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TIP: When replacing capacitors in a video monitor...

  • Thread starter Matt J. McCullar
  • Start date
M

Matt J. McCullar

Jan 1, 1970
0
Something I learned the hard way...

I was replacing a bunch of electrolytic capacitors in a video monitor. I
removed the originals all at once, taking careful notes about each location,
its reference designation, and the value and voltage of each capacitor. All
the original caps went into a zip-lock bag.

Then I got a fresh batch of new capacitors, tested each one first, and
installed them in one go. I carefully checked off each capacitor on my list
as I went. (Another tip: I colorize the top of each new electrolytic
capacitor with a red magic marker so I can readily see if I've missed
something later.)

This was about 30 capacitors. It's very easy to put one in backwards, as
you well know. I was very, very careful.

I apply power, and...

BOOM! One cap literally got blown completely out of the monitor! It sailed
past my ear and landed about three feet away! It was a small one, a 10 uF,
50 volt job, but it learned how to fly that day.

Well, poop. I quickly removed power and found the location of the fried
capacitor. I checked my notes again. Something in my gut told me to
re-double-check. I went back through the bag of original capacitors and
checked off each cap's value and voltage rating.

Now, here's the golden moment: I found my mistake. I had the right value
of capacitance, and I'd installed it correctly. My mistake was the voltage
rating. I had installed a 50-volt capacitor, which is what the original
capacitor was rated for. But... The original capacitor had some white
rubbery gunk on it; that had been applied on the circuit board at the
factory to keep parts and wiring from moving around much. It's basically a
rubberized version of hot glue. This white gunk had hardened all over one
side of this cap, and it had masked something critical: one digit. That's
all, just one digit. I removed the gunk.

The original capacitor was rated for 250 volts, not 50! No wonder the
replacement cap exploded. :)

So, keep this in mind the next time you're replacing a bunch of capacitors
or other electronic parts: make sure you can read ALL the numbers and
letters on them!!!

Matt J. McCullar
 
J

Jerry G.

Jan 1, 1970
0
I don't know your service experience, but you gave a simple example of
why professional service people warn people who don't have the proper
training and experience to give their service work out to qualified
services to have their repairs done.

I know of cases where people have had injury from a terrible electric
shock, of cases where people had fires, and who were injured from
exploding parts that have not been correctly replaced.

But... For some reason many people think they can do the work
themselves, thinking that they will save a few dollars.


Jerry G.
======
 
I don't know your service experience, but you gave a simple example of
why professional service people warn people who don't have the proper
training and experience to give their service work out to qualified
services to have their repairs done.

I know of cases where people have had injury from a terrible electric
shock, of cases where people had fires, and who were injured from
exploding parts that have not been correctly replaced.

But... For some reason many people think they can do the work
themselves, thinking that they will save a few dollars.

Jerry G.
======













- Show quoted text -

Thats exactly why it is of the utmost importance to wear safety
googles and other protective gear when attemping such a dangerous
task. I usually drink first.
Rick
 
S

Smitty Two

Jan 1, 1970
0
Jerry G. said:
I don't know your service experience, but you gave a simple example of
why professional service people warn people who don't have the proper
training and experience to give their service work out to qualified
services to have their repairs done.

I know of cases where people have had injury from a terrible electric
shock, of cases where people had fires, and who were injured from
exploding parts that have not been correctly replaced.

But... For some reason many people think they can do the work
themselves, thinking that they will save a few dollars.


Jerry G.
======

Professionals - in any profession - are injured and killed, too. Let the
service tech who hasn't had an electrolytic capacitor explode, please
stand up... being an amateur is no reason to leave things alone.
 
Gotta side with the amateurs on this one. I am by no means a tech. I
have made mistakes while repairing things. You fix the mistake and
move on. If you wanted a safe hobby, you would have taken up golf.
Nothing safer than little white projectiles flying all over a field
with drunk guys yelling fore. I think anyone whos been in this hobby
for more than a year has probably had a decent shock before. Lord
knows I have. But it doesn't affect me any. But it doesn't affect
me any. The trick is to know when I a project is above your head and
send it off if you cant handle it. If you don't think the hobby is
dangerous, I know of someone who was moving a large game and if fell
striking him on the head. He later developed neurological problems
that was diagnosed as Lou Gerhigs disease. That is if I overheard
everything correctly. Just about everything about these games can
cause death. Whether its electrocution, fire, or being crushed by an
HS-5 dynamo. But we do it cause we love it. And we try to better our
skills by gradually taking on smaller projects until we are ready for
larger ones. If you get right down to it, no tech was born a tech.
They learned it somewhere whether its MIT, ITT or the TSHK(the school
of hard knocks.) Just my 2cents.
 
G

gamefixer

Jan 1, 1970
0
I don't know your service experience, but you gave a simple example of
why professional service people warn people who don't have the proper
training and experience to give their service work out to qualified
services to have their repairs done.

I know of cases where people have had injury from a terrible electric
shock, of cases where people had fires, and who were injured from
exploding parts that have not been correctly replaced.

But... For some reason many people think they can do the work
themselves, thinking that they will save a few dollars.

Jerry G.
======













- Show quoted text -

Nah, practice makes perfect. Your going to have to try REALLY hard to
kill your self with a monitor. FWIW, Matt's a veteran in this group
and in the field. We all make mistakes...

Matt (a different one)
 
D

Dave Plowman (News)

Jan 1, 1970
0
The original capacitor was rated for 250 volts, not 50! No wonder the
replacement cap exploded. :)
So, keep this in mind the next time you're replacing a bunch of
capacitors or other electronic parts: make sure you can read ALL the
numbers and letters on them!!!

There's usually a big difference in size between a 50 and 250 working
voltage one. And if replacing the lot it should have been obvious by the
size difference between all the new ones?
 
C

carneyke

Jan 1, 1970
0
Something I learned the hard way...

I was replacing a bunch of electrolytic capacitors in a video monitor. I
removed the originals all at once, taking careful notes about each location,
its reference designation, and the value and voltage of each capacitor. All
the original caps went into a zip-lock bag.

Then I got a fresh batch of new capacitors, tested each one first, and
installed them in one go. I carefully checked off each capacitor on my list
as I went. (Another tip: I colorize the top of each new electrolytic
capacitor with a red magic marker so I can readily see if I've missed
something later.)

This was about 30 capacitors. It's very easy to put one in backwards, as
you well know. I was very, very careful.

I apply power, and...

BOOM! One cap literally got blown completely out of the monitor! It sailed
past my ear and landed about three feet away! It was a small one, a 10 uF,
50 volt job, but it learned how to fly that day.

Well, poop. I quickly removed power and found the location of the fried
capacitor. I checked my notes again. Something in my gut told me to
re-double-check. I went back through the bag of original capacitors and
checked off each cap's value and voltage rating.

Now, here's the golden moment: I found my mistake. I had the right value
of capacitance, and I'd installed it correctly. My mistake was the voltage
rating. I had installed a 50-volt capacitor, which is what the original
capacitor was rated for. But... The original capacitor had some white
rubbery gunk on it; that had been applied on the circuit board at the
factory to keep parts and wiring from moving around much. It's basically a
rubberized version of hot glue. This white gunk had hardened all over one
side of this cap, and it had masked something critical: one digit. That's
all, just one digit. I removed the gunk.

The original capacitor was rated for 250 volts, not 50! No wonder the
replacement cap exploded. :)

So, keep this in mind the next time you're replacing a bunch of capacitors
or other electronic parts: make sure you can read ALL the numbers and
letters on them!!!

Matt J. McCullar

I always change a part or two and did the next part. Sometimes test
the unit after changing one or two parts, checking for problems caused
by new part. I don't like pulling too many parts without checking
work performed, it depends on job.
 
W

wc3p

Jan 1, 1970
0
Something I learned the hard way...

I was replacing a bunch of electrolytic capacitors in a video monitor. I
removed the originals all at once, taking careful notes about each location,
its reference designation, and the value and voltage of each capacitor. All
the original caps went into a zip-lock bag.

Then I got a fresh batch of new capacitors, tested each one first, and
installed them in one go. I carefully checked off each capacitor on my list
as I went. (Another tip: I colorize the top of each new electrolytic
capacitor with a red magic marker so I can readily see if I've missed
something later.)

This was about 30 capacitors. It's very easy to put one in backwards, as
you well know. I was very, very careful.

I apply power, and...

BOOM! One cap literally got blown completely out of the monitor! It sailed
past my ear and landed about three feet away! It was a small one, a 10 uF,
50 volt job, but it learned how to fly that day.

Well, poop. I quickly removed power and found the location of the fried
capacitor. I checked my notes again. Something in my gut told me to
re-double-check. I went back through the bag of original capacitors and
checked off each cap's value and voltage rating.

Now, here's the golden moment: I found my mistake. I had the right value
of capacitance, and I'd installed it correctly. My mistake was the voltage
rating. I had installed a 50-volt capacitor, which is what the original
capacitor was rated for. But... The original capacitor had some white
rubbery gunk on it; that had been applied on the circuit board at the
factory to keep parts and wiring from moving around much. It's basically a
rubberized version of hot glue. This white gunk had hardened all over one
side of this cap, and it had masked something critical: one digit. That's
all, just one digit. I removed the gunk.

The original capacitor was rated for 250 volts, not 50! No wonder the
replacement cap exploded. :)

So, keep this in mind the next time you're replacing a bunch of capacitors
or other electronic parts: make sure you can read ALL the numbers and
letters on them!!!

Matt J. McCullar

Thanks for sharing the story, Matt!

I won't tell you to spend gobs of money paying someone else to make
the mistakes for you, since they're only human too. It is a wise man
(person) who listens to someone's story and logs the wisdom in their
own skull , then hears the little voice repeating that story in their
ear at the right time.

Bob WC3P
 
J

Jeff

Jan 1, 1970
0
Thats exactly why it is of the utmost importance to wear safety
googles and other protective gear when attemping such a dangerous
task. I usually drink first.
Rick

Heavily and without prejudice.
 
J

Jay

Jan 1, 1970
0
I disagree, that example can happen to ANYONE, professionals and amateurs
alike. I wouldn't doubt it happens to professionals more often because of
pure cockiness. An amateur is more likely to take necessary precautions and
check the work over and over.

I for one, if I have the tools or equipment to do so will do anything myself
rather than have a professional do it. (not without doing a little research
first of course) Diagnosing a problem is a different story.
 
P

PeterD

Jan 1, 1970
0
Something I learned the hard way...

I was replacing a bunch of electrolytic capacitors in a video monitor. I
removed the originals all at once, taking careful notes about each location,
its reference designation, and the value and voltage of each capacitor. All
the original caps went into a zip-lock bag.

You are kidding right? And you are trying to offer advice?

First bit of advice to you: Replace ONE AT A TIME...
Second bit of advice to you: Check, then double check that yuo have
the right part, in the right way.
 
M

Matt J. McCullar

Jan 1, 1970
0
There's usually a big difference in size between a 50 and 250 working
voltage one. And if replacing the lot it should have been obvious by the
size difference between all the new ones?

Indeed it was. Fortunately, the silk screening on the circuit board is what
gave me the clue. After the fact it said that the original cap was
physically much larger than the replacement I had installed. Sometimes
newer drop-in replacment caps are smaller than the originals, but not by
THAT much!

And thanks for the backup, everybody. Everybody makes mistakes, no matter
how many years you've got under your belt. And electricity, like steam and
the ocean, does not respect an idiot; it's waiting for you to make a
mistake. You gotta have respect for it or it'll kill you.

So learn from the mistakes of others as well as your own and don't be shy
about passing on what you've learned. It just might help someone else in
the future.
 
N

N Cook

Jan 1, 1970
0
Matt J. McCullar said:
Indeed it was. Fortunately, the silk screening on the circuit board is what
gave me the clue. After the fact it said that the original cap was
physically much larger than the replacement I had installed. Sometimes
newer drop-in replacment caps are smaller than the originals, but not by
THAT much!

And thanks for the backup, everybody. Everybody makes mistakes, no matter
how many years you've got under your belt. And electricity, like steam and
the ocean, does not respect an idiot; it's waiting for you to make a
mistake. You gotta have respect for it or it'll kill you.

So learn from the mistakes of others as well as your own and don't be shy
about passing on what you've learned. It just might help someone else in
the future.

It would help if there was a standard, some mark + , some mark - and some
mark with arrows consisting of a line of negative signs leading to the other
side
 
M

Morse

Jan 1, 1970
0
Jerry G. said:
I don't know your service experience, but you gave a simple example of
why professional service people warn people who don't have the proper
training and experience to give their service work out to qualified
services to have their repairs done.

I know of cases where people have had injury from a terrible electric
shock, of cases where people had fires, and who were injured from
exploding parts that have not been correctly replaced.

But... For some reason many people think they can do the work
themselves, thinking that they will save a few dollars.


Jerry G.
======


Hmmm, here's a little story-

After several attempted and failed warranty repairs on my cooker to fix the
same fault, and all by different engineers, my son leant on the metalwork
and got a shock. I did a quick test with a multimeter from chassis to a
nearby earth point and, guess what- no earth.

I removed the small access panel on the back of the cooker where the mains
feed enters, and discovered that the internal earth leads had been
disconnected from ther terminal block and taped together. The mains lead had
also had its earth disconnected from the block and had a small length of
thin, solid core red wire taped to it which went nowhere.

One tech who came out said he'd 'done something to the wiring' to try and
eliminate the fault (the clock and oven randomly go off) so it's likely he
is responsible for this, but the worrying thing is that all the techs have
signed the paperwork saying that the appliance had been tested for safety.
The first rule of checking for electrical safety is surely checking the
earth- it took me literally 5 seconds so why did they all miss this? The
engineer who called today said it was disgraceful and he would be 'having a
quiet word' with the engineer who did it, but I had to suppress the urge to
point out that *he* was happy enough to sign it off as safe without checking
it, pots and kettles spring to mind.

So, no offence, but qualified techs can and do not only screw up but are
capable of potentially homicidal recklessness. Some individuals are
competent, some are not, regardless of qualifications. I have no formal
qualifications but I would *never* have done something like this, the
importance of a good earth on metal kitchen appliances is blatantly obvious
and cannot be overstated. Had I not have had an electronic background, the
missing earth may well have gone unnoticed and the shock may have been
dismissed as static. The consequences don't bear thinking about.

Morse
 
M

Meat Plow

Jan 1, 1970
0
Professionals - in any profession - are injured and killed, too. Let the
service tech who hasn't had an electrolytic capacitor explode, please
stand up... being an amateur is no reason to leave things alone.

I've blown them up on purpose but can't recall having one explode on the
bench.
 
K

Ken Layton

Jan 1, 1970
0
Common sense dictates that you change one capaitor at a time. You
should also verify polarity and value of the capacitor you're
replacing and the new one too. Remember that monitor manufacturers
sometimes have incorrectly marked the polarity on the chassis too
(Hantarex I'm pointing directly at you).
 
W

William

Jan 1, 1970
0
Matt J. McCullar said:
Something I learned the hard way...

I was replacing a bunch of electrolytic capacitors in a video monitor. I
removed the originals all at once, taking careful notes about each
location,
its reference designation, and the value and voltage of each capacitor.
All
the original caps went into a zip-lock bag.

Then I got a fresh batch of new capacitors, tested each one first, and
installed them in one go. I carefully checked off each capacitor on my
list
as I went. (Another tip: I colorize the top of each new electrolytic
capacitor with a red magic marker so I can readily see if I've missed
something later.)

This was about 30 capacitors. It's very easy to put one in backwards, as
you well know. I was very, very careful.

I apply power, and...

BOOM! One cap literally got blown completely out of the monitor! It
sailed
past my ear and landed about three feet away! It was a small one, a 10
uF,
50 volt job, but it learned how to fly that day.

Well, poop. I quickly removed power and found the location of the fried
capacitor. I checked my notes again. Something in my gut told me to
re-double-check. I went back through the bag of original capacitors and
checked off each cap's value and voltage rating.

Now, here's the golden moment: I found my mistake. I had the right value
of capacitance, and I'd installed it correctly. My mistake was the
voltage
rating. I had installed a 50-volt capacitor, which is what the original
capacitor was rated for. But... The original capacitor had some white
rubbery gunk on it; that had been applied on the circuit board at the
factory to keep parts and wiring from moving around much. It's basically
a
rubberized version of hot glue. This white gunk had hardened all over one
side of this cap, and it had masked something critical: one digit. That's
all, just one digit. I removed the gunk.

The original capacitor was rated for 250 volts, not 50! No wonder the
replacement cap exploded. :)

So, keep this in mind the next time you're replacing a bunch of capacitors
or other electronic parts: make sure you can read ALL the numbers and
letters on them!!!

Matt J. McCullar

I never remove ALL the caps at one time. I do it one at a time and verify
voltage and polarity of the old cap first before installing the new
one....sometimes the markings on the circuit board are wrong.
 
C

clifto

Jan 1, 1970
0
Ken said:
Common sense dictates that you change one capaitor at a time.

Anyone who's ever built a kit of any complexity can see the value of doing
all the unsoldering and cleaning at once, followed by doing all the parts
insertion and clipping at once, followed by doing all the soldering at
once.
 
J

Jay

Jan 1, 1970
0
The problem Matt ran into was misreading a value on a cap .It can be made
whether you do all the caps at once or one at a time. Matt took all the
necessary precautions needed to avert any wrong installations of the caps by
noting each caps place, value and polarity rather than rely on the circuit
markings (to me, that shows some experience there) Though it is more time
consuming and there is more chance of a mistake, I see no problem with
removing all the caps at once so long as those steps are taken.
 
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