Nakamichi CR-3 and CR-4 Ground connection mod.

Both the CR-3 and the CR-4 from my experience do sound considerably inferior to other 3-head Nakamichi decks. Usually the Sony Dolby chips got the blame, however the same chips are working fine in many other decks. Just recently I've restored to full health the CR-3 from my collection and the sound of that deck was, well, again underwhelming, similar to what I've experienced before with the CR-4. This time, however, I've recognised that I've heard that kind of sound deficiency in other equipment and it is usually caused by an incorrect earth arrangement. I just couldn't believe that Nakamichi could do that kind of mistake (or was it a deliberate mistake?!). Both the CR-3 and CR-4 share the same power supply layout and the same connection of the electrical "ground" to the metal case - by a screw holding the power supply pcb to the case. On the majority of the other Nakamichi decks the "ground" is connected to the case near the input sockets (there are some exceptions like the 1000ZXL with it's massive distributed ground but that is just a completely different approach requiring a massive metal frame and good with multiple circuit boards). I've made a simple experiment - I've cut the ground plane connection pcb track between power supply ground and the screw pad and installed a couple of 2-pin jumper connectors - one in that track cut and the second - on the input/output sockets "jack pcb" across C373, connecting the case to the "ground" at the input connector. When I listened to the deck the sound difference between the original case connection and the modified one was immediate and the sound with the mod was much better. As the mod is so simple, so effective and easily reversible I thought I would explain it here. The picture shows exact points you need to do the changes to: 1) cut the track on the power supply pcb where shown and 2) join the C373 pins together with a bit of wire. That's all.

Usual warning - if you open the top cover do it with the mains disconnected and take care not to damage anything, including your valuable self!