Nakamichi OMS-5

[anatech]

Hi gaborbela,
Okay. The tray has a bunch of nylon rollers held in by a clear plastic strip with rectangular holes. The tray assembly is an incredible pain to take apart. I do not recommend you touch this assembly at all.

I know because one "child" got upset with his OMS-5 and kicked it with the tray open (under warranty). The damage caused with the parts prices and labour priced it into the "not worth repair" area. Now this was clearly customer abuse, but Eric Moos (Nak area rep) decided to cover the unit under warranty !!!!! He did make some idiot decisions, that was just one. So I had to do this for warranty rates. After taking it apart I was able to convince Nak to send me a new transport complete. It is a big job. Don't go there.

You can lubricate the slide and gear section. Remove the drive gear, clean all the existing grease (and hair + ??) out. Relubricate with white grease only, apply sparingly. Extra grease always causes problems. The lube in the rollers is also white grease. If you just apply more you will make a mess. I warned you.

-Chris

[Heiney9]

Hi Chris,

You and I have corresponded before about Nak and Adcom equip. To add to this thread I have a question about a transport issue with a Nak OMS 3. Since you used to repair them perhaps you could give some insight. I've long given up hope that it can be repaired properly and w/o breaking the bank.

I've had this unit since new and it's been out of service for approx 3 years now. I used to be a salesman at the local high-end dealer that handeled Nak back in the day (mid 80's, early 90's). They are gone now and so is my friend the tech who used to work in the repair dept.

On to the issue. I can open the drawer place a disc in there close the drawer and hear a motor buzzing the standby light on the display will flash and within about 3-5 seconds the drawer open back up. I can do the same sequence even w/o the disc with the same results. Occasionally the disc will spin up and I can hear it speeding up and slowing down and the assocaited sound of the laser trying to track the info, but eventually it just opens the tray.

Any idea at all based on your experience if this is simply an adjustment issue or if the laser assembly is shot. This was repaired about 8 years ago and from my memory it had a new laser assembly fitted. I mainly would like to get it up and running for nostalgia, but I'd like to compare it to todays players. I always enjoyed the sound from this unit even though it only used a single dac instead of the duals of the 5 and 7. I've taken it apart just to look at it and it's built like a tank, very unlike today's units.

Sorry I just have the ability to repair anything of this complexity. I have done nothing with it other than open her and look.

Regards

Brock

[anatech]

Hi Brock,
The drawer thing sounds like a poor contact with the drawer position switches. You should measure the little switches on the transport. Might be an easy fix. (OMS-4 had dual DAC's).

The laser head will not need adjusting. It may need a new disc motor. Do not allow anyone to just adjust the unit. Some laser heads had a problem where the lens assy would stick on the post. Head replacement was the only way to fix that. Your unit may not work with the top cover off (normal). Those were NEC transports. Harmon Kardon used the same one with fewer options.

I wish we lived closer to each other.

-Chris

[kensell21]

Hi All,
Ive just joined this forum site and would like to ask others for more info about the Nak cd4 as I've done a search and found this thread.
After a long time with vinyl using a michell gyro SE/techno arm A/ Ortofon MC 30 Supreme.
I wanted to compare it with my slightly dusty 12 year old Nak CD4 player with identical music.
A MoFI vinyl and MoFI cd of Cat Stevens Izitso.
Well no brainer really and I wasn't expecting it to be.
But it did get me thinking that I must get round to replacing it for the music that I can't get on vinyl.
Could some tell me what the transport and DAC arrangement is in this machine? I will also need the clock frequency.
I like the look and feel of this machine so I am thinking about putting a new clock in it from Trichord Research.
Also would the transport of this machine be good enough to use as a dedicated transport?
Its probably had minimal use over the years. If all else fails I'm thinking about going retro and find a decent Teac Vrds transport or even a Pioneer stable platter, but that topic I might leave for another thread.
Thanks

[waves]

Hi Chris,
Wow! I'm really impressed with the helpfulness of this thread and its participants, and I've learned alot. Especially to not give up! I stopped looking for Nakamich information a couple of years ago.
I had played my OMS-2A daily until then. It started having trouble reading discs, but the lens looked clean. Besides, when discs did play, there was more skipping that eventually became a continuous clicking. If I remember correctly, the sound was at a higher pitch than skipping caused by scratches. At any rate, I decided to observe the motor's spindle as it ran, and it seemed to have a wobble. I compared this with several other cd players, and mine seemed like it was spinning on worn bearings.
I'm assuming the motor needs to be replaced. I've read in previous posts about things I wouldn't touch, but I'm wondering if I could replace the motor. Since I couldn't find any Nakamichi motors in the parts section, I was also wondering where else to look for parts.
Thanks,
Dave

[Salar]

Hello Dave,
maybe the motor of your OMS-2A is from Mabuchi:

http://www.mabuchi-motor.co.jp

Another supplier might be Copal

www.nidec-copal.co.jp

Mabuchi built the disc-motor of my OMS-5EII, the Copal was for the laser unit of the OMS-5EII.

They probably are discontinued, but maybe Mabuchi or Copal have contemporary models with the same specs like the old ones?
One problem will also be mounting the disc table of the OMS-2 on the new motor, because it has to be fixed in a certain height.
Maybe, making something like a "print" will help.
I do not know the english terms, i think at some kind of artifical clay which does not glue and can be modeled. This can be stuck between disc table and the motor body before disassembling them. When it has dried, it can be used as a reference for fitting the old table on the new motor.
Hope this helped a bit,
Salar

[anatech]

Hi Dave,
Check the nylon thrust bearing at the top for wear. It will have a dent.

You must sand this out, then fine sand 'til it's smooth. I use damping fluid to lubricate the ball bearing after that.

The motor is replaced by a standard Mabuchi CD motor. Cut the shaft to the exact same length and round the end. Measure the table height carefully first and make sure it ends up at the same height. Use nail polish or thread lock on the shaft before sliding the table on.

The exact Nakamichi motor came with a brass spacer. (NLA) I think new mounting holes need to be drilled also. It can be done, I did many a long time ago. My brother has the same player - still. It works fine.

-Chris

[Salar]

BTW, I had an OMS-5/7 for some weeks bevore buying a OMS-5II/7EII.
As far as I remember, the sound of the OMS-5II/7II was crisper with deeper bass compared to OMS5/7

[anatech]

Hi Salar,
The OMS-5/7 has a superiour transport, 14 bit DAC (TDA1540) and a great filter. The DAC in the type II is far superiour to the first ones. If only they kept the original transport!!!

-Chris

[Salar]

Hi Chis, Hi Dave,
hope Niro Nakamichi will read this some day...