Kenwood KD-500 / KD-550 Turntable Motor Service

I’m sure every regular visitor to my site knows just how much I love the old Kenwood KD synthetic composite turntables, especially the KD-600/650 series. But the classic Kenwood KD-500/550 is far more common and so I’ve written an article about servicing their direct-drive motors, for anyone who can’t get their deck into me for service, or who just wants to do it themselves.

The Kenwood KD-500/550 turntables utilise a powerful brushless, slotless direct drive motor that spins the platter directly – no belts, pulleys or gears are used, hence the term ‘direct-drive’. These motors are so well-built and so over-engineered that they are usually still going strong, 40+ years after the decks were made. This does not mean that they don’t need maintenance however.

My belief is that the engineers who designed these turntables never envisaged that they would still be in use, let alone running so well and be in demand all these years later. As a result, service documentation typically lists the motors as being sealed for life and not requiring any service. The reality is that, after 40+ years of use, these motors definitely DO need service! I’ve written lots about these Kenwood decks elsewhere on my site, so have a read of some of these other articles, like this one, or check the Liquid Audio KD-500 archives!

Motor services like this is are very common jobs for me. In fact, a large proportion of the work I do is on direct-drive decks like this Kenwood KD-500, fitted with a lovely SME-3009, a wonderful combination. For this service, I attended to the whole deck of course, but here we will focus on just the motor itself. After a proper service like this, and the addition of a high quality synthetic bearing oil – like Liquid Audio bearing oil which I will soon be selling on my site – you will have a quieter, smoother sounding deck, with better imaging and more relaxed presentation. It really makes a difference and is well worth doing every 3 – 5 years.

Typically dirty and well-used KD-500 here. All the grime will soon be gone, but lets focus on that big motor, in the middle!
After removing the rubber mat, gently and evenly lift the platter, jerking it upwards to break the seal developed over time. The top plastic cover needs to next be removed. This involves removing a few small screws, just keep them somewhere safe. Once you have the cover off, you will see the rotor, spindle and FG disc which generates the signal monitored by the deck to keep a constant speed. The frequency of the generated signal is directly proportional to the speed of rotation…
Very carefully loosen the post that the FG sensor sits on. Be careful here, this is delicate work, you do not want to break anything at this stage. Once loosened, you can gently move the sensor away from the FG disc and then lift and remove the rotor. Here you can see I have lifted the rotor upwards, past the sensor. Keep going!
This is the view once the rotor is removed, looking down onto the stator and windings that drive the rotor. The bearing well needs to now be very carefully cleaned with a lint-free cotton swab. All traces of old lubricant and residue need to be removed, take your time and use a solvent if necessary.
You can see that this bearing was quite dirty, filled with dried up, oxidised lubricant that was no longer doing its job.
The rotor in all her glory, this also needs to be gently cleaned and should be spotless before reinsertion into the bearing. Take your time and be very gentle with everything, the ferrite magnets are fragile!
After adding just a few drops of synthetic bearing oil, enough to just cover the bottom of the bearing well, you can lower the rotor/spindle assembly back into the motor. You need to make way for the sensor again, and don’t force anything, this may take several hours to settle in a low-tolerance bearing.
This took about an hour to settle to this point. You then need to carefully move the sensor back into position.
You are now almost done – reinstall the plastic cover and reattach the platter. You need to test the deck now. Sometimes, when the sensor is moved as you need to do to service the motor, the speed lock may not work quite right. Don’t panic, you may need to adjust the position of that sensor. This is easily done, just loosen the two screws that hold the base of the sensor post slightly and move the sensor so that, when you look from above, it sits symmetrically and centrally around the slotted FG wheel. Tighten, test again and make any small adjustments that are needed. Enjoy your serviced deck!

4 thoughts on “Kenwood KD-500 / KD-550 Turntable Motor Service”

  1. Wonderful site. Nice to find another appreciator of these great Kenwood machines. I started with a KD-2055 and was hooked.
    I just found two KD-5070 models here in Denver, Colorado. I see that you are focused on the non-automatic models. I get it. However, when fixing the return mechanism on one of mine I loved the ballet mecanique taking place underneath. I’m designing a mirror-box mount to show off the workings.

    1. Hi Nik, thank you very much, very kind of you and glad you like the site! Yes these classic Kenwood decks are very lovable. I agree, the mechanisms in some of these decks are something you have to see working to believe!

  2. The platter on my KD550 moves horizontally ever so slightly. I am worried that the spindle is bent? When I look down on the spindle, with the platter removed, I can see the whole spindle assembly moving side to side. Again, very slightly. Is there a fix for this? Should I ven worry about it?

    1. Hi Chris, unfortunately you definitely should worry about this if you can see the spindle wobbling without the platter. The best way to measure this is with a dial gauge, measuring runout. If the spindle is bent, the deck will never play a record properly, though it will still play them. You need to establish where the bend is, if any, and work from there. There will always be a little movement between the platter and spindle, as they are just an interference fit. regards, Mike.

Thanks for reading, leave a comment and let me know what you think!