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How to get your beloved CD-player from the eighties into the Digital Domain
How to get your beloved CD-player from the eighties into the Digital Domain
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Old 24th December 2017, 08:05 PM   #11
Salar is offline Salar  Germany
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Well, I did my mod 12 years ago... CD was at its heights
BTW, my Nak runs fine - but I overgreased some years ago. When there is time, i will have to clean the mech`s gears because the grease shortens the life of the belt.
There is one alignment I was never able to do, I do not remember the details,
but some frequency has to be injected into one IC to align the servo gain.

I did serve a second OMS-5II in November 2017
which I bought as non functioning from ebay. I found out that the belt was somehow transformed to tar, replaced it, cleaned everything and it ran fine.
I did start further alignment and was very happy to find out that everything was still up to the sweet spot. Gave it to my best friend who is very happy to own a Nak.

@Chris I still have an OMS- Mark One on the shelf with the big laser (Probably Toshiba or NEC, I do not recall the naming) If there is a need for one, I am happy to help out
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Old 25th December 2017, 04:32 AM   #12
anatech is offline anatech  Canada
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How to get your beloved CD-player from the eighties into the Digital Domain
Hi Salar,
OMS-5 or OMS-7? It is an NEC head. It's pretty large. If you remove the grey cover on a dead one you can see how the optics are laid out. The head is very much like an optics lab and you can see why these heads were so darned expensive when new. These very much are the best heads ever put into a CD player. Interestingly, it is a single beam system on a linear tracking mechanism. The alignment procedure is exacting and if followed, you end up with a system that will track just about anything. Of course, there is also the servo board modification that is very extensive. I'm really glad I set mine up.

What's wrong with the one on the shelf??

-Chris
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Old 25th December 2017, 06:25 PM   #13
Salar is offline Salar  Germany
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Somebody played witth the belt and but some extra gear on the belt motor. Also the guides for the tray are missing. Cosmetically in a bad condition.
Is the NEC head the same as Toshiba´s OPH-32? (Built into a Toshiba XR-Z70, that was rebranded by Kenwood or Alpine) They look very similiar and are both single beam.
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Old 25th December 2017, 07:59 PM   #14
Salar is offline Salar  Germany
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I forgot to mention: OMS5 and OMS 7 are identical. Same with the II-models. The only difference were a different VFD and IR Receiver, different keyboards, extra headphone board.
VFD, receiver and keyboards are passive components, driven by the same IC on the main board.
This difference made 1000$ in price.
It did cost only 600$ when ordering the parts as spare parts - front panel and remote included!
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Old 26th December 2017, 12:22 AM   #15
anatech is offline anatech  Canada
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How to get your beloved CD-player from the eighties into the Digital Domain
Hi Salar,
I would be surprised if they were the same, but never having seen the Toshiba head, I can't say.

You are correct about the differences between the OMS-5 and OMS-7 models. The price difference between list prices and parts is kind of reversed, wouldn't you say? Normally the parts would be many times the difference between the list prices.

-Chris
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Old 27th December 2017, 12:56 AM   #16
Salar is offline Salar  Germany
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I worked in a supermarket for about six weeks to afford my Nak OMS-5
and made a $1000 loan. This was in 1990. Got a service manual the same year
and I was a bit shocked to find out it covered both models
and the main boards are the same. A defective OMS-7 I bought later(just a voltage regulator was blown) gave the proof...

Last edited by Salar; 27th December 2017 at 12:58 AM.
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Old 27th December 2017, 03:56 AM   #17
anatech is offline anatech  Canada
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How to get your beloved CD-player from the eighties into the Digital Domain
Hi Salar,
That was never concealed from us. It was a very good thing that they were essentially the same machine. The person who bought the OMS-5 didn't lose anything except the remote control functions. The OMS-3 and OMS-4 used the same chassis and transport. The D/A section was different. At least the person who bought the OMS-3 got a good transport. The OMS-2 and OMS-1 were completely different animals. The OMS-2 had the TDA-1541A dual D/A converter. The transports were not nearly as good as the one in the OMS-3/4. I also have an OMS-4 to go along with the OMS-7. I got that later after the OMS-7. I didn't buy it new. I got it from a customer that didn't want to pay for a new head, I think I gave him 3 or 4 hundred dollars for it, maybe more. Then, I did the servo board mod, put a new head in it and set it all up. It has been a fantastic machine.

Having one manual cover more than one model isn't that uncommon. But I have to say that at least Nakamichi didn't try to hide anything. Did you also put the wired remote connector in the rear panel (and also a new rear panel?)? Teac was one company that would have a base model, then one of two models built on that base. These used the same service manual. Denon was another, Yamaha had separate manuals for each of their products.

-Chris
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Old 27th December 2017, 12:23 PM   #18
Salar is offline Salar  Germany
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I know, I know. I am just mentionimg all this in relation to a 1000$ difference in price. Stereophile published the review of a 1985 Kyocera DA-910 online.
It was compared to a Nak OMS-5, the sound of the Nak was described
as being inferior. Very funny, because to my knowledge,
both players are the same...
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Old 27th December 2017, 03:36 PM   #19
anatech is offline anatech  Canada
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How to get your beloved CD-player from the eighties into the Digital Domain
Well, no. The OMS-5/7 used the TDA1540 DAC which was 14 bit. The OMS-5/7 still sounded great and used the entire Philips chip set. I would very much like to convert it into a PCM-1702 DAC using the DF-1700 digital filter. That should sound pretty amazing.

-Chris
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Old 28th December 2017, 12:03 AM   #20
Salar is offline Salar  Germany
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As far as I remember the TDA1540 related chipset used something prior to i2s.
I think a DF1704 cannot be connected.
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