Iconic Kenwood KD-650 Turntable Repair & Review

The beautiful and iconic Kenwood KD-650 turntable is one of the very best decks of its era. Come with me as I repair an elusive fault, overhaul and review this classic deck.

It’s no secret that the Kenwood KD-600 is one of my favourite vintage turntables. I’ve owned a KD-600 for many years and this is how she’s currently set up, with Jelco arm, FR cartridge, headshell, and Kenwood TS-10 ceramic platter mat. The Kenwood KD-650 you see here comes factory-fitted with an excellent Kenwood tonearm.

I’ve written about servicing and repairing the KD-600 and 650 before, though this is my most comprehensive article on these decks to date. Before we get further into the article, check out my video covering the overhaul and repair of this deck.

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Few decks look this cool and perform so well to boot.

As mentioned, the Kenwood KD-650 and KD-600 are identical, aside from the aforementioned 10 inch Kenwood tonearm of the 650. The decks feature beautiful, slim styling and an unusual synthetic granite/marble chassis that looks cool even now. I particularly enjoy the way the light coloured chassis contrasts with the black base panel and light blue Kenwood TS-10 ceramic platter mat.

The fact that Kenwood sold a lot of KD-600s and 650s should be of no surprise. Heavyweight build and sound quality, state of the art specifications and high-tech materials combined with a sensible price-tag, created an instant classic for the company. Kenwood utilised high-quality materials that hold up very well over 40+ years. Add all this to excellent reliability and you’ll see why these decks have become almost unobtainable on the used market.

The KD-600 and KD-650 are technically better and better sounding decks than the much-loved KD-500 and KD-550, and original retail and current market prices reflect this. Their rarity and the reluctance of owners to part with them now, means they sell for big money, if you can even find one.

Features

The KD-600 & 650 feature a brushless and slotless direct drive motor, quartz referenced phase-locked speed control, high-inertia machined and balanced aluminium platter and heavy rubber mat.  The S-shaped tonearm is longer than normal, at around 245mm, or nearly 10 inches.

The chassis is made of Kenwood’s proprietary Anti Resonance Compression Base or ARCB synthetic granite / marble material. ARCB spawned many imitators, but this is the original and best. The deck is started and stopped with very cool touch sensors that respond to the lightest touch.

Just like the incredible Sony PS-8750 I wrote about recently, the KD-650 has proper quartz crystal speed control, here with the crystal contained in a thermally insulated box, for maximum accuracy and minimum drift.

Space-age engineering like this contrasts starkly with lightweight chassis, belt-drive, wobbly suspension and clock motors indexed to mains frequency offered by other manufacturers. As if 50Hz is a reference frequency one should use for a turntable! It’s little wonder the market flipped when decks like this, the PS-8750 and the Technics SL-1200 appeared.

Sadly, not much is made like this anymore, because it ends up being just too expensive and sitting on store shelves. One of the only modern equivalents is Technics’ SL-1200GR, a lovely deck, though not as good as a KD-600 / 650 and selling for a cool $5000 AUD, with a nice cartridge, from a reputable dealer!

Specifications, courtesy of Vinyl Engine

Have a good look at these specs, because they are state of the art, even now. The 600 / 650 hailed from an era when these machines were the pinnacle of hi-fi audio reproduction. Wow & flutter of 0.025% WRMS is a superb spec. Most ultra expensive new decks can’t beat this, except maybe the stunning Technics SP-10R. If pitch stability matters to you, and it should, look closely at decks like these.

Drive: quartz PLL direct-drive system
Motor: 20-pole 30 slot brushless DC servo motor
Platter: 33cm, 2.6kg aluminium alloy die-cast
Speeds: 33.33 and 45rpm
Wow & flutter: less than 0.025% WRMS!
Signal to noise ratio: more than -75dB
Tonearm: static-balance type, s-shaped pipe arm
Effective length: 245mm
Overhang: 15mm
Stylus pressure range: 0 to 3g
Usable cartridge range: 2 to 12g
Dimensions: 490 x 165 x 460mm
Weight: 15.4kg!
Year: 1978 – 1981

Problems

My customer bought his Kenwood KD-650 for a very fair price, but it came with a critical fault. An electronics repairer owned it for years and had not been able to get this KD-650 to spin. It powered on, but was completely unresponsive to the touch sensor. It turned out that one of the CMOS logic chips was broken and finding this fault was very satisfying.

In addition to a repair, the deck needed my standard KD-600 / 650 service including touch sensor deep clean, which I now do on all these decks. After completing other service elements, a KD-600 / 650 should be carefully set-up and adjusted, using an oscilloscope and digital multimeter. There is no shortcutting this process, so let’s go!

Overhaul

First steps involve servicing the switch and replacing some capacitors. As I often explain, the original capacitors were fine, but my customer requested I replace them as part of this overhaul, a perfectly reasonable request.

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Here’s the KD-650, with the base removed. Note the brace between tonearm and motor, moulded into the ARCB material. Note also the well laid out two board design. this is one of the most serviceable decks I’ve had the pleasure of working on.
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Control and motor drive board. Rectangular black box middle top is the temperature stabilised quartz crystal.
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Here I am about to service the speed control touch sensor. I’ve developed a process to service these switches that eliminates some of the operational issues that arise as they get older.
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New high-spec capacitors all round.

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Repair

Time now to find and fix this weird deck control issue.

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Refurbished board back in place, it’s now time to troubleshoot the logic issue…
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The service manual is essential…
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The video I made on this shows this part in more detail, but I traced the fault to a faulty logic gate, within one chip. It was a broken OR gate that prevented the deck start command from being executed.
img_2313 Iconic Kenwood KD-650 Turntable Repair & Review
This is that chip, a CD4001BE, the replacement in this case. When a logic chip fails in some way, part of what you expect to happen (the logic) does not happen. The trick is to find out where the logic fails (eg 2 + 2 = 5). Once that is done, the chip can be replaced.
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And here, after some final touches to the top traces. It’s not strictly necessary to solder these top traces as the pads are through-hole plated.
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Anyway, just because I was excited, here is the finished and repaired board!

Motor Service & Control Circuit Adjustments

Next step in the overhaul of a KD-600 / 650 involves a bunch of adjustments. Don’t be tempted to ‘twiddle’ trimmers if you don’t know what you are doing or you’ll end up with a deck that doesn’t work. A dual channel oscilloscope, probes and an accurate multimeter are needed for these next steps.

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Deck ready for motor service

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Removing the cover reveals the rotor assembly
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And this is what you are paying for, this is a serious direct-drive motor, and bearing.
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Careful extraction of the rotor reveals a many pole motor stator. The large number of poles partially explains the extraordinary wow and flutter specs of the KD-600 and 650. Nobody was asleep when they specced designed this motor.
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This is the bearing well, after cleaning. Next step involves adding a small quantity of synthetic bearing oil…
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Followed by reinsertion of the rotor assembly. Even the slightest bit of lint caught in this tight tolerance bearing will prevent or impede the rotor sinking back into place. Ordinarily, this should take a few minutes.
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Final electronic adjustments take time and need a precision multimeter and dual channel scope, like my Tektronix you see in the background. Astute readers will note I’ve supported the deck on blocks for this stage of the service. That allows access to the underside whilst the deck is running. This work is tedious but critical and involves adjustment of speed, phase-locked loop and electronic braking. My video has more on this.

Cartridge Installation & Set-up

Second last step involves installation of a new cartridge, and carefully setting overhang, azimuth, tracking force, anti-skate and ride height.

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Removal of the old Audio Technica cart. Note the very nice, original Kenwood headshell.
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This is a retipped Fidelity Research FR-1 Mk3. These are superb cartridges and I am now able to offer retipping advice and service, should you need it.
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Lovely straight cantilever, aluminium tube design of course, like the original, with nude-mounted gem. This is what I would recommend on other FR-1s.
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I’ve mounted the FR-1 with a new set of hardware of precisely the right dimensions. I have most sizes here in stock.

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All done, note the nice Litz wiring of the Kenwood headshell.

Cleaning & Finishing Touches

I always thoroughly clean equipment that visits the Liquid Audio workshop as a part of the service.

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There was a layer of grime over the deck, but it came off easily.

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Lid also receives a deep clean and shortly thereafter, a polish.

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Much better. Notice the arm height adjustment here.

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I’ve added some new, clear lid bump stops. These little touches make all the difference I think.
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Buffing up the lid with a plastic polishing compound.
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And voila!

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What a stunning looking turntable. Just as well these perform as fantastically as they look!

Sound Quality & Bottom Line

A high-quality direct drive deck like this will always sound good, especially in terms of pitch and timbral accuracy. Add in the superb chassis, platter, motor and tonearm you get with the KD-650 and you have a real heavy hitter. Even the lid is one of the thickest and heaviest available.

The over-engineered motor provides vanishingly low wow & flutter and very low rumble. This lowers the noise floor, enhances dynamics and improves realism with acoustic instruments. The longer tonearm lowers tracking distortion when compared with regular 9 inch arms.

Seriously, nothing new for sensible money can touch the performance of a well set up KD-600 or KD-650, especially not with an FR-1 or similar high-performance cartridge. For example, the KD-650 is definitely a better turntable than Technics’ new SL-1200GR, and that sells for $5000 AUD

This is 15kg of pure, unadulterated Japanese engineering, the sort that makes other manufacturers who can’t build arm height adjustment into their decks say “arm height adjustment isn’t important.” Yeah right!

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So, if you’re looking for an amazing vintage deck, or are perhaps stepping up from a belt drive or lesser direct drive and don’t have the many thousands of dollars needed to attain this level of performance in a new deck, I strongly suggest a Kenwood KD-600 or KD-650.

Of course, if you’d like Liquid Audio to repair or service your KD-600 or KD-650, you need only contact me to book an appointment.

Kenwood KD-650

$750 - $1500 AUD
9.1

Chassis / Build-Quality

9.5/10

Features

8.5/10

Sound Quality

9.0/10

Scalability

9.0/10

Bang-Per-Buck

9.5/10

Pros

  • Heavyweight construction
  • First class sound quality
  • Excellent servicability
  • Long, adjustable tonearm
  • Minimalist styling

Cons

  • High secondhand prices
  • Lid hinges can fail

2 thoughts on “Iconic Kenwood KD-650 Turntable Repair & Review”

  1. Awesome! I myself have a KD 600 & 650 due to Mike’s previous posts about them & can testify to the absolute truth of his remarks on their amazing sound quality. I had been a vinyl enthusiast for 40+ years prior to obtaining the Kenwood decks & they are hands down the single biggest upgrade to my record listening experience. It fills me with joy to see that yet another of these vintage decks will still be going strong after all these years. Thanks again Mike for being a beacon in the darkness for vintage audio enthusiasts everywhere!!

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