Nakamichi Restorations

NakTech · Sep 8, 2015

jayants · Sep 8, 2015

Great stuff!!

My NAKs will be on its way 2 ur DEN very soon Umesh Ji

jaisinghdelhi · Sep 8, 2015

Thanks Umesh, For restoring my deck. It was a wonderful experience interacting with you. I must say that your knowledge,eye for the detail and the perfectionist nature is the key to your success.

The humble cassette has given the L.Ps and C.Ds a run for their money. Apart from my CR3, Dr2, ZX7, very soon I will need your help in setting up my CR7 which is in transit.

Will post the Video of my ZX7 recording and playing.

Thanks Again,
-Jai

frend2001 · Sep 8, 2015

Remarkable Job Umesh.

It sure is very detailed and comprehensive restoration.

thumbs up

deba · Sep 8, 2015

those golden days of analog audio........

Hassan Khani · Sep 8, 2015

Please do post video of the deck after restoration. Good to see it in action after the hardwork. I felt the pink LED door lamp a bit odd but may be the choice of the owner.

It feels good to have someone so knowledgeable about NAK decks and hence more confident in acquiring such higher end NAKs and restoring.

George T · Sep 8, 2015

Just for the Glory of the Old days: the Nakamichi TX 1000: US $ 7000/- when it came out in the market in the 1980s

Salute to those heady times!!!

NakTech · Sep 8, 2015

Adding some Videos. I don't have much after service as it was taken away quite fast.

Here they are. Don't expect much video quality..

Slight hum and electrical interference that may be noticed is because the earth wire to chassis was not connected for convenience. The completed deck is noise free.

ZX7-06898 Playback

https://www.youtube.com/watch?v=p8D14f-bAMc

ZX7-06898 Recording on test bench - Sony Metal XR tape

https://www.youtube.com/watch?v=gKvsN-31b1E

ZX7-06898 Recording - TDK D Tape

https://youtu.be/vXjhW5GjCds

This last video is from the owner..

https://video.fmaa1-2.fna.fbcdn.net...=6e78b82f8a7a6af6b3f0d0cde53e86d6&oe=55EEE663

navinsinha · Sep 8, 2015

Hi Bro,
This is simply superb work. Not many people in India would be able to do such work! Kudos to you!

nakamichi · Sep 8, 2015

Outstanding work umesh sir....truly amazing

frend2001 · Sep 8, 2015

The nak bug bites.....

NakTech · Sep 9, 2015

deba said:
those golden days of analog audio........

those golden days of analog audio........is certainly back...and rocking...

Technics_Fan · Sep 13, 2015

Great restoration and photo story...

I have question though .. the wow and flutter measurements in audio tester that you have posted.. is that the WTD RMS?

Techs usually tend to do multiple runs (15 to 20) to arrive at a weighted average of the wow and flutter WTD RMS measured with a reference tape containing 3150 hz tone ..
The reason I ask is that the .067% WOW and Flutter is slightly more than the published specs of 0.04% for a classic transport..Is this because of only one run..

Technics_Fan · Sep 13, 2015

Sorry for the multiple posts...I also wanted to ask you how will you factor out the residual wow and flutter from the reference tape..I know it is going to be minimal in a good reference tape there will be still some wow and flutter that needs to be factored out to arrive at the actual Wow and flutter specs...

Is it generally not a good idea to use reference tape for only speed calibration and signal generator for wow and flutter measurements once the deck is calibrated to the right speed...Is that how you do it...I know evaluating a accurate W&F specs is probably hardest thing to and wanted to contemplate your expert views...

NakTech · Sep 14, 2015

This is a gray area for me too. I have asked this same question (your first post) to Mr. Muller, the developer of the Audio tester software and the reply was "It is the value auf the selected standards (e.g. NAB JIS DIN/IEC/CCIR)". He also said he compared and confirmed the readings with a Rohde & Schwarz UPL. I did not gain much knowledge from this explanation other than the fact that the tester is accurate. Then I thought of hunting for a R&S UPL and found that units that are old and has no guarantee of being accurate cost above 3000 USD. :sad:

What I find by experimenting is that the Audio tester reads continuous peaks at a rate set by the FFT averaging. If the buffer is more it reads low values, if less higher. This is something we can manually select. I have no clue how many seconds averaging has to be done to get an accurate representation of the weighted RMS. The only way to find this out is to have an analogue wow and flutter meter which is calibrated and certified recently.

So I don't use long buffers to show a low average value. I read it with 1 sec average and take the maximum value in 10 sec. I run the tape for 30sec noting the peaks value within a 10 sec window. So I get 3 values. Instead of averaging I take the Max value so that I am sure the average would be much lower. Once this number is known, I capture the graph with the set reading. This always is consistent with the weighted peak readings published by Nak. The published weighted peak is 0.08 for ZX7. The reading in the graph is 0.07 aprox..I always give a service report along with the deck and I mention the details such as if it is peak or rms. I don't believe in taking 20 to 30 readings and averaging. Once the head engage, the meter jumps to a high value and within 2 sec, it comes to a more or less steady reading. The numbers keep varying, but not more than plus or minus 0.01 variation would be there.

About the published wow and flutter of Naks: The wow and flutter for all standard transports is not the same. Actually there is no such official model of transport called the Standard transport. People just call it so because these are not the OEM transport by Sankyo.
Right from 480 (w&f =0.11 peak/0.06rms), 580 (w&f =0.1 peak/0.05rms), 680 (w&f =0.08 peak/0.04)rms to ZX9-DD (w&f =0.045 peak/0.022rms) all are standard transports but there are significant improvements in performance in these transports. All manufacturers specify the max value of peak and rms w&f. Nakamichi peak of 0.08 means 0.08 max or lesser. So as long as we don't see any value above 0.08 any time in the reading, it is surely within speks. For a belt drive, I feel any value of 0.1 or below peak is good.

I have not given any wtd rms readings in my reports or the posts here so far because I don't have an authentic reference for it. My T-100 can read it, but that is again restored by me and it require a standard wow and flutter generator to calibrate it. (Which I don't have). I am testing some other tools too for rms measurements, but I won't use it to publish speks until I am convinced that it compares to a real meter.

About the test tapes: This is another gray area. I use a Sony WS-48B (it is 3KHz) tape to set the speed as well as to measure the wow and flutter. This is the most widely used tape now. There are many other brand tapes too including nakamichi. They all vary a little in speed and residual w&f but within 0.3% or so as tested by some techs who have all the tapes and devices to measure them.

The residual wow and flutter of the test tape itself is generally omitted. In theory, it should be accounted for, but the reason why it is omitted is because, the test tapes are actually produced on modified open reel machines like studer A80 or Otari. They run at 7.5 ips. At that speed, it has a W&F of 0.06 peak. 12KHz is recorded at that speed. When played back at 1-7/8 ips the frequency becomes 3KHz (this is the NAB and JIS standard used by Nakamichi, 3150Hz is DIN standard) and the W&F peak also reduce to 0.015 peak. This is in theory but the cassette shell will induce some more onto this. To minimize the effect of the shell sony use the ceramic composite tape guides and precision rollers and slip foils (confirming with BASF reference cassette mechanism). But I know that the Nakamichi test tape has hand written speed variation and residual w&f value on each tape. So there must be a way to account them on the readings, but I don't know it yet. Moreover, all the service manuals mention only to load the test tape and take reading (even in the manual of T-100). They don't say anything about the residual w&f on test tape. So I think that level of accuracy is not intended. After all, we are only dealing with 1/8" 1-7/8 ips cassette meant for consumer market. It is only a shadow of a professional ATR which runs at 15 and 30 ips.

Bottom line: There is no mathematical way to derive w&f rms from peak readings because the variation pattern is random and complex. It is easier to read peaks and get them within speks. I will end up buying a w&f meter eventually to read rms values ..

analoguemusic · Sep 19, 2015

Hi,
Here is the youtube link for the Deck in action. It's doing what it is supposed to; perfectly.

https://www.youtube.com/watch?v=bN7eA21DO_I

Thanks,

jaisinghdelhi · Sep 19, 2015

Hi,
Here is the you tube link for the ZX 7 in action. Its performing exactly as it should.

https://www.youtube.com/watch?v=bN7eA21DO_I

Thanks,
-Jai

frend2001 · Sep 20, 2015

wow....amazing

Analog rules...

musiclover07 · Jun 6, 2018

Dear NakTech

I need your help restoring my Nakamichi 480 pls help i have sent u my contact details

thanks

audiophile29 · Aug 12, 2021

NakTech said:
Dear All, thought of posting some details of the Nak restoration work on this thread. I am planning to update most of the work I do under this thread as long as the owners of the decks have no objection in doing so.

Any comments, advises and discussions are welcome. But I request all of you to kindly keep the subject matter limited to the repair and restoration of Nakamichi Tape decks only.

ZX7 - Serial No: 06898

This ZX7 was in storage for a long time as per the information available. As it got couriered to the owner, the left side posts on the transport broke (this is a common problem when the unit is not packed properly and sent via courier). The transport was not ejecting the door, it was pushed inside and jammed.

https://goo.gl/photos/XuE5a9GyS23ERAWQ6
https://goo.gl/photos/ygRbnh1ErzjEpD7a6

The worst part was that the azimuth ribbon got trapped between the door assy and the chassis and got a deformed.

https://goo.gl/photos/sLLDFQAZTakA2cvc8
https://goo.gl/photos/LJ7DvBrtXyiRdgu48
https://goo.gl/photos/pfLFMRusPHxQSUpK9

As this is the most vital part, this was taken up first. Here is some pictures of the fix.

https://goo.gl/photos/rs42XChbp5HFfS8x5
https://goo.gl/photos/seKEeEkmSSSDx9698
https://goo.gl/photos/uZwH65nntmbmTKT86
https://goo.gl/photos/9f3GJDGQHSTUtWWh9
https://goo.gl/photos/qRWPRQtA2L91MDRcA
https://goo.gl/photos/6KnUQzV5JJrWRECCA
https://goo.gl/photos/XfBVdb4uw8zgp7oR8

After making sure that the ribbon slide smoothly, moving ahead to dismantle, clean and relube the dirty transport.

https://goo.gl/photos/RGmUazZP8XWjGRbe9
https://goo.gl/photos/RnNgvBLXkjCLPs2Z8
https://goo.gl/photos/qzqSk8MtULJaTy8M9
https://goo.gl/photos/RG9yfYeCrQimKRDp7
https://goo.gl/photos/pT7berKfXMut9rPz6
https://goo.gl/photos/wbw6KpoWG98X4Fmj6

Cleaning the sub mechanism assy, motor pulley and install new idler tire.

https://goo.gl/photos/b5bmLovZy9RWkxtz7
https://goo.gl/photos/fUMbuJakRQc6B1VR8
https://goo.gl/photos/eP4abSf3cJJ3wJK6A
https://goo.gl/photos/mEzqyinBUgof8jCeA

Cleaning the main mechanism assy and other parts and lubrication.

https://goo.gl/photos/JA2kDTVS6s1pkW2K6
https://goo.gl/photos/MkunDUYKx4Mo3ySB7
https://goo.gl/photos/WEveKP5ZTRH4KtRPA
https://goo.gl/photos/sNFLUSCi4X3Rcfq89
https://goo.gl/photos/Trvy2sprJa78W8HZ6
https://goo.gl/photos/Xum97hQF5hbZXhFh8
https://goo.gl/photos/gA7PtMuGm3biLSuP6
https://goo.gl/photos/L3tnfQe96h8f5fJ8A
https://goo.gl/photos/ubyXi6zP95VgG5hP9
https://goo.gl/photos/7YCf1NgRF9Ar6TbW9

Getting some parts back together.

https://goo.gl/photos/2yQC1pCMCXT6KqGW7

Removed head block assy.

https://goo.gl/photos/kZ7pdcJz1qqXcaeJ9

Most of the other parts are back together.

https://goo.gl/photos/4qfre58wsKYfdg797
https://goo.gl/photos/godU6P9x5NFi7dPT7
https://goo.gl/photos/mNs8HmSE4ei5Tomk9

Missing felt on the back tension arm.

https://goo.gl/photos/gML3GMiRgmHrQ9RX7

After fixing new felt.

https://goo.gl/photos/EAmdJHz2LUJPUmPm8
https://goo.gl/photos/h4rz55srZZfD9P4G6

Removed pinch roller assy

https://goo.gl/photos/hGUWWYVEnDXYv1B47

After cleaning

https://goo.gl/photos/iHrvvEjq62ezPs6K6
https://goo.gl/photos/T4iqBhz9oUkNpm7E7

New capstan belt (nakamichi's original dimensions Vs the local belt that was installed)

https://goo.gl/photos/LaFVha35pcYho4N6A
https://goo.gl/photos/o6eYLSJB9G4huxCBA

Guide height alignment.

https://goo.gl/photos/APMDJ7NF21WEERDBA
https://goo.gl/photos/93tvAFtoHCsffx7k6

The unit had missing head alignment screw on the record head. The deck was used like this for long time and the record head was worn wrongly. So replaced the record head.

https://goo.gl/photos/VNfsiT3L7qJ9pBCe7

Transport is back together

https://goo.gl/photos/d8zJaJkXBvVp1HMy9
https://goo.gl/photos/dy9iUSEq63yeNNAL8
https://goo.gl/photos/tHBvXyqoC6nUUmvL7

I love clean transports...

https://goo.gl/photos/u7T5chZ4HLF2mQDh8

Cleaning the rest of the mess....

https://goo.gl/photos/FcPRsRUCdoUgcMNB7
https://goo.gl/photos/udAMeE2LnUZNvwoBA
https://goo.gl/photos/cr97knX8BT5xsjvF6
https://goo.gl/photos/9v3guEzj2wupPAoV7
https://goo.gl/photos/6UrVGCX4LqCH1BgZ6

All switches cleaned and lubricated with very special contact cleaner and protector. All trim pots lubricated with separate special lubricant for carbon and conductive plastics.

https://goo.gl/photos/yNdinVDtR9UmWNPr5
https://goo.gl/photos/Vvi4ZZA5Vp2ugFmH6
https://goo.gl/photos/FZe9omWmf5zJMPcS6
https://goo.gl/photos/rxazo81gAALvEKat5
https://goo.gl/photos/JsAYZBBDX7kSnUncA
https://goo.gl/photos/jWVCo6Fq74ZnbWGS9
https://goo.gl/photos/GUVoA3Z6Fyugjg5a6
https://goo.gl/photos/dzHi9E3q9oq1ry9Z6
https://goo.gl/photos/8GnWtKPFLo9wJaZc7
https://goo.gl/photos/g2EkW9CuaNPmEyf37
https://goo.gl/photos/FWnHvHwtDHPt5cCaA

A transistor was short and the fuse failed in the first power up.
Replaced the fused with new types.

https://goo.gl/photos/oXpFyyjDdPTda6KNA

The counter also had faulty components. It gave some hard times but finally tamed.

https://goo.gl/photos/5oDzriBH3LRUNRnM8
https://goo.gl/photos/o3fkFSK95x13SyxF8
https://goo.gl/photos/M353wHRMUhAsZkpT6

Replaced blown door lamp with LED. Also replaced the shut off lamp to LED as a preventive maintenance.

https://goo.gl/photos/N4RYvV9WrL5r9eFs7

Dirty Dolby board

https://goo.gl/photos/2uBQD2nbSSgyZ8FM7

Dirty inner side of face panel

https://goo.gl/photos/XjbdU8z4kQkvoRwD7

Power on tests

https://goo.gl/photos/aiW13PTEZ7Kg8pQ57

Cleaning the face and panel parts

https://goo.gl/photos/FeYaXA96C141X3yZA
https://goo.gl/photos/ymsWv2e36ge8JmKs6
https://goo.gl/photos/ftUWEi89ZGUKpsGa7
https://goo.gl/photos/qS8Jxn6vKzsVnZGg6
https://goo.gl/photos/KtKoqMhAku9nJMCEA
https://goo.gl/photos/Ajs5nSV4C65w7ku16

All PCBs cleaned and sprayed with anti corrosion spray.

https://goo.gl/photos/gZk9RNwv2Fr4yQSv7
https://goo.gl/photos/u7nqVz3WaJsf2QyA8
https://goo.gl/photos/NjvaPAAHiTNqYrZ87

Front face..
https://goo.gl/photos/usFcEFmHoFsswiZT7
https://goo.gl/photos/ukj8MtMR5WcdNCLh9

And all in one piece again..

https://goo.gl/photos/dCKVfHySCd4vLY2eA
https://goo.gl/photos/65sSf5McdeVmWZSFA
https://goo.gl/photos/F9Mx9BbMVDiYisoM9

After full calibration, the Test and measurements were done.
All met or exceeded the published specifications.

https://goo.gl/photos/HhAqkCHSepfqL9aZ8
https://goo.gl/photos/poTeNkrfnuAWB6W99
https://goo.gl/photos/k5VnxdpDQ6FmLKGD8
https://goo.gl/photos/sLGqK9KBUVNkq9xC9

This proved to be truly a remarkable deck. The sound quality on playback as well as recording was outstanding.

Finally the well pampered ZX7 went back to the owner....to make him proud. The promise of the Nakamichi is still kept.

https://goo.gl/photos/5UagBpNca3edZZyE7

Can you help ? I too have a ZX7 which needs some repairs /service
Regards

shishir

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