Nakamichi Gear - Metric or Inch?

Salar

Member
2006-02-08 8:40 pm
Germany
Hello to all,
this question might fit into the analog source forum as well, as Nakamichi
was famous for it´s tape decks. But the machines mentioned
are the OMS-5 and OMS-7 CD-Players, mark one and mark two, introduced first around 1984.
These players used a belt for driving the laser head.
I have never seen this design in other CD-Players.
The belt detoriates and even though there are
still replacements available,I want to replace the worn belt with gears.
I measured everything and this seems doable.
But for milling the gear -that also drives another gear that will not be replaced -
it is not clear whether Nakamichi used the metric system or inch.
It could be a module (or modulus) of 0.4 in metric, in inch it could be 60dp.
(I do not know whether it is written 60dp or dp60)
Both are very close as Dp60 is a module of 0.433.
So bevor starting the adventure of having gear milled, it should be good
to know whether inch or metric are be the base for the design.
Does anyone definately know which norm Nakamichi´s engineers used?
I assume they made no difference if it was tape decks or CD Players.
So maybe some expert on Nak tapedecks might know the answer…
All the best,
Salar
 

ubergeeknz

Member
2018-08-31 12:32 pm
It'll be metric. But it's belt drive for a reason. If the head moves position for some reason, the belt allows some slippage at the end stops. Gears will not. And the gears will have some "lash" which the belt does not. I am sure it will work but may not work as well. The engineers knew what they were doing and a belt will last more than 10 years. My 2c.
 

Salar

Member
2006-02-08 8:40 pm
Germany
Thanks a lot for the answers!
I forgot to mention that the drive might have been produced by C.E.C.
But I do not find the source right now to proof this.
The Kyocera-DA910 and Universum AD-2000 were "clones" of the 1rst Generation Nakamichi OMS-5 / OMS7.
Interfacing was from Nakamichi, the laser was probably from Olympus
(Looks very similar to the Toshiba OPH-32) electronics were from Philips.
In the next generation, Nakamichi still used their interfacing (Remotes are compatible)
and the same belt driven, diecast base for the transport.
But the big laser was changed to a Sony KSS-123A, electronics were from Sony,
D/A section was Burr-Brown based


Some links, first the Universum, a defunct "cheap" brand from Germany,
with some Images of the belt driven transport:

Universum AD-2000 - vintage-audio-laser.com
The very beautiful Kyocera:
Kyocera DA-910 - vintage-audio-laser.com
The elegant Nakamichi:
Nakamichi OMS-7 - vintage-audio-laser.com

Now, look at the Universum clone:
On photo #10 (of15) one can clearly see the belt and the gear on the lower right.
As you can see, the belt is around a disc and on the shaft of the disc there is a small gear. Disc and gear are one part.
I removed it and did show it to a manufacturer of gears. He tried to measure the gear with a tool that looks more or less like a big screw.
The trick is simply to just let the gear run over the tool and feel with your fingers if it runs smooth. The tools used were for metric and Inch.
But the disc is too big to use both measuring tools properly as it blocks the tool.
This is why he could not say if it was DP60 or module 0.4. They are just too close. But it should be exact to avoid long time wear...

About the belt: Ratio is high, so any play of gear should be smoothed out...
 
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