Kenwood Direct Drive - Oiling the Bearing

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Hugo
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Kenwood Direct Drive - Oiling the Bearing

Post by Hugo » 16 Oct 2009 15:04

I have an old Kenwood KD-770D direct drive deck, which I believe needs some lubrication in its main bearing. The motor block was used in many different Kenwood decks, and is shown here:

https://i155.photobucket.com/albums/s30 ... mplete.jpg

Has anyone dismantled one of these motor blocks to get at the main bearing? I'd be very grateful for any advice, particularly in respect of potential pitfalls.

Many thanks!

nat
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Post by nat » 16 Oct 2009 17:01

Often the spindle is integrated into the rotor of the motor, and you have to figure out how to remove the whole thing. It the motor is on top of the plinth, often there is a decorative cover, but if below, the whole motor must be dropped. On the KD 500 there is a speed sensor that must be loosened and moved out of the way, but otherwise straightforward.
But I don't know the 770 -- have you checked for a service manual?

nat
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Post by nat » 16 Oct 2009 17:33

There is a service manual in the Library, in english, french, and german. Looks like you remove the motor from the bottom but not clear from the picture what to do after that.

Hugo
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Post by Hugo » 16 Oct 2009 18:48

nat wrote:There is a service manual in the Library, in english, french, and german. Looks like you remove the motor from the bottom but not clear from the picture what to do after that.
Yes there is, and I provided it to VE! As you say, it's not particularly clear. I just want some reassurance that some tiny part will not be flung across the room when I take the motor block apart.

Shoji
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Post by Shoji » 16 Oct 2009 19:09

Hello. This series motor design for life and no intention for service. Lubrication from factory is grease base and never designed for replace of lubrication. If motor spindle rotate free and with quiet then all is OK. Not designed for dismantle. No worry about lubrication of this motor. :D

nat
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Post by nat » 21 Oct 2009 01:51

The question I have is what the life of the turntable was expected to be. All mechanical products have some expected service life, and no lubricant is eternal. So its possible that Kenwood never expected that people would be using turntables 40 years after they were built, and that no one actually knows how long those greases will work.
If everything works well, than probably you should leave well enough alone. But absent some reference, how can you tell if everything is working well?

Shoji
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Post by Shoji » 21 Oct 2009 08:24

Hello Nat. Is very good question. Is possible design team give thought to life only in accord with normal program to make available the spare part for period 7 years after manufacture :?: In recent time I look to bearing of motor much like this one discussed and still grease look excellent. This example I look to not have much hours in play so only passing of time have effect. Agree if all working well to leave alone.

Hugo
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Post by Hugo » 22 Oct 2009 07:03

Ad soon as I can find a suitable tool to remove the big nut that holds the bearing housing to the composite motor block, I shall clean the bearing out and try some transmission oil instead. The Kenwood has a relatively low torque motor, and the grease in the bearing is clearly quite 'sticky' as the spindle does not spin very freely; and this may be the reason why there is a 'feeling' of speed instability when listening to music on my deck. If grease turns out to be better, then it's no problem to use that.

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Post by caligari » 01 Nov 2009 04:48

I love this model. It is one of the few top models that use a coreless motor along with the KD-990. It has a smoothness in the sound that rivals the JVC tables. I would say it's my favorite turntable for playing violin music or chamber music. Its sound is so delicate and pretty and it rivals a belt-drive turntable in its fluidity. I look forward to your report on the condition of the bearing. If it needs re-lubricating then I might try that on mine too. The tonearm is amazing quality but unfortunately my unit is missing the stock headshell which is very hard to find. I have to resort to a weird aftermarket headshell that happens to have a pivot but that's sacrificing rigidity so I hope I can find a stock headshell one day. I would love to find a KD-990 one day as its anti-vibrational skeletal construction under the plinth is amazing engineering. Both models use a coreless motor to have that silky smooth sound. I really don't care for the earlier models conventional core motor but I think they got overrated because of their marble plinth construction. Give me a smooth motor anyday! Anyway, look forward to further reports. Thanks for posting the picture.

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Post by Cobra2 » 01 Nov 2009 07:38

I have had KD-700 & KD-990 here, both have same motor.
I did not care too much about them, mostly because of the tone-arm.
And because my SP-10MkII would eat them for breakfast...

Arne K

Hugo
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Post by Hugo » 01 Nov 2009 07:53

The KD-770D bearing is quite a stout, flat ended affair, with a plain greased sleeve. The end of the bearing sits on a small thrust pad, which may be teflon, or just a form of hard plastic. I've cleaned out the grease and lubricated it using some synthetic gear oil, which makes it run a bit more freely than with grease. Now that I know the spindle is held in the motor block by a quite strong magnetic attraction, but nothing else, it will be no trouble to use some grease if that proves necessary. The apparent 'drag' in the bearing seems to be a due to that strong magnetic pull, but it does turn more freely with oil. The bearing sleeve is not sealed, though, so excess oil squirts out of the bottom when the spindle is inserted.

I am impressed by how well designed and engineered the Kenwood motor unit is. Unlike the Technics SL-1200, whose bearing is not particularly firmly attached, the Kenwood's is bolted very firmly to a large corian type block, which in turn is bolted to the turntable chassis, spreading the load very widely. The big nut underneath the motor unit that you can see in the first picture below secures the bearing assembly very firmly to that block.

https://i155.photobucket.com/albums/s30 ... 1-1640.jpg

And here is the spindle assembly:

https://i155.photobucket.com/albums/s30 ... 1-1641.jpg

And the complete motor unit:
https://i155.photobucket.com/albums/s30 ... 1-1640.jpg

Hugo
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Post by Hugo » 01 Nov 2009 07:54

Cobra2 wrote:I have had KD-700 & KD-990 here, both have same motor.
I did not care too much about them, mostly because of the tone-arm.
And because my SP-10MkII would eat them for breakfast...

Arne K
I never used the standard tone-arm, preferring a Michell TecnoarmA. I also have a Jelco SA-750D to try, but I need to make up a suitable arm board.

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Post by Shoji » 01 Nov 2009 09:09

Hello Hugo. Please not to use the oil in this series motor spindle. If must replace original grease look to some thing like NSK NS7 or may be NSK NSA grease. This series motor have no oil seal and not designed for oil. If use oil will have high speep rate and result in increase level wear.

Hugo
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Post by Hugo » 01 Nov 2009 10:29

Shoji, you're right, but I wanted to hear how the KD-770D sounds with oil in the bearing instead of grease. It might be possible to seal the bearing to keep the oil in, though.

Does anyone know where I can get a small quantity of NSK NS7 grease in the UK?

Hugo
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Post by Hugo » 01 Nov 2009 12:00

OK - the Kenwood is now set up with my TecnoarmA and Ortofon Kontrapunkt B cartridge. Immediately, the oiled (rather than greased) bearing has brought about a sense of stability, ease and natural musical flow. It was the 'sense of stability' bit that troubled me before.

This is now a no-brainer for me. I just have to work out how to keep the oil in the bearing. In the meantime, an occasional drop of oil to keep things properly lubricated should prevent any damage.

Here is a picture of the KD-770D, now playing:

https://i155.photobucket.com/albums/s30 ... 1-1201.jpg

and here one of its Stillpoints OEM feet:

https://i155.photobucket.com/albums/s30 ... 1-1201.jpg

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