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Kenwood KD-650 Direct-Drive Turntable Service and Repair

The Kenwood KD-650 is an amazing turntable. It really is one of the very best decks to come out of the 1970’s and 80’s and if you ever get a chance to purchase either the KD-650, with Kenwood tonearm, or the KD-600, usually with an SME series 3, you should go for it.

The KD-650 is one of the best-performing turntables you can own for sensible money. Featuring a superb brushless and slotless direct-drive motor, quartz phase-locked speed control, high-inertia 3 kg machined and balanced aluminium platter and the now iconic ARCB synthetic composite chassis, this is a seriously heavy hitting turntable.

This is literally space age engineering of course, compared to the wobbly ‘pipe and slippers’ belt-drive decks you could buy at the time. No wonder the market was literally torn open when decks like these appeared! According to Kenwood, the deck exhibited the following features:

High inertia platter: 550kg.cm2
Quartz PLL servo speed control
Electronic controlled braking system
Special anti-vibration rubber platter sheet
Integrated high-performance tonearm
ARCB limestone resin concrete base

The unit is also available as the KD-600 which is supplied with two tonearm bases, one designed for the Ortofon AS-212 mkII and the other for the SME 3009 or Infinity Black Widow laboratory reference tonearms.

This particular KD-650  needed some repairs to the speed lock indicator, touch control switches, a motor service and a general tune-up. The deck came up very nicely after having apparently not worked and sat in the shed for many years.

You can read more about the KD-650 at the legendary Vinyl Engine, and I have a few technical tips and discussion below. Specification for this wonderful turntable are as follows:

Specifications:

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 and flutter: less than 0.025% WRMS
Signal to noise ratio: more than -75dB
Tonearm: static-balance type, s-shaped pipe arm, eia plug-in connector
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

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Inside the Deck:

This shot of the insides of the KD-650 is worth further discussion. Top and centre, you will notice the power supply board. I sometimes upgrade this by replacing the single axial electrolytic capacitor with a better quality part, featuring higher capacitance, lower impedance and longer service life.

To the left, we have the mains transformer, which is rubber mounted so that it hangs and rests against soft rubber bushes when the deck is sitting right way up. You want to check that it is free to move and not binding on the rubber mounts, as this transformer is a source of mechanical hum which can be coupled dthrough to the cartridge. The best option would really be to remove the transformer from the chassis and mount it externally.

To the right, we have the control board and Kenwood didn’t skimp here. There are four adjustments, but don’t go fiddling with these unless you have access to a dual channel oscilloscope that you know how to use, and a precision multimeter. Two of the pots set the absolute speed, whilst the other two are involved with the phase locked loop control and electronic braking.

In the middle, you can see the large direct drive motor. Access to the bearing is via the circular metal plate and screws. You will see the rubber gasket protruding from around the edges of the cover plate. This gasket does deteriorate with age. I reworked the mating surfaces of the plate and bottom of the motor to improve the seal on my KD-600. On this deck though, I cleaned out the bearing and added synthetic bearing oil before carefully re-tightening the plate. This will be sufficient on most KD-600/650s.

12 thoughts on “Kenwood KD-650 Direct-Drive Turntable Service and Repair”

  1. Mike, i have my KD-600 (speed switch tempramental) & KD-650 ( speed unstable, established there was a pcb problem rather than IC issues as replacing ICs didn’t solve issue in past) are repaired now…. i finaly found another deck with a good pcb & speed stable. Turns out the defective KD-650 also had a warped flywheel…. having the donor deck to uses as parts means i have 2 great turntables now. They had bearing service, re-capped PSU and a good clean – they run perfectly now. Brendan Purdy at Tisco in Hamilton, NZ did the repairs. I directed him to your webpage & gave him a PDF copy of the service manual but i think repair was straight forward…. having a donor unit helped heaps I’m sure.

    1. Hi Anthony, great news and thanks for sharing. The touch sensors can be quite problematic, I’ve developed a way of refurbishing them which works very well in most cases. At least you have some spare parts now!

      1. I’m a very happy chappy…. awaiting for the platter ring stabiliser to arrive from Ali.

  2. Добрый день Mike!
    Thanks for information on KD-650.
    Forgive for Google the translation into English from Russian.
    Recently I bought KD-650 in a good external shape.
    The problem was that the motor worked at one high speed.
    My friend, the specialist in repair of the PLL radio receivers had no experience with DD as players.
    It found problem MM74C906N. The old chip wasn’t found in Russia. It was received from China by mail. Problems also were to the diode bridge and capacity in power supply unit. Changeover. Regulation. Everything works well. Regulation of the motor should be done in the look collected with a disk (Platter).
    Nikolay
    Moscow, Russia.

    1. Thanks for sharing this information Nikolay, I’m very glad your KD-650 is now running well. I’m listening to Robert Plant’s The Principle of Moments on my KD-600 as we speak!

  3. Hi, I have a KD 650, won’t speed lock – spins very fast, I have had a tech check it – caps OK, replaced the IC’s and its still fast, any other ideas? i live in NZ, how long do you think it would take to assess a turntable and fix this problem? I’m coming to Perth in May for 3-5 days, contemplating lugging it over …….how much do you charge to fix such a problem?

    1. Hi Antony, thanks for making contact. Hard to say what the issue is or estimate a repair cost without seeing the deck first and testing some things. I would likely need more than 3 – 5 days, so I’d suggest lugging her here is also not the best way to go. A capable tech should definitely be able to fix this though, I’d suggest finding someone else over there who can actually diagnose the problem rather tha just changing parts. Is there anyone else there you can try?

      1. Thanks Mike, I just found maybe 2-3 others in Auckland… making enquiries just now. These are great decks, but the number of techs who have experience with them is not so many now…
        thanks for your suggestions,

        regards,

        Anthony

  4. Hi
    i have a Kenwood kd 600 .it taks of and Wild not get the rigth speed. Do you know wath the problem is.

    1. Hi – without wanting to state the obvious, it sounds broken. I would need to get it on the bench to diagnose the cause and solution to the overspeeeding issue.

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