2024-12-29 - Replacing Belts in a Panasonic RX-FW29L Cassette Recorder
----------------------------------------------------------------------

Years ago, I got an old Panasonic RX-FW29L cassette recorder that has
just been lying around collecting dust ever since[0]. It was still in
working condition, at least partially. The left side worked without
any problems, but on the right side, the spools weren't turned, so
the tape wasn't pulled back into the cassette. I figured there was
probably a bad belt somewhere inside, so I decided to take it apart.

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

WARNING: This device does plug directly into mains power, so make
sure that you don't electrocute yourself. If you don't know how to
stay safe when working on such a device, please don't kill yourself
and let someone else do the work instead.

The first step is to remove all the screws on the back[1], including
the ones inside the battery compartment[2]. I also removed the
antenna[3], but I think that wasn't actually necessary. [4] shows all
the screws that came out. Note that one of them is a bit shorter,
so take care to put that one back into the correct place (I forgot
which hole that one belonged to, but it should be obvious if you have
to take the same cassette recorder apart).

Once all the screws have been removed, it is possible to take
off the entire front of the recorder[5] (both cassette doors have
to be open for that to work). The front is held on by two cable
bundles[6][7] which have to be unplugged in order to remove it
completely[8]. The carrying handle[9] can also be slid out once the
front has been removed.

In order to remove the mechanism, the red plastic on the right
side needs to be removed first[10]. Two of the screws are readily
accessible, but one is hidden behind the tuning wheel at the top,
which makes it a bit annoying to unscrew. The tuning wheel needs to
be removed together with the board it is attached to[11]. There is a
hole in the board through which a plastic piece can be pushed down to
allow the board to slide out[12]. This part is quite annoying because
the board is wedged in very tightly. Once the board with the tuning
wheel and the screw behind it have been removed, the red plastic piece
can finally be moved to the side[13].

Once that is gone, four screws in the mechanism must be removed[14][15]
and the black plastic piece on the left side underneath one of the
screws must be taken out[16]. This allows the mechanism to be partially
taken out, although it is still held by four cables[17]. Take note
of the gray cable at the right because it needs to be put back the
same way it was before during reassembly[18]. At this point, I could
already see the bad belt, or rather, the lack thereof[19]. The remains
could be seen lying at the bottom[20]. In order to fully remove
the mechanism, the cable bundles need to be unplugged. The gray
and black bundles on the right are also glued in[21], but the glue
can simply be broken off (I don't think the glue is too important,
so I didn't add any fresh glue during reassembly). The mechanism can
then be taken out completely[22]. Note that there is a spring on one
of the wheels (the one where the belt was missing/destroyed), which
will fall out when taking the mechanism out[23]. In the picture,
it is the wrong way around, but more on that later. I think this
wheel is the slipping clutch that is used to turn the spools at the
correct speed[24] (the two parts of the wheel are pushed together by
the spring, with a piece of felt in between), but I'm not an expert,
so I'm not entirely sure about that.

Belt Replacement
----------------

Since the old belt had completely disintegrated and there was still
some sticky residue left on the wheel, I had to clean that off before
the new belt could be inserted. Cleaning the second wheel that the belt
wraps around was a bit difficult because it's located underneath the
big metal wheel. I fortunately managed to find a matching belt in my
collection of random belts. I forgot to measure its circumference, but
I did note down that it was a square belt with a thickness of 1mm
(don't take my word for it, though, because my notes weren't
particularly great, and I'm not entirely sure if I interpreted them
correctly when writing this article). If you need to buy a replacement
belt and don't have a reference for it, you could probably take a piece
of string and lay it around the wheels to figure out what the
approximate circumference should be, then buy a belt with the proper
thickness and a circumference slightly less than what was measured with
the string (so it isn't loose).

In order to replace the belt, the belt going around the larger wheel
has to be removed first[25], after which the replacement belt can
be inserted[26]. It's a bit difficult to get the belt underneath the
large wheel because there are some obstacles in the way, so you need
to poke around quite a bit before it sits properly.

The belt around the larger wheel seemed to be fine still, so I left
that alone, but there was a belt on the other side of the mechanism
that was already a bit loose[27]. It still worked, but since I had
everything disassembled already, I decided to replace it as well
(mainly because I got a collection of belts a while ago, so I didn't
have to buy any replacement). The mechanism needs to be turned
around to access the small plastic wheel that this belt is wrapped
around[28]. There are two smaller belts which can be seen on that side
of the mechanism, but those are only used to advance the tape counter,
so I didn't replace them even though they were fairly loose.

UPDATE (2024-12-30): Just to clarify, the tape counter is still
working, the belts are just a bit loose. I don't think the loose
belts are much of a problem in this case, though, because they only
have to move a tiny wheel for the tape counter.

Mechanism Reassembly
--------------------

Once the belts have been replaced, the mechanism can be reattached
to the rest of the cassette recorder. Make sure to reattach the four
cables, and put the black and gray cables on the right side into the
correct places again where they were originally glued. Particularly
watch out that the gray cable goes back as shown in [18] before
screwing the mechanism back in. Another important note is that the
spring which was mentioned earlier needs to go into the correct
place. I originally put the larger side onto the plastic wheel[29],
but that caused the spring to rotate with the wheel and cause clicking
sounds[30]. Turning it around resolved those issues[31][32]. When
reattaching the red plastic piece on the right side, it's quite
difficult to push the board with the tuning wheel back in. I used a
screw driver to push down on the little plastic clip so the board
was easier to push in, but it still required a lot of force[33]
(of course, only do that after screwing in the screw that is hidden
behind the tuning wheel).

Volume Slider and Carrying Handle
---------------------------------

Before reattaching the front part of the cassette recorder, it might
be helpful to look at the volume slider on the left side, which was a
bit scratchy in this device. It is an interesting sort of potentiometer
because the resistive track is visible from the outside, there is no
cover over it[34]. In this case, that was somewhat convenient because
it meant that I could clean it reasonably well without having to take
out the entire circuit board it is attached to. I cleaned it with
isopropyl alcohol and added some silicone grease[35], as explained
in one of my previous articles[36]. Adding the grease might have
been a bad idea since the missing cover on the potentiometer means
that more dust might get stuck on the grease, but I can't say for
sure. Don't forget to stick the plastic slider back on after cleaning
the potentiometer[37].

One last issue I noticed was that the plastic holding the carrying
handle was broken partially, so I glued that back on[38]. I don't
think it really is critical, though, since the front of the cassette
recorder slides over the top and prevents the carrying handle from
breaking out completely[39].

Final Reassembly
----------------

There isn't really much left to be said now. Just make sure to
reattach the two cable bundles from the front part before putting it
back on. One last tip is that it's best to push the top in first so
the buttons there go through the holes in the front part, and then
push the rest in[40].

I think that's all I had to say. Have fun repairing obsolete devices.


[0] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/recorder.jpg
[1] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/back.jpg
[2] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/battery_screws.jpg
[3] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/antenna.jpg
[4] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/screws.jpg
[5] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/half_open.jpg
[6] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/front_cables1.jpg
[7] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/front_cables2.jpg
[8] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/open.jpg
[9] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/carrying_handle.jpg
[10] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/red_plastic.jpg
[11] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/red_plastic_board.jpg
[12] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/red_plastic_board_removed.jpg
[13] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/red_plastic_removed.jpg
[14] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_screws1.jpg
[15] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_screws2.jpg
[16] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_black_plastic.jpg
[17] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_removal.jpg
[18] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_gray_cable.jpg
[19] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/missing_belt1.jpg
[20] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/missing_belt2.jpg
[21] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_gray_cable_glue.jpg
[22] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_removed.jpg
[23] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/mechanism_spring.jpg
[24] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/slipping_clutch.jpg
[25] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/belt_replacement1.jpg
[26] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/belt_replacement2.jpg
[27] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/other_belt.jpg
[28] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/belts_other_side.jpg
[29] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/spring_wrong.jpg
[30] gopher://lumidify.org/9/phlog/2024-12-29-cassette-recorder/spring_wrong.ogv
[31] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/spring_correct.jpg
[32] gopher://lumidify.org/9/phlog/2024-12-29-cassette-recorder/spring_correct.ogv
[33] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/red_plastic_board_reattachment.jpg
[34] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/volume.jpg
[35] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/volume_greased.jpg
[36] gopher://lumidify.org/0/phlog/2023-10-15-speakers.txt
[37] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/volume_slider.jpg
[38] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/carrying_handle_broken1.jpg
[39] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/carrying_handle_broken2.jpg
[40] gopher://lumidify.org/I/phlog/2024-12-29-cassette-recorder/front_reattachment.jpg

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