors - check for overheating
Thermal Sensors	TH101-TH104	Heat Sinks	Multiple temperature sensors for protection

Restoration Procedure

1. Disconnect power and allow unit to cool completely (minimum 4 hours)
2. Discharge all capacitors completely - this unit stores significant energy
3. Document all wiring with high-resolution photos before disassembly
4. Replace all electrolytic capacitors with 105°C high-temperature rated equivalents
5. Check and replace out-of-spec resistors, especially in critical bias circuits
6. Clean all controls and switches with high-quality contact cleaner
7. Check output transistors and replace if necessary with carefully matched sets
8. Check driver transistors and replace if necessary with precision parts
9. Clean protection relay contacts or replace if pitted
10. Reapply high-quality thermal compound to all power devices
11. Clean massive heat sinks and check for proper thermal transfer
12. Inspect PCBs for thermal stress cracks and repair if necessary
13. Reassemble and power up slowly using a variac over 2-3 minutes
14. Adjust bias and DC offset according to service manual specifications
15. Monitor temperatures carefully during extended operation

Calibration Procedure

After restoration, these precise calibrations are essential for proper high-power Class A operation:

• Set DC offset to zero (adjust VR101, VR102) - critical precision
• Adjust Class A bias current precisely (adjust VR103, VR104) - allow 45-minute warm-up
• Verify balance between parallel output devices
• Check and adjust current mirror circuits if accessible
• Verify proper operation of sophisticated thermal protection circuit
• Check phono stage gain and RIAA equalization accuracy
• Verify proper operation of all inputs and controls
• Monitor heat sink temperatures during extended operation (should stabilize below 65°C)
• Verify proper operation of protection circuits under load

Additional Tips

• Use only highest quality 105°C rated capacitors from reputable manufacturers
• Consider using silver-based thermal compound for better heat transfer
• Allow ample warm-up time (45+ minutes) before making final bias adjustments
• Use thermal imaging camera to verify even heat distribution across heat sinks
• Clean all controls thoroughly with Deoxit Gold for best performance
• Ensure adequate ventilation - minimum 30cm clearance on all sides
• Monitor bias current stability over 24-hour period
• Use precisely matched transistor sets when replacing output devices
• Consider upgrading binding posts to highest quality alternatives
• Keep service manual handy for specific adjustment procedures