common mistakes in electronics repair
TRANSCRIPT
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Common Mistakes In Electronics
RepairMany of us had been interested in electronics repair from a very young age,
but to some, the interest could have started in our 40’s or even 50’s! No
matter what’s your age, electronics repair is fun and this hobby can be turned
into profits if you know what to do with your knowledge t is very e"citing
when you discover that electronics repair is the field that is really meant for
you
#ay and night you search the web for more information about electronicsrepair and hope to be able to understand and solve electronics problems $ou
are %ust simply e"cited and love electronics repair &owever, for a beginner to
become professional level, one needs to avoid some mistakes that beginners
always make 'elow are the ( most common mistakes a beginner should
avoid
1) Not using Isolation transformers
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)n isolation transformer is a linear transformer, often with symmetrical
windings, which is used to decouple two circuits )n isolation transformer lets
an )* signal or power be taken from one device and fed into another device
without electrically connecting the two circuits solation transformers block
transmission of #* signals from one circuit to another, allowing )* signals to
pass solation transformers also block interference caused by ground loops
n electronics troubleshooting, an isolation transformer has a ratio of ++
which is used as a safety precaution -to eliminate the shock ha.ard for hot
chassis device such as /M/1 2hat means 340 )* in and 340 )* out $ou
may also use the configuration such as two 340+3 transformers connectedin the below manner
340+3 -2+1 and +3 back to 340-231
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ithout the isolation transformer, e"posed live metal in a device under test is
at a ha.ardous voltage level relative to grounded ob%ects such as an
oscilloscope ground lead 2hat means that if you connect the oscilloscope
ground to the primary side of the switch mode power supply -/M/1, it willcause the building to trip! ith the transformer, as there is no conductive
connection between transformer secondary and earth -ground1,there is no
danger of touching a live part of the circuit while another part of the body is
earthed -grounded1
f you are new in this field, do yourself a favour and get an isolation
transformer 6emember, the power transformer must be rated to handle the
power of any e7uipment connected to it
2) Turning on the equipment and taking measurements
f you are very sure of what you are doing then you can proceed with this kind
of test f you are new and without guidance, you may feel uncomfortable or
have no confidence to turn on the set and perform the voltage or signal test
using either your multimeter or oscilloscope $ou could blow up the power ic
and other components while checking the supply voltage by shorting the **
-#* supply pin1 with the ad%acent pin
had personally heard a %unior tech -many years ago when was working1
shout, 8 want to 7uit this %ob9, simply because he had accidentally blown up a
monitor power section 2hat incident really scared him due to the loud bang
generated by his own carelessness while performing a voltage measurement
when the power was on :ind someone that has this kind of e"perience to
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show you the right way of doing it, otherwise you may create more problems
than you want
3) Onl using one multimeter
f you want to be a successful electronics troubleshooter, then don’t rely only
on one single digital or analogue multimeter 2he more meters you have, the
faster you can detect a fault 2here is no way with %ust one multimeter you can
accurately test all the electronic components found in a circuit board t had
already been proven that different components need different types of meters
to check them :or electrolytic capacitors, you need an ;/6 meter to test it,
for a
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!) "ot #riting do#n our solution
henever you have solved a problem, you need to write it down >ur brains
%ust can’t remember every problem that we have solved /imply by referring to
our notes, with a snap of your fingers, you could solve a complicated problem
within minutes or even seconds! &ere is a tip for you on how to write down
those important notes
f you have solved a 8no power9 symptom in a /M/, don’t %ust write 8no
power in model )+3?4 and the solution is to replace the power ic and an
electrolytic capacitor9 2his kind of note won’t really help you much when you
refer back to it $ou need to write something like 8:rom the @*?A43 power
ic datasheet, pin ( should have about +3 to +B #* but found only few volts
6eplacement of the ic did not cure the problem and the supply voltage to the ic
was still low /o began to check the components related to the supply voltageline and found one electrolytic capacitor -*3C4(uf 50 #*1 had high
;/6 6eplacement of the two components cured the fault9
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Now don’t stop there *ontinue with your notes by drawing a simple power ic
schematic and show where the bad capacitor was connected as shown in the
above photo
$) %oor soldering
f you are weak in your soldering skills, then suggest that you put in more
time to practice it 2his is to avoid a solder bridge that could cause more
harm to the board have seen solder bridges a number of times when
customers told me that the set had been repaired by someone before guess
the repairer could have been %ust starting out, because after removing the
solder bridge and replacing a few components, the set came back to life again
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/imply practice on %unk circuit boards and make yourself good at soldering so
that you will not add more problems to the board you are troubleshooting
&) Improperl installed components
Many times have seen circuit boards that have improperly installed
components 2he technician could actually have solve the problem, but
because of their own negligence, the e7uipment was unable to be
repaired $ou will understand what mean from the photos below
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$ou must be very careful when removing components, making sure they are
put back in the correct location after they had been checked and found to be
good 2here is a possibility a manufacturer could have labelled a component
wrong, however, this rarely happens /o, in order to prevent this kind of
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mistake, before soldering out any component, make sure you look at the
markings on the board first
(1 "ot asking questions
)sking 7uestions is not a sin thus you should not keep them to
yourself 'eginners usually have a lot of things playing in their minds like
8how to check this9, 8how to test that9, 8why did this component blow9,9 what
is the replacement part9, etc $ou should try to find your answer first before
asking the 7uestion as this will force you to think f you still cannot find the
answer, there are several resources where you can get your 7uestions
answered $ou could post your 7uestion into an online forum, call up your
electronics buddies or course mates, ask your lecturer or your mentor,
etc Many times, asking 7uestions and getting answers will save you hours offrustration
Conclusion D n fact the above article is not only meant for beginners, it is
meant for seasoned repairers too :ind out where your weaknesses are and
learn how to improve them so that your %ourney to becoming a professional
repairer can be cut short The most important thing is our mindset )
wrong or bad mindset could cause you to be la.y, have no ob%ective and
negative thinking /et your path right by having the right mindset and you will
see success very 7uickly