">
Sankyo control motor cleaning procedure (by Andy)
The problem
On Nakamichi decks that have a Sankyo-made tape transport, it is common to see a problem develop where the deck's tape transport starts to act very strangely, and the deck may even stop responding to commands.

If it can be determined that the deck does have a good idler tyre, then the problem is quite often in the control motor mechanism. These photos will show a couple of techniques to address this problem.

DISCLAIMER

This is meant as a GUIDE ONLY. I am simply a Nakamichi enthusiast. I am NOT a factory authorized Nakamichi technician. I am NOT LIABLE OR RESPONSIBLE for any damages that may occur to you, your property, loved ones, pets, cassette tapes, stamp collection, the lunch you had last Thursday, or anything else you may own if you perform these repairs/procedures. If you choose to perform these repairs/procedures, YOU DO SO AT YOUR OWN RISK.

The symptoms

  1. Tape function buttons no longer responsive
  2. Several tape function buttons lit up at one time
  3. Erratic behaviour
  4. Tape jamming, tape eating

The diagnosis

  1. Dirty electrical contacts inside control motor
  2. Dirty control motor leaf switches

It doesn't know what to do!

This photo shows typical "confused" behaviour, indicating a problem with the control motor mechanism. This CR-7 is literally trying to do everything at once.

Sankyo transport, seen from above

The two areas of interest are indicated by the arrows.

Disconnecting the transport

To service the control motor and leaf switches, the entire tape transport assembly must be removed. The first step is to unplug all connectors leading to the tape transport. In the case of this CR-7, these two connectors must be unplugged, and then...

Another disconnection

In the case of the CR-7, this connector, which leads to the deck's playback azimuth motor circuit, must also be unplugged. (NOTE: The two connectors that were shown in Fig. 3 are located just beyond the top border of this photo.)

Removing the transport

After cutting any other wire ties that might restrict movement, it is now time to remove the actual tape transport. Start by removing this screw on the top...

Removing the transport (cont'd)

...And then remove these two screws on the bottom of the transport. Try not to disturb the delicate wires here!

The transport is removed

After removing any remaining front pieces that may block the way, the transport is pulled straight out of the front.

Be careful, be gentle

SLOWLY remove transport whilst grasping top of frame.

Removing the control motor assembly

(This view shows the rear of the transport assembly.) On the CR-7, removing exactly five screws frees the entire control motor assembly. Here are the first three screws. Screw #3 is accessed through a hole in the circuit board that is mounted on the back of the transport assembly.

Accessing the inner cassette cavity

I guess I lied when I said that you must remove five screws to free the control motor. One of the screws is hidden behind this wall, so you must remove the two small screws indicated in this photo and remove this black metal cassette well cover in order to access that screw. So it's a total of SEVEN screws. BE SURE NOT TO LOSE THESE TINY SCREWS!

After this, just one more to go...

Once the cover for the inner cassette cavity has been removed, the small screw that retains the white control motor cam gears can be accessed and removed.

The final screw

Unfortunately, I don't have a good photo showing the location of this particular screw, but hopefully this illustration will be clear enough. (This photo shows the transport still installed in the deck.) The screw, whose position is indicated by the dotted yellow drawing, is a long brassy metal screw that holds the leaf switches onto the control motor assembly. This screw is visible at the front of the transport on the right side.

The control motor is freed

Once the screw that attaches the leaf switches to the control motor assembly is removed, the control motor can easily be lifted out of the transport.

Cleaning the leaf switches

GENTLY squeeze the leaf switches together whilst scrubbing in between with stiff paper soaked in DeOxit.

Nice and clean

Since the leaf switches are also quite exposed at this stage, it is very easy to clean them. These switches have now had a THOROUGH scrubbing and are ready for duty again.

Time for some exercise

Sometimes the control motor's internal contacts can be improved by running the motor thoroughly. For powering the motor, a variable DC power supply is recommended, but if one of those is not available, a 9-volt battery can be substituted. Be sure to flip the polarity and run the motor in both directions. Run the motor for at least 20 to 30 minutes.

A crucial step

This is one of the most important steps in the entire process. Before, during, and after the control motor is exercised, spray DeOxit contact cleaner into these four small slots on the back of the motor. These slots lead directly to the motor's internal electrical contacts.

Almost done

Allow the DeOxit contact cleaner to soak down into the control motor. Give it plenty of time to thoroughly penetrate down onto the motor's internal contacts. To ensure that the DeOxit is coaxed down into the motor, try to position the motor so that the motor shaft points downward and the terminals on the back of the motor face upward. Once this is done, the control motor and leaf switch assemblies can be put pack together and re-installed into the deck. Make CERTAIN that ALL pieces are EXACTLY in their original places. One piece that is especially important is the small metal lever shown in the next step.

A very important detail

When the re-assembled control motor and leaf switches are re-installed into the deck, watch out for the small metal lever that is highlighted in the photo. Note that there are THREE black leaf switches but FOUR cam wheels. The fourth cam wheel should engage with this small metal lever. WHEN THE CONTROL MOTOR AND LEAF SWITCHES ARE SLID BACK INTO PLACE, DO NOT ALLOW THE METAL LEVER TO SLIDE DOWN BEHIND THE WHITE PLASTIC CAMS. MAKE SURE THE METAL LEVER RESTS ON THE FOURTH CAM.

Control is restored

Once the deck has been re-assembled, verify that all of the tape functions (PLAY, FF, RW, PAUSE) work consistently. Then load the deck with an old cassette and test all of the tape functions again.

A few final notes

  1. These repairs/procedures are based on the assumption that the control motor is not worn out. On decks that have had significant use, it is sometimes necessary to rebuild the control motor or even replace the motor entirely.
  2. The wires soldered to the control motor terminals do not need to be disconnected unless the motor is being rebuilt or replaced.
  3. If you choose to work on your own cassette deck, it is HIGHLY recommended that you obtain a copy of the deck's original service manual.

Copyright 2007 Naks.com