Luxman SQ-202 Integrated Amplifier Repair & Service

I get to work on some beautiful gear at Liquid Audio. A great example is this stunning Luxman SQ-202 integrated amplifier that I’ve just repaired and serviced.

The Luxman SQ-202 integrated amplifier is a model dating right back to the early 70’s. In fact it was released 1970, and produced until 1973.

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Classic, understated early Luxman styling. There’s almost a deco tone to the way they used to design their equipment, very different.

Lots more great information and specifications are located at the Vintage Knob page for the SQ-202.

Abbreviated specifications, courtesy of this page with more info on the SQ-202:

Main Amp
Output Power:   70 watts RMS 8 ohms, both channels driven; 80 watts RMS, 8 Ohms, single channel driven; 100 Watts RMS, 4 Ohms, single channel driven.
Frequency Response: 10Hz – 60kHz, -1dB
THD:  Below 0.04%, 8 Ohm, 1 k Hz;  Below 0.05%, 4 Ohm, 1 Khz
Input impedance:  About 100k Ohms
Residual noise:   About 1 mv
Damping Factor:   35, at 8 Ohms

Pre-Amp
Maximum output Voltage:  aprox 5 V
Output Impedance:   Pre Out 100 ohm; Tape out 100 ohm
Frequency response:  20~70KHz within -1db THD
Input Impedance:   Phono – 1 50K Ohms Phono – 2 selectable 30K, 50K, 100k ohms. Aux 1, 2, 3 – 100k ohms
Max input voltage:   Phono-1, Phono-2 180 mV Aux-1,3. 5V Aux-2 adjustable level over 5 V
S/N ratio:  Phono-1, Phono-2. 66db, Aux-1,2,3. 80db, A-Weighted
Filters:  High Cut 5KHz, 9KHz.   Low Cut 30Hz, 80Hz

General
Dimensions: 48cm x 28cm x 16.5cm
Weight: 12.5kg
Original List Price: 141,000Y

Service & Repair

I made short video clip about the SQ-202, which you can view on my YouTube channel.

This SQ-202 came to me with only one channel working. Clearly, some investigative and repair work was needed.

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First look at the old girl
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And my first look inside. Note the neat, compartmentalized construction. Note also, the massive power transformer.
Amplifier Modules
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My first job was to remove these amplifier modules. I knew that these would need an overhaul. Its wonderful just how serviceable a lot of older gear like this is. Each module comes out and then comes apart so easily. Someone was really thinking when they designed this part of the SQ-202.
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A closer view of one of the modules. These feature an non-matched pair of NEC output devices. They are mounted on mica thermal pads, using clear thermal grease. This thermal interface should be renewed on all devices and I do this now as a matter of course on better gear like this.
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Other refurbishment work on these modules included replacement of the two small tantalum capacitors and the small aluminium electrolytic just nearby. The other larger aluminium electrolytic capacitors all tested perfectly, and stayed put.
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One of the tantalum capacitors. Tantalum capacitors are electrolytic capacitors, like aluminium types. They have better high frequency performance in many cases, but also a lower tolerance to voltage and a higher ESR as they age.
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This is a finished module, after disassembly, washing, cleaning and drying, small capacitor replacement, one resistor replacement, semiconductor testing, and remounting of output devices.
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Finished modules side by side
Reassembly and Other Work
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Modules back in chassis for testing. I also replaced both output fuses. One was blown, both were of the wrong value.
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Modules fully reinstalled after extended testing and adjustment, new fuses and heat-soaking.
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Another view while I finish a few things off, like replacing the VU meter lamps….
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All four lamps were blown…
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And doesn’t this look better after a new set of bulbs!
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Finished unit in her very attractive and now very clean case
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It’s hard to tell, but the top case is a very thick mild steel panel, finished in thick textured ‘crackle’ paint. Very nice.

3 thoughts on “Luxman SQ-202 Integrated Amplifier Repair & Service”

  1. I have the matching tuner pulled it out had a listen and thought wow! Probably need all the lamps replaced too.Great sound.

  2. Should anyone ever need to repair another one, I have two pieces of the power amp modules NIB. one with the other without molex plug fitted.

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