Monday, January 19, 2009

Rolling On..

While still looking for a solution to test the repaired board seperately, I move on with the other aspects of the Nakamichi. Today, I removed the transport. This involved removing some cable ties, and freeing four mounting screws that hold the transport to the main frame.

The transport used by Nakamichi in this period is truly a engineering marvel. It was a versatile transport that had been used as a basis to produce fully direct drive, semi-direct drive, belt drive, auto-reverse and a few other configurations.

It is a simple, but effective and very stable transport that has few problems. The tranport features two capstand that rotate at different speeds. This allows mechanical noise to be distributed and reduce flutter and modulation. The aluminum chassis of the transport is damped by plastic resins that absorbs vibration and inert. The transport does not use solenoids that give a 'thumping' noise on other decks. These wear out over time and induce mechanical shock. Nakamichi uses instead a near silent cam mechanism that operates the various modes.

Once the cable ties and screws are removed the transport is carefully removed from the main chassis. The transport is then inspected to asses its condition. From far, it looks not too bad, but a closer look reveals some issues. Some parts of the transport is covered with a layer of grime and dust.

The motor spindle which drives the idler is corroded! Some cleaning with solvent does not seem to help, so this needs to be fixed.

The classic transport uses a swinging idler wheel to drive the spindles. This is a very simple and reliable method. The idler wheel has a rubber 'tire' that needs to be changed althoug this is not often.

In this deck, the tire looks worn and cracked. It definitely needs to be changed.

The back of the drive consist of a back plate that mounts the capstan motor, thrust bearings for the capstan flywheels and the cam mechanism for overall transport control. Removing this, brings access to the capstan flywheels and cam mechanism.
The lubrication between the thrust bearing and flywheel is hard and almost dry. Small wonder for a deck of this age!

When turned by hand, the flywheel does not seem to be very smooth and some resistance is noted. The flywheels have to be removed.

The capstan drive belt, noted at the back on the left picture is quite slack and also needs to be changed.

Bad luck - the edges of the capstan are corroded! This edge comes into contact with the belt and they are rusted!

The other flywheel, visible slightly in this picture, also has the corrosion on the surface that contacts with the belt.

This is a majr problem and needs to be solved if this deck is every going to sing again!

A solution is required to remove the corrosion from the flywheel so that the surface does not damage the capstan driving belt.

1 comment:

  1. Be very carefull removing the rust. If you vary the radius, you may end up with bad W&F problems and different angular speeds, so tape may loos contact with the head, and / or the machine could end up eating tapes.