A repair and possible improvement in the Nakamichi CR series

The replacement motor I found for the worn original motor in the Nakamichi CR deck makes it perform more smooth and quiet. A remarkable improvement? Not really, because the smoother operation refers to the engagement of the transport functions and not to the reproduction of recorded tapes.

A ‘modern’ series cassette deck by Nakamichi

Nakamichi has rightfully earned the reputation to produce the best cassette decks of all … till the nineties! After that time the famous Japanese masterpieces were replaced by less inspiring standard decks, of which the basic versions were produced outside Japan in “less costly” Asian regions. De CR series is an example of the change in policy in the nineties. A series with it’s own sort of need for common repairs. That much has not changed.

My first exposure to the CR line was embodied in the low end CR1. The previous owner reported this CR1 was not working and he was willing to part from it for a very shy amount. When collected the sample proved incomplete, visually mistreated and very dirty, as usual. Hooking it up to mains a few lights appeared, but that was all that would happen.

At first investigation I noted the newish transport (Sankyo, by the way) in which the cam wheel was shriveled up to a tiny cam – tower. This little tower is driven by a worm wheel in stead of the belt drive in the classic Nak mechanism. This is an improvement as no belt can be slipping, a common fault in the classic mechanism. Also, in this modern Sankyo drive the potentiometer signaling the cam’s position has been replaced by three micro switches that feed back the position of the cam. Another improvement, for the imprecise potentiometer required additional adjusting of the cam mechanism, a complexity no longer needed.

This simple and well engineered mechanism should therefore supply eternal trouble free operation. But still herein problems occur at an alarming regular rate. This cam was stuck and would not function at all. Helping freeing the cam did result in a sudden moving of the cam and it’s driving motor and the CR1 started to play tapes. Easy? Close the case and start listening.

Short term success

After a few weeks the CR1 was released from duty and occupied a place in the collection. When operating this CR1 after period of rest the problem reappeared. Again the cam motor could be forced to work again, but the same trouble played up with increased frequency. Opening and cleaning this motor did not prove any help at first, so I started to look for a replacement motor.

A lucky hit was found in a electronics store in Rotterdam, DIL elektronica. Normally, DIL doesn’t sell electro motors but as an exception a bunch of them were discounted. This particular motor was a little bigger in size and meant for 6 volt applications as opposed to the 10 volt load in the CR1. I still thought it was worth a try.

Because the motor gets only temporal bursts of load when changing functions I concluded the overrated voltage value might not burn the motor in foreseeable time. And a little adapting would accommodate the larger size, I hoped. To accomplish that I redrilled the holes for the small mounting bolts. And redressing the layers of mu metal created the space around the new motor that was needed.

To get the motor into place (and out of its mounting position in the first place) quite a few parts need to be taken out of the cassette mechanism. The carrier on which the motor is mounted is bolted to the back plane of the mechanism and to the front as well. In the front a tiny ball needs to be taken out and several fragile parts as well.

Incredible improvement

At 10 volts the new larger motor appeared to run more relaxed then the original, so the engagement of functions take place smooth and silky, a real improvement. In any case, the CR1 now functions reliable so the goal is achieved.

Other versions will benefit from the same trick

This type of cam motor is used in any other modern Sankyo transport and will be subjects of failure in those as well. an CR4 in my collection had the same symptoms as did an RX202. As far as I can tell this motor is used in the CR series, but I’m not sure of the CR5 and CR7, which have a different mechanism. Most of the BX series and MR series are build around the Sankyo type of transport and use the same motor. In the RX202 the same 2-head transport mechanism as the CR1 is used, but it is placed upside down. Exactly the same cam construction is used with this same type of motor, shown in the following pictures.

This RX202 has a new replacement motor and plays without problems since. The next contender was the CR4. This machine uses a different transport with three heads and double capstan construction. Especially the double capstan construction with two large flywheels require more space, so less space for the cam is available. The placement of the cam is different, but the same type of motor is still used. The frame to which the cam and motor are fitted is shaped as an mirror image with regard to the single capstan versions. The following picture shows an CR1 frame at the left side and the CR4 at the right.

An other consequence of the different space for the cam is a little less room for the motor itself. This proved problematic for the larger dimensions of the replacement motor. Accommodating the extra size required removing a little edge from the frame of the transport. The first photo shows the tight fit of the original motor (see red circle). The next photo shows the space without the cam construction with the spot that needs removal to accommodate the larger new motor. The third photo shows the fit of the new engine.

The end results fits like a glove and works perfectly. The photo’s show also the large flywheel of one of the capstans, very different from the CR1. This flywheel is part of the capstan motor itself, a remarkable construction. This direct drive of the capstan does away with the belt drive. The belt still present is the driving belt for the second flywheel. This is a high end construction showing the pedigree of this nice piece of engineering.

The cam motor in the CR4 runs on 5,6 volt, definitely lower then in the CR1. This results in an ever smoother changing of functions and is another sign of the higher order in ranking. (by coincidence?).

Without the pun, this CR4 is a very nice machine and can now perform another few years up to its expectations. The flywheel construction is one proof of the quality built into the CR4. The copper clad case and frame is also witnessing the high upbringing and the bias and level adjustment features offer the same high level of performance. The sound of this machine is very tight and precise, without a hint of wow. A top effort for cassette sound.