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SERVICEMAN’S LOG
Use the force, Dave
Dave Thompson
Over the years, I have built and repaired some weird and wonderful
things. These items are not necessarily electronics-related, either. But none
of that prepared me for what showed up on my workbench this month.
F
or example, I have built a car from the ground up. I have
made my own furniture, musical instruments (many,
many guitars, mandolins and violins) and solid-state and
valve amplifiers to make the instruments louder.
I have made my own microphones, bugs, radios, computers, Theremins and myriad other hobby electronics projects
in between, mainly described by the likes of Electronics
Australia, Silicon Chip, Electronics Today International
and all the British magazines of the 1970s and 1980s. I have
also repaired hundreds, if not thousands, of devices, from
mechanical repairs to purely electronic fixes.
As you can imagine, this has been far more rewarding
than merely being an IT guy, though that business has
allowed me to indulge in all those other things. I have
repaired TVs and VCRs in Australia (which gives you an
indication of when I was there last!) and computers and
various other devices in England, Austria and Croatia. Still,
in all my years of doing this work, I have never repaired
a lightsabre!
I know. I can hear your gasps of excitement from here!
But, full disclaimer, and somewhat sadly, I must advise that
these are not ‘real’ lightsabres. I can hear your groans of
disappointment from here.
Real lightsabres are
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Silicon Chip
military-grade, highly classified and, as such, are very
closely monitored by the government because those things
can be really dangerous! If one isn’t careful, someone could
lose a hand! The purple ones are especially hazardous and
must be treated with great caution.
These two in the workshop are just civilian-level lightsabres. Even if modified (which I would never do, of course),
they will not take a leg off, cut burning swathes through
spaceship hulls or slice open the belly of a tauntaun on
the frigid surface of ice planet Hoth.
I know this is disappointing to many, but they are only
for training purposes, and are designed to avoid the catastrophic injuries typically associated with the real ones.
Toys vs the real deal
Many of you will have seen these toys in the stores
and may have even bought some for the grandkids. Generally, they are nasty, lightweight, cheap plastic things.
The best they do is flash a few LEDs down the soft translucent plastic tube that is supposed to be the ‘sabre’ part
of the device.
A few even make it look as if the blade ‘grows’ longer
by using strip lights, an effect that usually only works in
complete darkness and with a lot of imagination thrown
in. Typically, kids have these things bent and broken in
minutes because it is almost impossible to resist the urge
to smash them against each other (if two are available) or
into household furnishings.
This generally destroys them pretty quickly, because
they are not designed for that sort of action (even though
it’s the first and only thing a kid will want to do when they
get hold of one).
I remember being in a play at primary school wherein I
was cast as a pirate. Dad made me a sheet aluminium ‘cutlass’ style sword with a timber dowel and insulation-tape
handle to use as a prop. He warned me that it was pretty
weak around the tang (he used the word handle), so I
shouldn’t hit anything with it. You already know what I
did, the first chance I got.
In my defence, it’s a natural human reaction. Of course,
I hit something and sheared off the blade from the handle
on the first strike. He wouldn’t make me another one, so I
learned a lesson that day. I did the play with a plastic one,
and keenly felt the difference and his disappointment!
So, there’s a massive difference between the lightsabres
on the market. Some are for kids and don’t/won’t last, while
others are a little more adult, better thought out and might
actually make the grade.
Australia's electronics magazine
siliconchip.com.au
Items Covered This Month
• Stress testing your electronics
• Shining a light on an intermittent LED magnifier
• The beeping and oscillating fan
• Repairing a gifted extension lead
Dave Thompson runs PC Anytime in Christchurch, NZ.
Website: www.pcanytime.co.nz
Email: dave<at>pcanytime.co.nz
Cartoonist – Louis Decrevel
Website: loueee.com
Nicely made but not robust
The two that turned up in my workshop recently were
of the latter variety. These devices were heavy-duty and
very well made, the best I have ever seen. They hailed from
China (where else) and were not overly expensive, given
their build quality.
The handles were substantial and hefty, about 200mm
long and 25mm in diameter. They were made from beautifully turned thick aluminium stock, anodised in black. A
small speaker was mounted within the tube handle right
at the bottom, protected by a fine steel mesh.
If you can recall those ultrasonic transducers we used to
experiment with back in the 80s, you’ll be able to picture
what this speaker looks like from the bottom. At the other
end, a very shiny parabolic-shaped reflector is embedded
in the top end of the handle. This contains a super-bright
LED array, in monolithic form, mounted right in the centre.
Along the top of the handle, where your thumb would
naturally sit, is a solid push button, which switches the
device on and off. Just below that is a charging port, a
standard barrel connector that uses a lead (which comes
with the devices) that plugs into a suitable USB phone
wall charger. These sabres have heft and certainly looked
the part!
I didn’t see the extended polycarbonate translucent
‘blade’ part, as the client had already removed those for
easier transport. In my opinion, that is the hardest part
about replicating a lightsabre. Most just don’t look right.
The typical frosted plastic ‘blades’ are not convincing, and some of the toy versions I have seen even have
an extendable blade system (like an old transistor radio
aerial) that is supposed to mimic the blade ‘growing’ out
of the handle. They are usually inherently weak and next
to useless.
My customer reported that his son, who owned these
sabres, also practises kung fu. Kung fu features all manner
of blade work; it’s basically an umbrella term for any Chinese martial art. It seems the son and his friend had staged
some full-contact combat using these toys, and suddenly,
both had stopped working. Yikes!
I guess somewhere in the Chinese instructions, they
advise against hitting anything at all with them, but the
very solid construction likely gave the guys a false sense
of security as to how far they could push their swordplay. I know the feeling; after 25 years of Aikido, I was
pretty tough on my timber training swords, requiring me
to replace them every few years because splinters can
really hurt!
siliconchip.com.au
Because the acrylic ‘blade’ parts had been removed,
it was a lot easier to work with them on the bench. My
bench looks like a grenade has gone off anyway, so not
having to deal with anything but the handle part of it
was a relief.
Getting them apart
Small grub screws held everything in, and it was clear
that someone had had these apart before. Several of the
screws had their threads stripped in the aluminium housing, so they just spun and wouldn’t come out. One had been
cranked in so tightly that it had distorted the speaker casing.
It’s never good to get things in for repair that someone
has already had a go at. Never mind, there was nothing
that couldn’t be undone, so far anyway.
The button and charging port on the handle had a couple of domed Allen screws holding it into the handle. I
guessed there would be a PCB in there that held all the
electronic components. I took out the grub screws holding the speaker and those holding the LED lens assembly
completely, and when the button screws were removed, I
could slide the whole caboodle out of the case.
I was impressed with the build quality of everything
I saw – someone had put some real effort into designing
this ‘toy’.
Once I had all the gubbins clear of the case, I could also
appreciate how much they’d managed to cram into it. It
all came out as one ‘string’ of components, with the LED
assembly at the top end, then the PCB, then the battery and
finally the speaker. Everything was inter-wired and taped
together. It was very well made.
My first port of call was the battery. I know some of
these rechargeable 18650 cells can be a little shonky in
Chinese gear, so it was out with the multimeter to see what
was going on with it. Sure enough, it was flat, reading just
under 1V – very low. The customer said they might have
been sitting around a while, so I broke out my bench power
supply to give it a nudge.
As soon as I connected the ad-hoc charging cable I’d made
up for it, I was rewarded with a bright green light from the
LED, which I guessed was a charging indicator light. That was a good sign. After
a few hours of pumping 5V at 250mA
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August 2024 93
into it, I pressed the button and was rewarded
with a screeching sound from the speaker and
a bright light from the other end.
I suspect that sound is the sampled sound
of a lightsabre firing up. As you can tell, I don’t
watch many Star Wars movies!
Pressing the button sequentially changed
the LED colour and a few of the sounds.
I think that when the acrylic ‘blade’ was
attached, this would look quite cool with all
the different colours and levels. The LEDs used
dimming effects, going brighter and darker to
simulate starting up and shutting down; that’s
quite clever, and when you include the sounds,
the experience is quite immersive.
I have to say, while these LEDs were not
lasers, they were exceptionally bright. I
couldn’t look directly at them – a mistake I
made just once. I don’t know whether they
had some tricky circuitry on the board to
boost the battery’s output, but overall, the
single 1800mAh cell did a pretty good job
of making this thing shine.
So, the battery was flat on light sabre number one.
Hopefully, number two would be just as simple.
A tougher nut to crack
While I charged number one’s battery, I disassembled
number two. This was the one with a distorted speaker
housing and a few stripped grub screws. I plugged my second power supply into the charging port (using crocodile
clips as my charging lead was already in use) and initially
got... nothing. Hmm.
The battery measured less than 0.3V and was likely too
far gone even to be chargeable now. The critical level is
usually around 2V. I unplugged it – the batteries on these
devices are connected using those typical little white twopin connectors we often see, usually called JST connectors.
This makes it easy to swap things over.
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I sat number one alongside number two and plugged
the battery from one into two but still nothing happened.
Obviously, there was something else going on with number two.
I placed number one’s battery into its chain and set it
aside to let it continue charging – hopefully, that one would
return to its normal capacity with a little love. I ‘zapped’
the battery in number two just to see if I could resurrect it.
I also ordered a new one in case I needed it.
However, despite my best efforts, I could not get much
life from this battery. I could bring it up to voltage, but I
just couldn’t get any capacity out of it. Swapping things
around the other way, battery two in handle one, it would
fire up, but it would be flat in a minute.
The number two sabre itself still didn’t work. It
lit up with a flickering green charging light with
the power supply at a very specific voltage,
but it just wouldn’t do anything otherwise;
pressing the button had no effect. I tried
bridging the switch connections on the PCB,
in case the actual switch had failed, but to
no avail. Hmm...
I went over it under the microscope, looking for cracks in the printed circuit board or
other physical damage, but I could see none.
It is a wafer-thin multi-layer board; I guess
they don’t want to waste any more material than they absolutely have to. Given the
complexity of the board, there could be any
number of problems with it.
The PCB is packed with SMDs and all
the part codes had been ground off the chips,
which is so typical of this type of product.
siliconchip.com.au
I couldn’t see anything inside that might be affected by
impact damage. There were no apparent cracks, components fallen off or wires disconnected. It just didn’t work.
I suppose that, given time, I could have swapped PCBs
and other ancillary components between the two, even at a
board level, but I had to accept that number two was dead.
I did swap speakers to check that the bent one still
worked. Once I confirmed it was working, I used a pair of
vice-grips (suitably taped up to avoid leaving any marks)
to gently squeeze the speaker back into a rounder shape. It
seemed a moot thing to do, given that the sabre itself didn’t
work, but it needed doing, so I did it.
Fix or do not fix, there is no try
Sadly, with no circuits, no information online or even
any idea what the ICs were, there was not much I could
do except make sure the first one’s battery was up to spec
(which it seemed to be) and to chat with the client about
charging them up.
The charging lead came with the sabres, and it is designed
to be used with a phone charger. The problem is, as I’m
sure you can all see, is that there are several flavours of
phone chargers. The one the customer was using was a little weenie, but he did have one that stated 2A output, so I
advised him to use that one.
The smaller one may have eventually charged the batteries, given time, but when it comes to playing with swords,
especially ones that make noise and flash when you hit
them, there is no time like right now!
I reassembled the electronics into the handles, once
again marvelling at the attention to detail. For example,
the speaker had an O-ring, which sat in a groove around
the circumference and not only isolated it acoustically but
likely physically as well.
I doubt it was for water-proofing – civilian-level light
sabres do not work under water – so it must be there to
provide some damping from whatever vibrations or shock
might befall it during use.
So, mixed results then. One is up and running; the likely
problem was that the charger being used wasn’t supplying
enough juice to keep the battery charged. However, with
the second one, my guess is that it’s an internally cracked
board. Some of it seemed to work (for example, the battery charging circuitry), but something prevented the rest
from powering up.
Sadly, that was about as far as I could go without exceeding the cost of simply buying another one. Nobody wants
to pay hundreds to fix a $50 device. Still, at least he still
has one very cool, working lightsabre!
Servicing Stories Wanted
Do you have any good servicing stories that you would like
to share in The Serviceman column in SILICON CHIP? If so,
why not send those stories in to us? It doesn’t matter what
the story is about as long as it’s in some way related to the
electronics or electrical industries, to computers or even to
cars and similar.
We pay for all contributions published but please note that
your material must be original. Send your contribution by
email to: editor<at>siliconchip.com.au
Please be sure to include your full name and address details.
However, it has been playing up for the last year or two.
After switching it on, it would work normally, but after
a few minutes, the light would dim or go out. Switching
it off and on would sometimes result in it ‘resetting’ and
working fine for a bit longer, only for it to go out again
shortly after.
This intermittent fault had long puzzled me because
my initial diagnosis of it being an overheating component was not supported by the fact that it would sometimes immediately reset once power cycled. A hot component does not immediately cool down when the power
is switched off.
In any case, after putting it off for way too long, I decided
to take a look and pulled it apart, still mounted to the
bench but rotated by 180°. It is a 90 LED unit with three
curved boards of 30 surface-mount LEDs, each surrounding the magnifier lens, mounted on a removable plastic
sub-frame. The three LED boards are connected in series
by hard wire jumpers.
My initial assumption was that the fault was in the LED
driver board. Without the benefit of the magnifier (I later
realised I could’ve just popped the lens out and held it!), I
checked for obviously faulty joints, but everything seemed
in order. Noting carefully which end of the board was at
mains potential and which was low voltage, I gingerly felt
the back of the board for hot spots.
I didn’t feel any, but I must have bridged two wires that
shouldn’t have been bridged because the lights went out
and refused to come on again! I thought I had really ‘blown’
Jaycar QM3546 LED magnifier repair
I hate to throw something away that could be fixed, so I
often give it a go, whether it is mechanical or electrical. I
am an electronic repairer wannabe with a very mixed hit
rate. Needless to say, my favourite column in Silicon Chip
is Serviceman’s Log.
My Jaycar QM3546 desk-mounting LED magnifier has
been a great investment as birthdays flit by and vision
becomes more challenging. It was an essential item in my
fiddliest repair ever – my mother’s old pot plant moisture
meter in which the hairspring had come off. That required
the pointiest of soldering irons, the steadiest of hands and
the magnifiest of magnifiers.
siliconchip.com.au
An internal view of the Jaycar QM3546 LED magnifier. The
fault seemed to be temperature-related.
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August 2024 95
it this time. But after leaving it and coming back later, the
lights came on, bright at first, then dim.
After unscrewing the PCB, I noted that the one large
100V 100μF electrolytic capacitor was not bulged or leaking. I considered desoldering a leg to test its capacitance
and ESR, but first, I looked online to see if I could buy a
replacement if it was a dud. Dishearteningly, I couldn’t
find an exact replacement.
It was time to remove it from the desk to do some proper
checks. After crawling under the desk to remove the clamp
and give a contortionist a run for their money, I discovered that I need not have, as the lamp simply lifts out of
its clamped socket. Dang.
On a spare table, and with the LED sub-board flipped over
so as not to blind me, I switched it on and it came on dim.
I measured the output voltage at around 47V. I assumed
that the voltage must be higher for it to work correctly.
As a better test for overheating components, I added
a spray nozzle to a can of butane, ensured no ignition
sources were nearby, inverted the can, and sprayed the
board. The board got cold, but nothing changed; the lights
remained dim.
Getting the lights to shine brightly so I could measure the
output voltage in that condition was problematic and took
some time and fiddling. When they finally did, I quickly
measured the output voltage, expecting it to be much higher
than before – it was the same! If there was no difference
in the output voltage as the brightness changed, the fault
must be with the LED boards.
After switching the lights off and reinstalling the PCB, I
flipped the LED sub-frame over and examined them. One
LED had brown stains at each end, but after testing it, I found
it wasn’t blown and seemed to work normally. I checked
it while wearing a pair of welding goggles!
I started noticing that the more I handled the sub-frame,
the more the lights flickered. I checked and wiggled the
main power input wires, but they seemed securely fastened.
Each LED sub-board was held in place with three screws,
and I removed them now.
Since the jumpers were not flexible multi-strand wires, I
felt sure that lifting the light boards out of their little cradle
would result in breakage, and I would inevitably end up
re-soldering something. As I began to raise them, one joint
broke almost immediately. Reseating them in the cradle and
using a screwdriver to re-make the connection resulted in
the lights shining brightly.
I screwed the boards back down to prevent relative
movement and re-soldered this joint. I deeply suspected
that this was the fault all along and not merely the outcome of my disassembly. That was confirmed when the
lights came on immediately and powerfully, in contrast
to before, when the lights would take time to ramp up and
were not fully bright.
In the accompanying photo (on page 95), the screwdriver points to the initially faulty connection.
After beginning to reassemble it and almost forgetting to
include the diffuser/lens-holder, I got it all back together
and working nicely above my desk.
There were many times I toyed with the idea of discarding this lamp and buying one of the sexy new ones with
interchangeable lenses, but I knew that this one would
continue to haunt me if I didn’t at least try to fix it, a fix
that turned out to be relatively simple. It’s always about
giving it a go, taking it slowly, trying to think as logically as possible, eliminating what it isn’t, leading you
to what it is.
T. M., Capel, WA
Lucci Breeze model 213128 fan repair
A friend rang and asked me if I could come over and
look at her oscillating fan, which was making beeping
noises when switched on. The fan was bolted to the wall
and could be operated by an infrared remote control. She
was correct; when I switched on the power, the fan made
beeping noises but did nothing else. So I unbolted it and
took it back to examine it on the bench.
The fan was relatively easy to get apart, and I was soon
looking at a circuit board with a capacitive power supply
that had a 1μF X2 capacitor in series with the mains. The
capacitor drops most of the mains voltage and dissipates
little to no power because the current and voltage are out
of phase.
Above: the main PCB for the Lucci Breeze fan (shown
adjacent) with the 1μF capacitor removed. Keen eyed
readers might be able to see that the PCB silkscreen labels
that capacitor as 0.1μF.
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Silicon Chip
Australia's electronics magazine
siliconchip.com.au
This type of circuit is dangerous to work on, as the whole
electronics board is at mains potential. So I plugged it into
my mains isolating transformer to be on the safe side.
It no longer beeped when I turned it on, so I thought it
could be an intermittent fault. I measured +5V across a
large filter capacitor, so all seemed OK. But when I tried
to operate the fan, the +5V dropped to +3V.
I have seen this fault many times before where the X2
capacitor has dropped in value, so the reactance becomes
too high for the circuit to work properly. I removed the
capacitor and found it to be only 170nF instead of the
specified 1μF (1000nF). A typical tolerance of such a part
is 20%, so it was way out of spec.
I had a replacement class-X2 capacitor in my range of
spares, but it was physically a bit larger and would not fit
under the circuit board where the original was. I had to
make flying leads and attach the capacitor to the plastic
case around the circuit board, ensuring the system was
still well insulated.
The fan worked as intended when powered on, with the
remote controlling the speed and oscillation. After reassembling it, I returned the fan and reattached it to the wall. My
friend was very happy to have her cooling fan going again,
as summer was just around the corner.
Editor’s note: we often find that replacement X2 capacitors are physically larger than the failed ones. We wonder why!
J. W., Hillarys, WA
Extension lead repair
I was sorting through some items in a box given to me
years ago that I hadn’t gotten around to checking when I
found a short extension lead. I noticed that the cord-grip
nut was missing from both the plug and the socket, so I
would have to repair it before I could put it with our other
extension leads.
I started at the plug end and immediately noticed that
the plug was on the wrong end of the cable because the
Active and Neutral wires crossed over instead of going
straight to their respective terminals. That meant I would
have to remove the plug and the socket and swap them.
I turned my attention to the socket end and could see
that the Active and Neutral wires did not cross over but
were connected to each other’s terminals! I don’t know
who made this extension lead, but they obviously did not
know what they were doing.
With both the plug and the socket removed, I fitted them
to the correct ends of the cable, along with cord-grip nuts,
ensuring that the Active and Neutral wires connected to
their correct terminals. I then tested the lead with my multimeter, and all was good. Whenever I encounter an extension lead that is not ours, I always check it to verify that
it’s in good condition and wired correctly.
This particular lead could have been dangerous in certain
circumstances, for example, if some idiot used the ‘black
is Earth’ idea (a common vehicle terminology, which isn’t
correct either).
I remember reading a Serviceman’s entry in Electronics
Australia decades ago, where a similar situation existed
with a live PA system. If you don’t know what you are
doing with mains wiring, it’s best to leave it to someone
who does.
B. P., Dundathu, Qld
SC
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