siliconchip.com.au Australia’s electronics magazine June 2019 65
the other getting in the way.
I began with the left-hand pod, as
this is where the main audio cable
enters and any electronics should be
located inside it.
After removing the outer earpiece
ring, there were three longer screws
underneath holding the two shells of
the can together. Once the screws were
out, the two halves easily separated.
Inside was a sizeable PCB containing
what I assumed to be an amplifier and
a USB decoder.
The 3m long main cable enters the
bottom of the pod through a plastic
strain-reliever and sports USB and
3.5mm jacks (one 3.5mm stereo jack
for sound input and another mono jack
for microphone output) at the far end.
A second, much thinner cable exits
the top of the can through a grommet
and heads off through the headband
to the other pod.
The shielded main cable contains
eight tiny wires, and the thinner cable
has three, all colour-coded and termi-
nated to their respective solder pads
on the PCB. Or perhaps I should say,
they should be terminated; I could
see three wires floating happily in the
breeze, while the others looked to be
tack-glued to the PCB with large, dull
solder blobs.
Whoever put this together should
go back to soldering school. It was a
wonder it worked at all!
Before doing anything, I had to fig-
ure out which wire went where on the
PCB. As is typical on cheap electron-
ics, there was no information screen
printed onto the board. Usually, if
leads break free, they are relatively
easy to match using a microscope and
a basic comparison with their distinc-
tively broken ends; if just not connect-
ed properly, this can be a bit trickier.
Luckily, in this case, I could match
each wire to an impression in the sol-
der blobs enough to make an educat-
ed guess.
The type of wire used in the ca-
bles is prevalent in audio gear.
Each multi-stranded wire is
very fine and well-insulated,
but not by an obvious plas-
tic coating like other types of
wire. Each wire also has very
fine cotton or synthetic threads
running through it, likely for
strain relief, which along with
the insulation material makes
soldering it a real challenge.
Even with a decent amount
of heat, solder just beads and runs off.
No wonder it was just globbed together
at the sweatshop, er, I mean factory.
In the past, I’ve had to burn the in-
sulation off to be able to solder it. In
the early days, I used a match; now,
I use a small gas torch, the kind used
for jewellery or micro-welding. A brief
touch to the end of the wire causes
the thread and insulation to instantly
burn off. A quick pinch with a damp
sponge removes any crispy remains,
leaving shiny wire behind.
While solder sticks to this cleaned
surface, I also use a touch of flux to
help it ‘sweat’ through.
While I was at it, I also re-soldered
the other connections, prepping and
cleaning wires and PCB pads before
tinning them all with fresh solder. It
was simply a matter of a quick touch
with the iron to re-connect everything
and a sound-check confirmed I had
audio in both cans and a working mi-
crophone.
Reassembly was as easy and pull-
ing them apart, and I still use these
’phones today. Not exactly Bingles, but
OK for cheap Chinese imports.Digital photo frame repair
B. P., of Dundathu, Qld is another
person who is willing to put in a lit-
tle bit of effort to fix a device, even a
fairly cheap one, rather than throwing
it away and buying a new one. And as
he says, sometimes the faulty compo-
nent is obvious and the repair is not
too difficult. You just need to be will-
ing to have a go...