6 Silicon chip Australia’s electronics magazine siliconchip.com.au
environment where not all equipment
will be used in air-conditioned areas.
However, to use the higher rated ca-
pacitors would have called for a larger
PCB, which would not have suited the
project’s aim. Nevertheless, I consider
this to be a major flaw in the design.
Richard Kerr
Cessnock, NSW.
Nicholas responds: we are planning
to offer an upgrade to our most re-
cent preamplifier design (March-April
2019; siliconchip.com.au/Series/333)
to provide six stereo inputs with re-
mote control and pushbutton switch-
ing. We are hoping that this will also
be able to be built as a standalone au-
dio input switcher.
The main reason for using an
OPA2134 over the NE5532 would be
its higher input impedance as it has
JFET input transistors. If that isn’t re-
quired, NE5532 or LM833 would be
my choice. They are both cheap and
excellent performers for audio (low/
noise distortion).
I also much prefer using 105°C ca-
pacitors as they have a much longer
life even at lower operating tempera-
tures. It is true that they are generally
larger than their 85°C rated equiva-
lents; however, you can purchase rel-
atively small 105°C-rated capacitors
with good MTBF figures.
You can see in the Universal Regu-
lator article (May 2015) that the ca-
pacitors used have considerable room
around them. For the 2200μF 25V ca-
pacitors, you can use diameters up
to 16mm (18mm if you’re pushing it)
which gives you hundreds of options
for using 105°C rated capacitos.
For example, you could use Nichi-
con UBT1E222MHD which is 16mm in
diameter and rated for 10,000 hours
at 125°C. And the 100μF 25V capaci-
tors can be up to 10mm in diameter
which gives you plenty of high-relia-
bility, long-life options.
By the way, electrolytic capacitors
are now available which can handle
operating temperatures up to 150°C!
Much better to repair than replace
expensive consumer goods
I read Nicholas’ comments in the
March issue, on the current state of
affairs regarding repairable consumer
goods, with a smile on my face.
I spend a fair amount of time do-
ing just that for friends, neighbours,
friends of friends etc. Many people
are reluctant to repair equipment be-
cause manufacturers can charge more
for parts and repairs than the original
item cost when purchased new. How-
ever, this becomes a major problem
when parts are no longer available...
For example, I was trying to repair a
wide-screen TV where the main CPU
was history (along with the EEPROM).
Although I could purchase and fit a
new CPU and EEPROM, the firmware
wasn’t available, and neither were the
startup operating parameters stored in
the EEPROM. So I couldn’t fix it.
I have another relevant anecdote
about my Holden Vectra; a very nice
car that was a joy to drive, powerful
yet economical. One day I was driving
home from Brisbane and it stopped. To
cut a long story short, it needed a part
which was no longer available. The
number cast into the part by Holden
didn’t appear in any manual, and the
Holden parts computer system didn’t
recognise it.
After waiting over a week for Holden
to locate this part, I eventually found
one in the UK. I bought two in case it
failed again!
How long will it be before we have
to throw away larger and theoretically
‘durable’ items due to the high repair
costs and higher parts cost? How long
before manufacturers decide to pull all
support for given a product shortly af-
ter it goes on sale? When spare parts
or firmware are no longer available,
what happens then?
Then we find components with no
identifying marks, MPUs that destroy
themselves if anyone tries to download
the code they run on and PCBs fully
encased in resin preventing access to
the boards and components on them.
I understand intellectual ‘property
rights’ and copyrights, and they do have
their place, but what about consumers
rights? What does the consumer do if
parts are no longer available and the
new software or firmware will not run
on the equipment they want repaired?
Technology is amazing and has been
integrated into our everyday lives, but
let’s not allow the manufacturers of
said equipment to control our financ-
es or the global economic markets.
We bought it, we own it and we use
it, why are we being denied the right
to have it repaired?
My PC keeps updating itself even
though updates are turned off and one
such update (for Windows 10) caused
me to lose the use of my USB ports!
As my keyboard and mouse areboth USB models, It was a struggle to
remove that update and fix the mess
it left behind.
Fixing broken products makes more
sense. Products with a decent working
lifetime make sense. And yet consum-
ers have fallen right into the “just buy
a new one” trap!
Comments: under existing Consumer
Law, manufacturers cannot withdraw
support for a new product – it must
be supported for a “reasonable” time.
Although, what that means exactly is
anyone’s guess.
Dave Sargent,
Maryborough, Qld.Extension leads for bench supplies
Sometimes I need to have power
some distance from my lab power
supply. My solution to this problem
was to make some extension leads up.
One end of the twin-core cable has
piggyback banana plugs (so I can dou-
ble-check the meter output or run a
second cable) that plugs into the ex-
isting sockets. The other end has one
of those screw terminal joiner blocks
so I can connect any wires in.
This means that I can power up a
prototype in the middle of the room,
without worrying about using battery
modules. I might need a longer one
for greater freedom of movement. This
would have the benefit of saving on
batteries during development.
Darcy Waters,
Wellington, New Zealand.
Comment: keep in mind that depend-
ing on the current draw, you could
have a significant voltage drop across
such a cable. One of our bench sup-
plies has separate sensing terminals
so it would be possible to create kelvin
probe style wires to suit it (they would
need four cores although the two sens-
ing wires could be thin).
Although it’s awkward, we gener-
ally prefer to run a mains extension
lead to the bench supply and put it
on a wheeled trolley to get it close to
the load, both for the convenience of
front panel access and to get decent
voltage regulation.Electrical safety standards not being
properly enforced
Your editorial in the April issue
made me pretty angry. I started out in
electronics pulling apart mains-pow-
ered equipment that had failed due
to bad design or poor quality com-
ponents.