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Luxman SQ-202 Amplifier Repair & Service

A great example of the beautiful gear I get to work on 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 ’70s. In fact, it was released 1970 and produced until 1973.

Luxman SQ-202
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.

Luxman SQ-202 Specifications

Courtesy of Hans who has 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:  approx 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 a 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
Luxman SQ-202
And my first look inside. Note the neat, compartmentalized construction. Note also, the massive power transformer.
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My first job was to remove these amplifier modules. I knew that these would need an overhaul. It’s 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 a 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 the 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 & Other Work

Luxman SQ-202
Modules back in chassis for testing. I also replaced both output fuses. One was blown, both were of the wrong value.
Luxman SQ-202
Modules fully reinstalled after extended testing and adjustment, new fuses and heat-soaking.
Luxman SQ-202
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.

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12 thoughts on “Luxman SQ-202 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.

  3. Jorgina Christensen

    Hi guys, I’ve recently acquired one of these and thought I’d Google it to get a better understanding of it and this seems to be the only page!
    Just wondering, they seem quite scarce.. Any ideas on how much these are worth?
    Thanks

    1. Hi Jorgina, thanks for your question. There are too many variables to be able to say what something like this is worth without inspecting and testing it to start with to determine its condition, looking at where you live and local market factors etc. They are a beautiful amplifier though and would cost thousands to replace with something new that wouldn’t be nearly as well made.

  4. Hello,
    I also have a copy of this amp. The volume/balace control potentiometer should have been replaced, because it was completely destroyed. Unfortunately, I couldn’t find it on the other side of the world (Hungary), so the thing died. Now it came out from the end of the workshop and I thought it should be fixed. My question is, where can I buy this potentiometer?
    Thank you in advance for your answer!
    Merry Christmas!
    Gábor Péter

    1. Hi Gabor and merry Christmas! There are mechanical and electronic considerations when matching replacement parts like potentiometers that make having everything in front of you really helpful. Everything has to be measured and the schematic consulted to assess mechanical and electronic compatibility, knob compatibility, front panel fitment, etc. Unfortunately, without access to the equipment and some time to do that, I cannot recommend anything. If you are not able to match new part/s the easiest way is often to track down a NOS part or pull. Alternatively, a local specialist repairer may be able to assist.

      1. Hello Mike,

        I thought that the SQ202 was made with only one type of potentiometer, that’s why I asked the question.
        Mine is a little different than the amp you serviced, because mine is completely wood paneled, but the front panel is identical to mine. Unfortunately, I only have the amplifier at hand, because I carried the potentiometer around the country at the same time to look for a replacement. Someone who once worked at the Hungarian radio station said that these Alps pots were popularly used in mixing consoles. I shold try to search in this direction.
        But now I don’t know where I put the part. If I have it, I will apply.

        All the best from Hungary
        Gábor

        1. Hi Gabor, yes, I’ve only seen one type of volume pot assembly on these amps, this is not the problem. Most Japanese gear used and uses ALPS pots, but it’s the unique design, ie ganging of volume and balance and all the mechanical dimensions and electronic parameters I mentioned previously that must be known to match something. It will be easier to find a pulled part, as I said, that is likely your best option here.

          1. Hi Mike, so far I have stuck to the original part that was included, but your answer convinced me, so I am looking for a replacement from another brand. Thanks anyway!

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