2024-06-22 - Fixing a Cheap Flashlight
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Welcome to another article in the series "repairing things that any
sane person would throw away". This time, our subject of study is a
cheap flashlight that I got 8 or so years ago[0]. The problem with
this flashlight was that the switch would always stay stuck in the
"off"-position, so you had to try quite a few times until it would
finally turn on. After living with this problem for years, I finally
decided to take a closer look.

Getting to the actual switch isn't very difficult, but it does require
a bit of brute force. Unfortunately, I didn't take any pictures while
disassembling the flashlight, but the pictures of the reassembly should
be helpful. The switch is located in the bottom part that is unscrewed
to change the batteries. First, the rubber cover over the switch had
to be removed.  Then, the plastic inside the metal case needed to be
pushed out. This required a bit of force, and I had to make sure not
to push directly on the switch, but rather beside it. Eventually,
the entire plastic piece holding the switch popped out, and I could
remove the actual switch from it.

The switch itself could just be pried open, but the contact covering
the back had to be bent a bit so it wasn't in the way. Inside, the
mechanism works with two plastic pieces that are pushed by a spring
and change their configuration when the switch is pressed so they
either push the round metal piece away from the two contacts or let
it touch them[1]. The problem was that the inner plastic piece which
was touching the metal piece was broken[2]. I first tried to glue
just the plastic piece, but that didn't work because there was not
enough area for the glue to work properly. I then decided to glue
it together with the metal piece. The problem was that there was a
small gap between the plastic piece and the metal piece, making it
difficult to glue properly (this is probably the reason why it broke
in the first place - all the force was on a very small area because
there was no contact between the larger flat part of the metal piece
and the plastic piece). I spent some time looking for a thin washer
to place between the pieces and finally realized that I could just
take a part from an old laptop hinge[3]. I then glued the pieces
together with two-component epoxy glue and placed them in my highly
professional clamp[4].

Unfortunately, the washer was a tiny bit too thick, so the gap was now
too large even in the "on"-position[5]. Luckily, I found a metal piece
from an old laptop lying around on my desk with two small holes in
it[6]. After cutting out two small parts from this, enlarging the holes
slightly, trimming the edges, and bending one side over to make them
slightly thicker, I had metal pieces to place underneath the actual
contacts to bridge the gap[7]. I could then start with the reassembly,
first by adding the plastic pieces and contacts back in[8]. The plastic
pieces in the middle need to be placed at different rotations. I first
placed the outside piece with the larger "teeth" pointing at the four
sides of the switch, and then placed the inside piece (with the round
metal piece glued to it) with the larger teeth pointing at the four
courners. That configuration is the "on"-position for the switch.

After adding the back cover of the switch, I could start with the
reassemly of the actual flashlight[9]. The round, black plastic piece
needs to go into the metal part of the flashlight with the rim in
the middle pointing outside. The switch needs to be pushed into the
white plastic part with the contact on the bottom making contact
to the spring inside the white part[10]. Then, brute force needs
to be used again to push the plastic assembly into the metal part,
with the switch pointing towards the outside[11].  I didn't have any
better tools than pliers and screwdrivers, but it would have been
ideal to have some hollow, round tool to evenly exert pressure in a
circular shape.  My method worked, but left some marks on the plastic.

I realized at the end that I had forgotten to add the rubber cover over
the switch[12].  It would have been ideal to add that already while
reassembling, but it was relatively easy to just push it in[13]. After
adding some fresh batteries (rechargeable, of course, because all
the cool kids use rechargeable batteries), I could finally test that
everything worked[14]. The switch still doesn't feel entirely right,
but it works much better than before. One reason for the wrong feeling
might be the glue residue left on the outside of the plastic piece
inside from my first attempt to glue it. Still, the flashlight works
properly again, so that's only a minor issue.

[0] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/flashlight.jpg
[1] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/switch_opened.jpg
[2] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/switch_broken.jpg
[3] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/washer.jpg
[4] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/clamp.jpg
[5] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/gap.jpg
[6] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/laptop_piece.jpg
[7] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/gap_fill.jpg
[8] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/switch_contacts.jpg
[9] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/reassembly_pieces.jpg
[10] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/reassembly_switch_mounting.jpg
[11] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/reassembly_brute_force.jpg
[12] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/reassembly_bottom.jpg
[13] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/reassembly_bottom_rubber.jpg
[14] gopher://lumidify.org/I/phlog/2024-06-22-flashlight/flashlight_on.jpg