2025-04-10 - Partially Fixing a Tevion MD4759 CD Player
-------------------------------------------------------

I got an old Tevion MD4759 CD and cassette player[0] a while ago that
wasn't working properly. The cassette player was actually working
fine, but the CD player didn't do anything, the CD wouldn't even spin
when it was inserted. While playing around with it, I noticed that it
would start working if I tilted it to the side. [1] seemed to suggest
that the spindle motor might be bad, but it could possibly be fixed
by oiling it. I also want to point to [2] because it contains a lot
of useful information about motors in CD players. This particular CD
player isn't a very high-quality one, and I have absolutely no use
for it, but being who I am, I had to open it up and try to fix it.

WARNING: This is a mains-connected device. Do not open such devices
if you do not know what you are doing as it can potentially cause
death or injury.

Disassembly
-----------

There are screws on the back of the unit that need to be unscrewed
to open it[3]. There should be 7 in total, including one inside the
battery compartment[4]. I also marked the screw holding the antenna
in that image, but as far as I remember, that doesn't need to be
removed to open the device. Once the screws have been removed, the
front part can be separated from the back part[5] (I think the CD
player had to be open for this to work properly, but I'm not sure
anymore). The front part is still connected to the back part with
several cables. Two cable bundles going to the cassette player can
simply be unplugged[6], although they are plugged in very tightly and
aren't too easy to get out. I used needle-nose pliers and flat-headed
screwdrivers to get them out, but it was still difficult and I almost
damaged the plugs in the process. Unfortunately, some other cables
are soldered directly and even covered in glue[7], so I didn't want
to remove those. Still, after the cables going to the cassette player
are unplugged, the front part can be put aside fairly well because
the soldered cables are only on one side[8].

The next step is to remove the circuit board from the plastic
case. First, two screws at the back need to be removed[9]. These hold
the part of the plastic frame that the circuit board is screwed to,
so it can then be lifted away at least partially from the rest of the
plastic frame in order to reach all the screws on the circuit board. As
can be seen in [10] and [11], there are some screws in fairly hard to
reach places, so the the circuit board needs to be lifted up together
with the part it is screwed to in order to unscrew them. The only
problem is that there are a lot of soldered and glued cables that
don't allow too much movement, but they allow just enough movement to
get to the screws. I did break one cable off from where it was glued
in order to allow the circuit board to move more freely[12]. [13]
shows that same cable with some screws in the background that also
need to be removed. The screw with an "X" over it doesn't need to be
removed because it only connects the secondary circuit board in front
with the one in the back, and both need to be removed together. In
total, there should be 14 screws that have to be removed, 12 on the
big circuit board and 2 on the small one in the front.

There are now three cable bundles/ribbon cables going to
the CD drive that need to be unplugged from the small circuit
board[14][15][16]. These are somewhat difficult to get to, and they're
also plugged in pretty tightly. I had some luck using a screwdriver
to loosen one of them[17], but it still was very annoying. The
small socket for the plug with only two cables is also very easy to
bend because it is only connected to the board with the two solder
joints[18]. Once these cables have all been unplugged, one plastic clip
holding the large circuit board has to be pushed away[19] before the
two circuit boards can finally be removed[20]. Note that I unplugged
the ribbon cable on the side of the CD drive. When I took the CD player
apart again later, I unplugged it on the other side, but I'm not sure
which way is easier. There are still cables connecting the board to
the speakers in the plastic frame, but at least it can be removed
far enough to access the CD drive (the speakers can be unscrewed, but
that wasn't necessary). The CD drive is held on by 4 screws. Since the
circuit boards were somewhat in the way still, I stuck a screwdriver
through the gap between the two boards to get at the bottom two
screws[21]. The CD drive can then finally be removed completely[22].

Spindle Motor Oiling/Replacement
--------------------------------

The spindle motor in this device is a Mabuchi RF-310T-11400[23]. I
first tried to oil it a bit by adding a drop of sewing machine oil
around the bearings[24] and letting the motor run for a bit using my
benchtop power supply. However, this didn't help at all, even though
the motor seemed to run perfectly fine when I powered it myself. At
this point, most people wouldn't want to waste any more time and
money on such a CD player. Luckily, I'm stupid and spend my money
on useless things, so I decided to go ahead and buy a replacement
motor. Fortunately, I found exactly the same model online for
around 10€. I'm sure it would be possible to find other compatible
replacement motors, but I don't have enough experience to properly
match all the important characteristics, so it was good that I found
the same model. Do note that there seem to be motors with exactly
the same model number but a different shaft length. For instance,
in this CD player, the motor driving the laser assembly had exactly
the same model number, but a shorter shaft length.

In order to replace the motor, the spindle platter first needs to
be removed from the old one. Before doing that, the height should
be measured carefully so the platter can be placed at the correct
height on the new motor. I measured both the height of the platter
over the plastic frame beside it[25] (exactly 1mm) and the height
from the tip of the motor shaft to the top of the middle part of the
platter[26] using calipers. I ended up not using the second
measurement, though, because I realized that it was kind of pointless
since the important part is how far the CD is above the laser, and
that was measured by the first measurement. [27] suggests to use a
folded piece of paper as a shim underneath the platter so it can
simply be pushed down to the height of the paper, but this didn't
work in my case because the bottom of the platter was at approximately
the same level as the top of the plastic frame, so it was impossible
to push a paper between it and the frame[28].

I first tried to pull the platter off directly, but that didn't
work. Following a suggestion I found somewhere (I forgot where
exactly), I heated the motor shaft and platter up a bit. I used my
hot air station, set to 300 degrees Celsius, but that was a fairly
random temperature[29]. Even though I only heated it up very briefly
(so I could still easily touch both the shaft and the platter), that
still helped a lot. It was still difficult, but I managed to pull the
platter off just by pulling it with my fingers[30]. It did come off
very suddenly, so be careful that nothing else gets damaged. I couldn't
find any better way to get it off because prying with any tools would
probably cause too much damage. Also, it probably is a good idea to
move the laser assembly to the other side first so it is as far away
from the spindle as possible in order to avoid damage to it.

Both the spindle motor and the motor driving the laser assembly have
to be unscrewed because they are both soldered into the same circuit
board[31] (the screws for the spindle motor are slightly hidden here
because I took the picture before removing the platter). Once this is
done, the motors can be placed on a professional motor holder[32] in
order to desolder the old motor and solder the new one in (make sure
to put it in the right way so the positive and negative terminals are
at the right positions). Getting the platter to the correct height
wasn't particularly easy. I repeatedly pushed it in and pulled it
out again (after heating it with my hot air station), until it was at
approximately the correct height[33]. Fine adjustment wasn't really
possible without better tools.

Reassembly
----------

Reassembly is mainly the same as the disassembly, just the other way
around, but there are a few parts I wanted to draw attention to.

It can be somewhat annoying to screw the CD drive back in because
the screws are surrounded by rubber pieces, probably to soften
vibrations[34], which means that the screws are fairly loose and don't
always line up with the screw holes properly, so some fiddling around
is needed for everything to work. Another annoying part is plugging
all the cables back in. I later noticed that I did one thing wrong
when plugging in the ribbon cable going to the laser assembly. When I
plugged it in, the laser assembly was nearest to the spindle motor[35],
but that meant it was as far away from the other end of the ribbon
cable as possible, so it would have made much more sense to move it
to the other side in order to make plugging the cable in easier.

There were also some cables that had to be routed properly before
the circuit board could be put in properly, but I can't remember
which ones exactly they were. I do remember that there were some on
the right-hand side[36] that liked to get caught on the wrong side
of plastic parts, but the only real advice I can give is to fiddle
around with the circuit board a bit until everything fits. The other
inconvenient thing is that some of the buttons from the top panel fall
out when the circuit board is gone, so they have to be put back again
before screwing the board in[37]. Lastly, I attached the orange cable
again where I broke the glue. I didn't actually use new glue, I just
pushed it back where the old glue was since it probably wasn't really
too important for this one cable to be attached there anyways[38].

Side note: At some point, I got very confused because the player
wouldn't turn on at all anymore, none of the buttons gave any
reaction. After more time spent debugging than I would care to admit,
it turned out that the problem was just that I was stupid. There is
a DC/AC switch on the back to switch between AC power and DC power
from the battery compartment, and I must have accidentally switched
that to DC mode at some point[39].

Testing and Laser Mechanism Greasing
------------------------------------

Once I had reassembled the device far enough to test the CD player,
I tried playing a CD. Now it worked, so the problem really was
the motor. However, there still was another problem. Even though
regular playing worked, if I tried to skip too many tracks at once,
the laser would start seeking all over the place, and eventually the
player would go into an error state. I decided to grease the laser
mechanism to see if that would change anything. It didn't help in
the end, but I decided to still share the process here (and yes, I
did try cleaning the laser first, but that didn't help either).

The metal bar that the laser assembly slides on is held on by
plastic pieces on one end that can be pushed away to remove
it[40][41]. Removing this bar isn't strictly necessary, but it
makes it possible to properly clean off the old grease, particularly
inside the plastic parts that slide on the bar. The gears that move
the laser assembly can be removed by first unclipping one gear and
the cover over another gear on the bottom[42][43], after which the
remaining gear can simply be pulled off. One of the gears didn't
have any grease on it. I'm not entirely sure why that was the case,
but I decided to only clean and grease the other gears since there is
sometimes an important reason why a particular gear is not greased. I
also added some new grease to the metal bar[45], although I had to
remove some excess grease again after moving the laser assembly back
and forth a few times[46].

As mentioned before, this didn't actually help with the problem, so
skipping too many tracks at once was still impossible. Maybe the motor
driving the laser assembly had also become slightly weaker with age,
or maybe there was a totally different issue (could it even have been
caused by the platter not being at the perfect height or the laser
assembly being damaged in some way?). As unfortunate as it was, I
decided to stop here because I didn't want to order another new motor,
and frankly, I'd had enough of this CD player at that point. It would
have been nice to figure out the problem, but at least it was still
possible to play CDs normally, as long as not too many tracks were
skipped at once.

Bonus: Taking Apart the Motor
-----------------------------

I decided to take apart the old motor, just for the fun of it. This
wasn't nearly as easy as it sounds because the bottom plate was held
on by several tiny metal clips[47]. It took a lot of messing around
with pliers[48] until I could finally pry the plate off[49]. Inside,
the motor actually looked surprisingly clean[50]. I don't really know
what caused it to stop working properly in the CD player. Maybe the
brushes were just a tiny bit dirty and thus didn't conduct as well
anymore, causing the motor to be a bit weaker? Or were the bearings
at fault and the sewing machine oil didn't help? One thing I noticed
is that the sewing machine oil didn't seem to really have stayed in
the bearings, it probably had too low of a viscosity and was flung
out when the motor turned. Another thing I noticed is that the old
motor sounded a little bit different than the new one when I ran it
with my benchtop power supply, almost a bit "softer" in a sense, but
I'm not sure if that difference was really significant. I can't say
for sure what the problem was, I just know that the new motor worked
in the CD player, so something must have been wrong with the old one.

I decided to clean the motor a bit with isopropyl alcohol[51][52]
and then grease the bearings, even though I will probably never have
any use for it (I used grease instead of sewing machine oil this time
since I could access the bearings properly and I wanted something with
a higher viscosity). Reassembly is a bit fiddly because the brushes are
in the way of the shaft when putting the parts together[53]. Also,
the bottom plate isn't held on as well anymore because I kind
of destroyed the metal clips during disassembly. The motor worked
properly afterwards, but I couldn't really tell if it worked any
better than before, and I didn't feel like disassembling the entire
CD player again just to test this motor.

Conclusion
----------

This was another one of those repairs that really didn't make much
sense because I spent a lot of time (and even some money) on a device
that wasn't worth much, and I couldn't even fully fix it. Still, I
learned a lot about CD players, so I guess that's somewhat useful. I
ended up giving the player away to a person who only needed a cassette
player, so at least that part is being used now.


[0] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_player.jpg
[1] https://stereo2go.com/forums/threads/cd-runs-only-when-tilted-panasonic-rx-dt9.6417/
[2] https://www.petervis.com/CD_and_DVD_Players/cd-player-motor-not-spinning/cd-player-motor-not-spinning.html
[3] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/back.jpg
[4] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/back_screws.jpg
[5] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/half_open.jpg
[6] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cassette_cables.jpg
[7] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_glue.jpg
[8] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/front_off.jpg
[9] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/top_part_back_screws.jpg
[10] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/circuit_board_screws1.jpg
[11] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/circuit_board_screws2.jpg
[12] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_glue_removed1.jpg
[13] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_glue_removed2.jpg
[14] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_cables1.jpg
[15] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_cables2.jpg
[16] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_cables3.jpg
[17] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_plug_loosening.jpg
[18] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_socket_bent.jpg
[19] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/circuit_board_clip.jpg
[20] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/circuit_board_removed.jpg
[21] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_unscrewing.jpg
[22] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_removed.jpg
[23] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_motor.jpg
[24] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_motor_oiling.jpg
[25] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_height_measurement1.jpg
[26] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_height_measurement2.jpg
[27] https://www.repairfaq.org/REPAIR/F_cdfaq8.html#CDFAQ_007
[28] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_height_measurement3.jpg
[29] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_heating.jpg
[30] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_removed.jpg
[31] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_screws.jpg
[32] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_holder.jpg
[33] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/spindle_reattached.jpg
[34] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_screws.jpg
[35] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cd_drive_ribbon_cable.jpg
[36] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_routing.jpg
[37] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/buttons.jpg
[38] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/cable_glue_reattached.jpg
[39] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/power_switch.jpg
[40] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_metal_bar.jpg
[41] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_metal_bar_removed.jpg
[42] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_gear_clips.jpg
[43] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_gears_removed1.jpg
[44] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_gears_removed2.jpg
[45] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_metal_bar_greased.jpg
[46] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/laser_metal_bar_excess_grease.jpg
[47] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_disassembly1.jpg
[48] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_disassembly2.jpg
[49] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_disassembly3.jpg
[50] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_disassembled.jpg
[51] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_cleaning1.jpg
[52] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_cleaning2.jpg
[53] gopher://lumidify.org/I/phlog/2025-04-10-cd-player/motor_reassembly.jpg