Nakamichi BX-100/BX-125/BX-150 cam motor
An article from Pieter's Knowledge Base
As of the BX series of cassette decks, many
Nakamichi decks have been fitted with a mechanism
manufactured by Sankyo. It can be found in
the BX, CR, DR, 'Cassette Deck', ZX, and
MR series (but not all models of those series).
The cam motor is responsible bringing the
heads into position, as well as some other
A well known issue with these Sankyo mechanisms,
is that the so called CAM motor (aka control
motor) stops working after a while, especially
when the deck is not used for a longer period.
The so called carbon brushes inside the motor
get oxidized and no longer make proper contact
with the so-called commutator of the rotor
(the part of the motor that spins around).
The result is that the deck will no longer
go into play, pauze or record modes, or if
it does, will not return to stop mode. However,
the deck will often be able to wind the
tape forwards or backwards.
When this happens to your deck, the best
thing to do is to replace the motor with
a new one. Unfortunately, these motors are
no longer available, and it's difficult to
get a substiture that is easy to fit inside
your deck. The best next thing is to clean
the motor. Elsewhere on the internet you
can find instructions that basically boil
down to spraying some contact cleaner (e.g.
Deoxit) into the motor. This will work for
a little while, but at some stage, the problems
I have developed a procedure that will make
the cam motor last longer. It involves opening
the motor itself and cleaning it thoroughly.
Below I will show you how to do it. The instructions
are based on the BX-125E deck, and also apply
without significant changes to the BX-100
and BX-150 (as well as their European E-versions).
Other models in the BX series are probably
very similar as well. With other series probably
other steps need to be taken to remove the
mechanism form the cabinet (it actually might
not be required at all), or to take the mechanism
apart, and the cam motor might actually be
in a different spot. Please search the internet
for instructions applicable to your own deck,
or consult a service manual.
Update: the procedure I describe below does not always produce long lasting results. I therefore strongly recommend that a new motor is fitted. I personally use the RF310-TA11400 motor, but there has been some discussion on forums that this is not a good motor. I personally think it is good enough, but some repair professionals disagree with me. I can at this time not recommend another motor from my own experience. Please search the internet for a solution that meets your demands.
Warnings and disclaimers
- These instructions are meant for repair professionals
and experienced electronics hobbyists. If
you have never repaired electronic/audio
equipment before, than this procedure is
probably not for you.
- When you carry out the instructions below,
you do so at your own risk. I will not
held liable for any damages that occur
you try to repair your own deck.
- Be sure to disconnect your deck from mains
power, as there are parts inside that are
high voltage and could result in dangerous
- Take your time, don't rush or force anything.
If you do, something will likely get broken,
possibly even beyond repair.
- Read all of the instructions below carefully
before starting to work on your own deck.
You will need some tools in order to get
the job done:
- Q-tips for cleaning purposes
- Big Phillips screw driver (A) (to open cabinet)
- Medium size Phillips screw driver (B) (for
- Tiny Phillips screw driver (C) (for the tiny
heads of the screws that hold the cam motor
to its assembly).
- Tiny slot screw drivers 1mm (E) and 3mm (D)
or so (to open and close the motor respectively).
- Lubricant for low speed plastic gears. I
use Robbe 5532, which I bought at a model
kit store. You can also try to get your hand
on the Nakamichi recommended Molykote X5-6020
grease, which I found in cans of 1kg only,
so that's going to be expensive.
- Ball bearing grease (optional).
- 9 volt battery, or another 6 to 9 volt DC
source, so we can test and run the motor.
- Drill machine with a 1 mm drill bit (optional,
to drill holes into the back of the motor,
so it will be easier to spray some kind of
contact cleaner into the motor in the future,
- Some kind of contact cleaner (not in the
picture). I understand that in the Americas
people recommend Deoxit, but as this isn't
sold in Europe, I can't tell how well it
works. For my European readers, I recommend
either Contact Cleaner 390 (by Kontakt Chemie),
or even better, a combination of Kontakt
60, Kontakt WL and Kontakt 61 (please do
not use Kontakt 60 alone, as this is very
agressive stuff that will make matters worse
for your motor in the long run if you do
not remove it after use).
- A pair of tweezers (not in the picture) to
remove screws and other parts, and to put
them back (see note below on using magnetized
- Tie wraps (optional), to tie back all wiring
in the deck after the repair.
A note on using magnetized screwdrivers
Magnetized screwdrivers are handy, because
it makes it easier to remove screws. However,
I have been told that when a magmetized screwdriver
touches one of the heads or capstan, or even
comes close, this might magnetize the deck
causing noise and distortion during recording.
At time of writing, I do not know if this
can be fixed by using a head demagnetizer.
I therefore recommend that you do not use
magnetized screwdrivers anywhere close to
Lets get to work
- First thing you do is unplug your deck from
the mains power, as well as anything else.
Then, open the cabinet by removing the
screws on the sides, and remove the cover.
(optional: remove the bottom cover plate
from the cabinet, which will make it easier
to remove and return the mechanism later).
- Remove screw A, then unplug connectors B.
C, D (record/playback head) and E (erase
head, this connector is not on the main board,
but on the vertical board on the right).
Follow all the disconnected cables (that
all lead to the mechnism) and cut all tie
wraps that keep these cables in place. Make
sure that you don't accidentally cut any
wires when removing the tie wraps.
(Note: in the BX-100, connector D is turned
- Remove the little screw in the middle on
the upper side, and the two screws in the
bottom, as indicated in the pictures. This
will allow you to remove the mechanism later.
- Remove the counter belt from the counter
wheel, don't worry about how it's secured
on the other side.
(Note: this doesn't apply to the BX-150).
- Now take out the mechanism by pulling it
backwards. You might have to turn it a
Just experiment, but do not force anything!
After taking it out, move the cabinet to
some safe place, we won't be needing it
- We now have only the mechanism on our desk.
Remove the two black screws, and then remove
the back cover plate.
- This is what the front side of the mechism
looks like. Yours might actually look different,
showing a so called idler wheel with a rubber
tire on it. The idler wheel rubber tire is
a common cause of another problem (take-up
reels not turning properly), but it my deck
the idler system has been replaced with a
gear system during a repair. This gear system
became standard starting with the CR-1.
Now keep the mechnism level with your desk,
and remove the screw shown in the picture.
Next, open the cassette holder by pressing
the lever on the far left:
- Slide out the metal 'head base hold plate'
as shown in the picture, but make sure the
metal ball under it doesn't roll away.
- Using tweezers, take out the metal ball A,
next remove screw B.
- Close the cassette holder if it's open and
turn over the mechanism. Remove screws C
and D, and just give screws A and B some
slack by giving them two turns each, but
do not remove them. Then tilt metal plate
E with your left hand, and remove the cam
motor assembly with your right hand as indicated
by the arrow:
- Notice how Cam wheel (B) is positioned relative
to the leaf switches (A). After the motor
has been cleaned, the cam wheel must be returned
into this position, or it will get difficult
to return the cam motor assembly into the
Next, gently lift up the leaf switches
pull the cam wheel out:
(Note: the cam wheel might have a different
position in other models than the BX100/125/150,
so make sure you make proper note of it).
- Gently remove worm wheel C from the motor
axis by holding a slot screw driver between
the wheel and the motor case, pushing off
the wheel with the screw diver. careful,
or you might need to look for the wheel at
the other end of the room!
Next, remove screws A and B with the tiny
screw driver. Use a decent screw driver with
a handle that offers decent grip, to prevent
the screw heads from being damaged:
- Remove the mu-metal shield. You might have
to cut the label, and sometimes the mu-metal
sticks to the motor case. You might need
to apply a little force to get it off, but
it helps to turn it clockwise (or counterclockwise,
depending on how the mu-metal wasput on the
motor), so the strain is decreased. Be carefull
not to damage the wiring to the motor:
- Using the handle of a screwdriver, tap against
the case of the motor, and turn the axis
around a few times. This will loosen the
motor. Now using the 9 volt battery (or a
similar power source), let the motor runs
for a minute or so, so oxidation is removed
from the carbon brushes by means of friction:
- Using a tiny slot screwdriver, bend out the
two metal pins, one on each side, just enough
to be able to take the contents out of the
- Now this is very important:
DO NOT PULL OUT THE PLASTIC PART FROM THE
METAL CASE. THIS MIGHT RESULT IN THE CARBON
BRUSHES BREAKING OFF, RENDERING YOUR MOTOR
Instead, holding the metal case, push the
axis on a firm surface, thus pushing out
the contents from the case. When pushed out
as far as possible, take out the so called
rotor, still attached to the plastic base.
You might need to improvise here with a screwdriver:
- With a small screw driver, lift up one of
the metal pins (that hold the carbon brushes),
then gently take the rotor off the plastic
base, make sure you don't break anything
on the metal pin on the other side:
- Now that the rotor and the plastic base have
been separated, you can clearly see that
there is a lot of dirt on the contact surfaces.
You can probably imagine that spraying some
contact cleaner from the outside does not
perform a proper cleaning job.
Now spray a tiny bit of contact cleaner onto
the so-called commutator (as indicated by
the arrow), as well as onto the two tiny
carbon brushes (as indicated by the two little
circles). You can use Deoxit, Contact Cleaner
390 or Kontakt 60 for that. Now let it sit
for a couple of minutes and do its magic.
- Meanwhile, clean the cam and worm wheels
with a little water and mild soap and some
kind of brush (e.g. tooth brush), removing
old and dried lubricant, but only if you
intend to relubricate them later on. Make
sure you dry these wheels thoroughly.
- Using Q-tips, gently clean the commutator
of the rotor as well as the carbon brushes.
If you have used an agressive spray such
as Kontakt 60, please also rinse with Kontakt
WL spray first:
- Optional step: drill two tiny holes into
the plastic base, so it will be easier
spray some kind of contact cleaner into
motor, should that become necessary in
future. Be sure to drill the holes in places
that don't damage anything:
- The carbon brushes are worn by usage, and
therefore might apply less pressure on the
commutator. To make them apply more pressure,
bend each of the metal pin inwards to the
center using a srewdriver, as indicated by
the arrows. This will really make a difference:
- Now using a small screwdriver to bend one
of the metal pins a bit, gently put the rotor
back on the plastic base. After that, spray
a small amount of contact spray, either Deoxit,
Contact Cleaner 390 or even better Kontakt
61, on the commutator. (Note: NOT KONTAKT
60!). This will provide lubrication as well
as protection against oxidation. Then, return
the rotor into the metal case.
Before closing the motor, test it to see
it runs with the 9V battery, or another similar
power source. Let it run for a minute or
so, then reverse the battery polarity to
have the motor spin the other way. This will
'grind' the carbon brushes again:
- Using a slot screwdriver, close the motor
case by bending the two pins inwards:
- Return the mu-metal strip to the motor case:
- Next, we're going to clean the leaf switches
of the cam wheel. Spray a tiny amount of
contact cleaner onto the contacts (be sure
not to spray on anything else, such as the
cam wheel axis), and let it work its magic
for a couple of minutes:
- Drench a piece of cardboard paper in contact
cleaner, and rub it between the switches.
After that, remove all dirt and cleaning
spray residues by gently rubbing a Q-tip
between the switches, it helps if you also
moisten them with cleaning alcohol. Then
again spray a tiny amount of contact cleaner
(Deoxit, Contact Cleaner 390 or Kontakt 61,
but not Kontakt 60) onto the contacts:
- Next, reassemble the cam motor assembly by
pushing the worm wheel onto the axis and
screwing the motor onto the assembly. Then,
apply a little lubricant to the cam and worm
- Return the cam wheel(B) to the assembly,
making sure it's in the right position.
will need to gently lift the leaf switches
(Note: this picture shows the proper position
for the BX100/125/150, but other models might
require other positions).
- Return the cam motor assembly to the mechanism.
Axis A needs to go in hole B. You might need
to play around with it, sometime the axis
will not go into the hole easily. If all
goes well, the cam motor assembly is securely
in place. Make sure no wires get stuck under
one of the metal plates:
- Returns screws C and D, after that tighten
screws A and B:
- Turn over the mechanism and using Q-tips
remove all the lubricant that has been getting
stale there for some 20 years or more. Then
apply a small amount a fresh ball bearing
grease. It's not well visible in the picture,
but there is probably a little line worn
in by the little metal ball:
- Return tiny screw A, then holding the mechanism
level to your desk, return the metal ball
B just to the right of the worn line. The
ball bearing grease will most likely hold
- Still holding the mechanism level, return
the head base hold plate (A) by sliding it
back in, in such a way that the metal ball
is grabbed by the open space in the plate.
Then return screw B:
- Open the cassette holder and return the cover
plate into position. Make sure it doesn't
stick out at the bottom, as indicated by
the picture. After that, return the two black
screws at the top of the cover plate:
- Grab hold of the deck's cabinet and return
the mechanism in there. While you slide in
the mechanism, hold the counter belt with
one hand, so you can easily return it to
the counter wheel:
- Do not yet screw the mechanism into place
yet. Instead, reconnect connectors B and
C to their sockets, but not yet connectors
D and E. Also, make sure the wire that is
supposed to be screwed to position A is not
in contact with anything that might cause
a short circuit.
Then, connect the power cord to a power outlet,
but make sure you do not touch anything inside
to prevent electric shock. Now turn the deck
on by pressing the power button. If it starts
producing unexpected sounds, lights or fumes,
immediately switch it off again and try to
figure out what went wrong (I can't help
you with that one though). But if nothing
unexpected happens, press the play button:
if the cassette holder is closed, the deck
should now come to life! Congrats! Experiment
a bit by going from play to pause, stop,
rewind etc.etc. To test record mode, you
will need to insert a recordable cassette.
Next, switch off power and disconnect the
power cord. Reconnect the R/P head cable
connector to socket D and erase head cable
connector to socket E. Return the grouding
cable to position A using the appropriate
If you wish, you can organize the cables
in the deck using tie-wraps.
- Secure the mechanism by returning the three
screws that hold it in place. Close the cabinet
with the top cover and, if you removed it
at some stage, the bottom plate.
- That was all. Now clean the heads, capstan
and pinch roller, demagnetize them if you
own a head demagnetizer.
- Happy playing! I recommend that you operate
your deck frequently, if only for the purpose
of keeping the cam motor carbon brushes from
oxidizing again. You don't actually have
to listen to music, just press play/stop
a few times.
- Andy’s repairs: cr7 control motor: similar procedure for the CR-7 deck, only
Andy doesn't take his cam motor apart. I
integrated some of his ideas into my instructions,
my gratitude to Andy for that.
- Scott's Nak FAQ: rich resource of technical information
of Nakamichi decks.
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© 2012 Pieter Mol
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