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SERVICEMAN’S LOG
I got the power
Dave Thompson
The other day, something relatively unusual happened around here, which
revealed a flaw in our system. For the first time in a very long time, we
experienced a power cut. It wasn’t just one of those ‘oh, the power has gone
off and has come back on in minutes’ cuts – it was off for many hours.
I assumed some contractor somewhere had dug a little
too deeply, or perhaps in the wrong place, and had put
the bucket through the cable to our part of town. I fully
expected things to come back online pretty quickly. After
15 minutes, I leaned across the fence to my neighbours and
asked if they’d also lost power, just in case it was something in our household that had given way.
Fortunately, they’d lost power too. Oh wait, that came
out wrong; I mean that it wasn’t a fault specific to me that
I would have to get someone to fix. Perhaps it was one of
those substation explosions you hear about. I could imagine the control room at the power station, with a map of
the city and bits of it going dark in sequence as the system
fails. Sadly, I think that’s just movie mayhem.
Either way, something had obviously happened to our
supply and we could do nothing but ride it out and wait.
This obviously left us dead in the water regarding our
computers, my workshop, our local area network internet connectivity – pretty well everything. Fortunately, we
have mobile phones, so we could at least maintain some
kind of connectivity.
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After 30 minutes, I bit the bullet and called our power
supplier. I soon discovered that I was gazillionth in the
queue for fault reporting and support, so I wasn’t going to
waste much time on that. It was obviously being reported
already; my whinging about it wouldn’t make much difference in the bigger picture.
I also didn’t want to burn up the remaining charge in my
phone battery, even though since the quakes here, I have
maintained several different USB battery packs so we can
charge phones. I was really caught short when the quakes
hit in 2011 and we lost power for a week. Back then, my
phone had only 24% charge to begin with. With no way
of charging it, it soon went flat.
The bad old days
Not that it was much good in the early days anyway,
because all the cell towers lost mains power and the backup
batteries only lasted two hours. Plus, they were so overloaded that the whole system crashed. If we were lucky,
the odd text might go through, but voice calls were mostly
impossible.
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October 2024 89
Items Covered This Month
• Unlit ruminations
• Workzone MIG (metal inert gas) welder repair
• Bando Technic 5D transceiver repair
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
Of course, nothing worked once the towers’ backup batteries went flat. Landlines had been severed, and while
some users in some suburbs had communications, the rest
of us did not.
I vowed never to be caught out again. I have at least a
week’s worth of battery power here now for charging phones
or any other tech. As a bonus, and again, as a result of the
quakes, we have gas heating and cooking, so at least we
could make a cup of tea while we watch the house fall
apart in the aftershocks.
However, our newest gas fire, installed recently, requires
electric power to run. Given that this recent power cut
happened in the middle of winter, my concern was that
we’d soon get very cold. We also have several heat pumps
around the house to provide basic warmth in the winter
and cooling in the summer but, of course, they were offline
as well due to the outage.
Yes, I know this is a very first-world problem and that
many people, including those in so-called first-world countries, experience power loss regularly for various reasons.
However, it brought back a lot of bad memories for me, to
those times when we and others had no power for weeks on
end, in the darkest days of our post-quakes, semi-dystopian
society where, let’s not forget, almost 300 people died.
No traffic lights, no streetlights, no mobile phones, no
landlines. It was a strange time. The problem was that the
earth under everything in many parts of the city turned to
a liquid-like quicksand (a phenomenon known as liquefaction). All the pipes and conduits and anything else under the
tarmac on the roads just floated to the surface of the street.
The earthquake’s strength was such that it just lifted the
asphalt, circuit junctions and access covers and ruined the
roads. That’s aside from breaking all the pipes, cables and
whatever else was nestled inside those conduits.
This, of course, plunged entire suburbs into darkness.
Luckily – if there was a lucky side to it – it was February
and summer, so we didn’t really have to worry about heating. But, with all the sewers broken, there were no toilets,
no water, no power, no phone lines. We were cut off.
I realise that many other countries had things worse. At
around the same time, Haiti experienced a huge quake,
which killed thousands, as did Japan, with wider-reaching
consequences.
Not having power back then was a real problem. Everything in our home relied on power. My serviceman’s mind
sprung into action and, as soon as the shops were open, I
vowed to buy a generator. In the meantime, I had an old
gas cooker and an old gas heater that used the ubiquitous
9kg bottle of LPG.
One company was giving away gas (many companies did
this in an effort to help, whether it was free milk, bread
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Silicon Chip
or gas), and I took my old bottle down to have it filled. Of
course, it was out of date, so they wouldn’t touch it, let
alone fill it. I bought two new ones from a nearby big box
store and had them filled for free.
I did have to queue for hours at each place, as milk, bread,
petrol and gas were being strictly rationed. It really was
an eye-opener as to how people behaved under duress. At
least our stove and (if we needed it) heating would work.
Anyway, back to our recent power outage. As I mentioned, power outages are rare here. The last one we had
was seven years ago, when we moved into this place. We’d
had the power off as we renovated the house, and when we
put it back on, it suddenly failed. Thinking it was something we’d done, I did as much troubleshooting as possible.
I could tell power was coming in from the wires, but it
died at the old ceramic pole fuse mounted on the house’s
bargeboards. I had to call the power company, and the guy
climbed the ladder and touched the wire and it simply fell
off. Easy job, I thought. But no, new pole fuses actually
have to go on poles. But the pole on our back section was
apparently an old pole (60 years) and not high enough.
So, the pole had to be replaced and the new fuse put on
top of it. Red tape holds the nation together, or so they say.
It was a completely ridiculous chain of events. Anyway,
that’s the last time the power went out, so it’s a rare occurrence, which is why I thought some contractor must have
dug up the cable or a substation had failed somewhere.
Time for the generator to shine
Whatever the cause, our house was dark and dead in the
water in the middle of winter. After three, I decided it was
time to dig out the generator I had queued to buy 13 years
ago, and fire it up. If the power was not going to be back
on for hours, we’d need to get something sorted.
I knew we had hours before the freezers started thawing,
but I wanted to hedge my bets. Even with the generator, we’d
have to be pretty careful what we plugged in; it isn’t one
of those huge Detroit diesel powered ones I worked
on at the airline back in the day.
Two of those could power a city!
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This one might do some phone chargers, the fridge/
freezer and maybe the TV, at a stretch.
The first challenge was getting the thing out
of storage in my garage. You’d think a ‘prepper’
like me would have it set up and ready to go in a
purpose-built enclosure next to the house, but no.
And it is such an awkward thing to move.
It isn’t overly heavy, but it is a two-person lift because
there’s nowhere one person can pick it up and carry it from.
It has a frame around it, but no finger or hand holds. You
also cannot get a sack-barrow underneath it because it
seems like something would get bent or damaged if I
tried. So, it needs two people.
I could drag it from under all the rubbish I’d piled
on it to the garage door, but from there to the house
is quite a way, so I had to involve my wife. That,
of course, is a whole other column.
We managed to get it onto the porch, where
we could run it out of the weather and add a
cable through a cracked window to power what
we needed.
The next challenge was firing it up. In the interest of being prepared, I have started it periodically
over the years, ensuring I had enough petrol in it
and even a spare can next to it should the you-knowwhat hit the fan again. The problem is, of course, that petrol loses its punch over time and this lot had been in there
for a while now.
I didn’t want to just tip it out, but as the tank in the generator seems to have allowed what was in there to evaporate,
even with the fuel tap off and the cap tightly applied, I had
to refill it with the can I had. With the tank full, it should be
good for about seven hours if my calculations are correct.
Mind you, I failed maths so many times at school I can’t
even count!
All joking aside, I was hoping this thing would start. It
has a 7HP (5.2kW) motor and electronic ignition, according to the label, so I was expecting it to fire up easily. It
didn’t. In the usual design stupidity that many machines
seem to have these days, the pull cord has to be pulled at
a weird angle off-centre from the pull starter, adding drag
on the line and making it harder to start.
Whoever designed these things must have been part of
the company Bastards Inc. from that TV show, “The Fall
and Rise of Reginald Perrin”. Saltshakers with no holes
in them, gloves with just three fingers. Surely they’d look
at it and think, how can we make this work better? But it
appears not.
I pulled on the cord a dozen times but nothing happened.
With lots of blue language and gnashing of teeth, I realised
I hadn’t turned the fuel tap on. I know, I know. It’s the little
things that get to you. Anyway, once I opened that, with a
few pulls on the cord, it sputtered into life.
Boy, these things are loud! It was now sitting right outside the window, and I was rueing the fact I hadn’t built a
soundproofed box for it elsewhere and ran some cabling. We
might have power now, but the price to pay was the noise.
A comedy of errors
I still had to connect it up, which meant breaking out the
extension cords. Fortunately, I know how to roll these up
properly, given my years on the road in the music business.
Unfortunately, the last time I used the longest of my
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cables, which of course was the one I needed now, I was lazy
and just gathered it up and chucked it on the garage floor.
Now it was a rat’s nest, caught in everything possible on
the concrete. Great, there’s 30 minutes of my life I’ll never
get back. Note to self: roll the cables properly next time!
I plugged everything in and fired the generator again, this
time hitting the ‘power on’ button, a standard-looking panel
switch like you see on lots of equipment, similar to those
on the rear of a computer power supply. This should liven
up the two mains sockets provided. However, I got nothing. No power output. Hrmm, I must be doing something
wrong. It’s not unusual (Tom Jones Syndrome).
I haven’t used this generator other than to test it in the
past, and I might need to (shock, horror) read the instruction manual. Though quite where that manual is, I don’t
know. I could always hit the internet to find it. Oh, wait...
The control panel has two olde-worlde moving coil
meters that showed I should have 230V available from the
mains socket and 12V DC from the red and black banana
sockets beneath them. So the generator itself appeared to
be generating. I broke out my multimeter and tested both;
I got no reading from either socket.
Great; I’m glad this wasn’t a dire emergency because I
was really behind the eight ball here. There must be another
switch or something I was overlooking. I just couldn’t
see one on the fascia, so I had to go down on my hands
and knees, in the noise and smoke, to try to see what was
going on.
Finally, I found a circuit breaker, stuck around the back,
on the motor assembly. I threw caution to the wind and
pressed it, and was rewarded with beeps and lights through
the open window. The governor on the genny kicked in
too, so it sensed there was some load on it.
Why they didn’t put that breaker on the front panel is
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October 2024 91
another one of the design ‘features’ that people who never
have to use these things come up with. At least I know it
is there now.
So we sat down and thought: what was most important? My wife works remotely and so getting our computers and internet up and running was most pressing. The
fridge and freezer would stay cold for a while at least, so
we decided to prioritise getting our network up and the
internet back online.
That wasn’t much load for the generator; it was revving
like mad right outside our office window. On reflection,
that was not the wisest place to put it.
Just as I was reconfiguring the plugs to get everything
up and running, the office light came on. I’d switched it
on so I’d know when the power came back. Excellent! All
that mucking around for nothing. At least I’d wrung out
the generator and had shown up some flaws in my systems.
Next time, hopefully I won’t be caught as short!
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Silicon Chip
Editor’s note: I wrote an article in the January 2020
issue titled “What to do before the lights go out” about
preparing for blackouts and emergencies. Since then, I
have purchased another inverter, a generator, extension
cords, power meters, jerry cans, propane cylinders and
numerous battery-powered lights and torches. While I
haven’t needed them much yet, as Dave implies, it pays
to be prepared.
Always put fuel stabiliser in the petrol you’re keeping
for emergencies. After a year, pour it into your car’s tank
and refill the can with fresh petrol (not E10; it’s hygroscopic and corrosive). If testing a generator, switch the fuel
supply off and let it die so you don’t have old fuel sitting
around in it for years.
Workzone Inverter MIG Welder repair
Several years ago, I purchased a Workzone gasless MIG
welder from ALDI Special Buys. I’ve done a lot of work
with this welder, which was reliable until recently.
I was building a bike rack for our bikes and all was going
well until I got to a particular section. The welder started running erratically, making it difficult to make a decent weld. It
was a hot day, so I thought it might be overheating. However,
the welder worked well again when I turned the job over.
I went on to the next section of the project. It was fine as
I was welding one end, but it would not weld at all when
I went to the other end. I went back to the initial end, and
it worked fine there, but once again, when I went to the
other end, it did not weld.
Then it stopped welding completely. I no longer thought
it was overheating as the overheat light was not on and the
welder felt cool. I hadn’t done much continuous welding
on this job; had I pushed the welder much harder on other
jobs, so it should have been all right.
Returning from lunch, I found that the welder still did
not work. It did nothing when I pressed the trigger, even
though the welder was obviously running, as I could hear
the fan and the power light was on.
I started troubleshooting it by dismantling the handpiece.
This is easy to do as there is a nut on each end. I got my
multimeter and tested the microswitch and found it was
working. So it was time to take the lid off and look further.
The front panel is held on with three screws, one on
top and two underneath. Another seven screws hold the
cover on. With the cover removed, I found where the thin
cable from the microswitch connects to the control board
behind the front panel.
I pulled the plug out, connected my multimeter to it
(on continuity mode) and pressed the trigger again. Nothing happened, indicating a break in the cable between the
handpiece and the welder. I then shorted the two pins on
the control board and the wire feed motor ran. I laid that
wire on the ground clamp, shorted the pins again, and the
welder sprang to life.
To replace the cable, I had to remove the clamp that
holds the outer welding cable to the welder and disconnect the ground cable from the circuit board. I removed the
screws from one end of the board and loosened the screws
at the other end so I could raise the board to access the nut
underneath it.
I found some heavier twin-flex, soldered it to the end
of the original cable and pulled it through the outer cable.
I reconnected both ends by splicing and soldering, then
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applied heat-shrink tubing insulation. I reassembled the
welder and got back to the job at hand.
B. P., Dundathu, Qld
Bando Technic 5D repair
I may also suffer from Dave Thompson’s “Serviceman’s
Curse”. Sometimes repair jobs take far more time than was
bargained for or is reasonable.
I recently bought a non-working HF amateur band transceiver, as it looked worthy of restoration. It’s a brand I had
never heard of, Bando from South Korea, dating to the late
1980s. I found the service manual, all in Korean, but fortunately, the schematics were all readable.
As with most transceivers of that era, valves produce
the output, in this case, two 6146Bs driven by a 12BY7.
The remainder is all solid state. As the final valves operate with an 800V plate supply, any service work must be
done carefully.
This high voltage is derived from an iron core transformer
via a bridge rectifier and filtered by two series 47µF/450V
capacitors with 470kW balancing resistors. On inspection,
one capacitor was a dead short, which put the entire 800V
on the other, which had obviously blown! I decided to
concentrate on the receiver side first. After removing the
capacitors, I temporarily disconnected and insulated the
high-voltage winding from the transformer to the rectifier.
Some cosmetic problems needed to be fixed first. A
power connector on the back panel was missing, and an
ugly heavy power cable passed through the rectangular
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hole with a home-made cable clamp. In addition, a large
toggle switch had been added, which I found was used to
turn off the filament supply to the 6146s. In addition, the
wires to the microphone gain control were damaged.
I removed the switch and associated wiring and drilled
out the hole to take a proper cable clamp with a new power
cable. I covered the rectangular hole with a small plate. The
top and bottom covers needed a good clean-up; a repaint
may be a good idea at some stage. A couple of knobs were
not original, but a friend reckons he could make some to
match using a 3D printer.
Now I could safely turn it on to check the receiver operation. The display came up, and the tuning knob changed
the frequency correctly on all bands. Connecting a signal
generator, some bands appeared to work, but several were
completely deaf. The band switch is of the wafer type;
using contact cleaner, I managed to get all bands working
except for the 28-30MHz ones.
A 1µV input signal gave an excellent SNR on all but the
top band in that range, which needed at least 20dB more.
I ordered some replacement high-voltage electrolytics, but
being impatient, I robbed three 350V capacitors from discarded computer power supplies and made up a capacitor
that could handle 1050V, together with 270kW balancing
resistors. That enabled me to get the transmitter working.
I connected a 50W 100W dummy load to the antenna
terminal and switched to Tune on the 7MHz band. Immediate success; I had a power output that I could peak with
the two variable capacitors of the pi-coupler. There is also
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October 2024 93
a Drive control that tunes the plate circuit of the 12BY7,
but it did absolutely nothing!
The circuit diagram shows a section of a three-gang variable capacitor. The other two sections are used for peaking
the receiver’s tuned circuits on either side of a low-noise
dual-gate Mosfet preamplifier (Q1). The drive control operates the variable capacitor via a couple of plastic gears.
On close inspection, the gears were moving, but the one
attached to the capacitor shaft via a friction fit was not rotating the shaft. For some reason, it was jammed completely.
It was purely fortuitous that it was stuck in a position that
had the receiver working reasonably well. But to achieve
maximum output power, it did have to operate.
I tried all sorts of ways to move it, such as sliding the
gear off and trying to rotate it with pliers, all to no avail.
How about removing the capacitor and sorting out its
problem? About three hours later, having used all my
solder-removing tools, including a hot air pencil, I had to
admit defeat. There are many connections to the capacitor on the circuit board, and even though it is single-sided,
it was tightly connected, mainly via the solid end plates.
Any further attempts could have damaged the PCB, so
I had to develop a Plan B. Looking at the circuit diagram,
there is a 10nF capacitor (C60) from the plate of the 12BY7
to the variable capacitor. How about disconnecting it and
adding an external capacitor? I had several suitable variable capacitors accumulated over the decades that I had
fortunately never thrown away.
Doing a quick lash-up of the connections, it looked workable, and sure enough, I could peak the drive voltage to the
6146 valves. I made a bracket from 1.6mm aluminium and
bolted it to the top of the original variable capacitor which,
by luck, had 2.5mm tapped holes on top.
Adding a knob was a workaround solution but not a satisfactory one. It meant that the top of the transceiver had
to be left off, exposing what turned out to be 170V peak-topeak at RF on the stator. That could cause a nasty RF burn!
But how could I connect to the original drive shaft? One
suggestion was to make up a 3D-printed gear to mesh with
the one already there, but it just would not fit. Another
alternative would be a couple of pulleys and a belt drive,
which also looked impractical. Then, I came up with the
idea of using two universal couplings. Looking at where
they would fit and the angle between the shafts, it seemed
a likely solution.
Off to AliExpress, and not surprisingly, there are heaps
of them from different suppliers for different shaft diameters. The ones in the transceiver are 6mm in diameter, so
I ordered a couple for a grand total of $14. They arrived
within two weeks, just after I also received a length of
6mm-diameter tubing.
As you can see from the photo, it all came together quite
easily. The only gotcha was having to carefully drill out one
end of the 6mm coupling to 6.35mm (1/4in), as that was
the shaft diameter of the 100pF variable capacitor. Tuning
with the front knob is now quite smooth and the drive can
be peaked accurately.
Remember the two extra gangs on the capacitor? The
receiver sensitivity and noise figure were quite good on
all but the top band, so I decided just to peak the slugs
on the coils slightly on either side of the middle of each
usable band. For example, on the 40m band, I peaked L9
at 7.1MHz and L16 at 7.2MHz. That applied
to all the other bands.
I now have a workable transceiver with a
clean 100W SSB output on all but the 10m
band. After many hours of work, I decided to
leave that for another day. Once the proper
high-voltage electrolytics arrive, I will
replace the temporary arrangement. Yes, it
took a long time, but the satisfaction of getting it to work more than made up for it.
SC
C. K., Mooroolbark, Vic.
Above: the Korean-made Bando transceiver
and a close-up of its RF section.
Left: the universal coupling (with the
connectors unplugged).
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