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Science Forum Index » Electronics - Repair Forum » Toshiba TV success!
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| Author |
Message |
| Forrest |
 Posted: Sat May 03, 2008 4:55 pm |
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Guest
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I posted about my 32 inch Toshiba TV with the squatty bodied, cone headed
picture with the three inch black band across the bottom. Thanks to the
excellent advice that I received here, I sent away for a dozen or so, high
temp caps for the vertical section and the surrounding area of the board.
I'm a rookie and was mostly worried about getting zapped. That didn't happen
and I was able to unsolder the caps using Rat Shack wick. It worked pretty
good but was rather tedious. In fact I only used about half the caps that I
ordered. I started to resolder the IC, but thought better of it when the
solder started to run down each connection and wanted to ooze together. I
guess one is supposed to totally remove all of the old solder and then redo
it. I also almost messed up a trace by trying to bend the leg of a cap
straight before cutting it off. In retrospect, I see how stupid that was. It
didn't break but did lift off of the board slightly. The trace was at the
edge of a part of the circuit and I could have duplicated the path to the
next component by soldering a small wire between them. I was wondering if I
should have tacked it down with a drop of Super Glue or maybe a small dab of
hot melt. Anywhooooo .... plugged it all back up and hit the switch and,
bada bing ... works like a charm! I put the cover back on and gave it a good
bouncing and shaking to make sure nothing was ready to come loose. I then
left it on for over 24 hours ... still fine. The worst part of the whole
thing is a sore back from lugging it our to the garage and back.
While doing some reading on caps, one maker's page said, "do not
straighten caps, that are soldered into place." Am I the only person here
that can't seem to resist? It's like not squeezing a black head.
The only other minor problem that I ran into was, a small cap without any
kind of polarity marking and nothing on the board. I reinstalled that one.
How common are those?
Well, needless to say, I'm glad that I didn't just toss the TV in the trash.
I wasn't about to lug that monster down to some shop, owner unknown, and pay
to have it fixed. It's a 1994 model ... not something that one wants to sink
a lot of money into. Hard to believe that just a few dollars in caps made it
right as rain. Thanks again, for all of the help. |
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| Arfa Daily |
| Posted: Sat May 03, 2008 8:14 pm |
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Guest
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"Forrest" <REMOVETHISrunforrest1@hotmail.com> wrote in message
news:Ib5Tj.13031$GE1.12514@nlpi061.nbdc.sbc.com...
Quote: I posted about my 32 inch Toshiba TV with the squatty bodied, cone headed
picture with the three inch black band across the bottom. Thanks to the
excellent advice that I received here, I sent away for a dozen or so, high
temp caps for the vertical section and the surrounding area of the board.
I'm a rookie and was mostly worried about getting zapped. That didn't
happen and I was able to unsolder the caps using Rat Shack wick. It worked
pretty good but was rather tedious. In fact I only used about half the caps
that I ordered. I started to resolder the IC, but thought better of it when
the solder started to run down each connection and wanted to ooze together.
I guess one is supposed to totally remove all of the old solder and then
redo it. I also almost messed up a trace by trying to bend the leg of a cap
straight before cutting it off. In retrospect, I see how stupid that was.
It didn't break but did lift off of the board slightly. The trace was at
the edge of a part of the circuit and I could have duplicated the path to
the next component by soldering a small wire between them. I was wondering
if I should have tacked it down with a drop of Super Glue or maybe a small
dab of hot melt. Anywhooooo .... plugged it all back up and hit the switch
and, bada bing ... works like a charm! I put the cover back on and gave it
a good bouncing and shaking to make sure nothing was ready to come loose. I
then left it on for over 24 hours ... still fine. The worst part of the
whole thing is a sore back from lugging it our to the garage and back.
While doing some reading on caps, one maker's page said, "do not
straighten caps, that are soldered into place." Am I the only person here
that can't seem to resist? It's like not squeezing a black head.
The only other minor problem that I ran into was, a small cap without any
kind of polarity marking and nothing on the board. I reinstalled that one.
How common are those?
Well, needless to say, I'm glad that I didn't just toss the TV in the
trash. I wasn't about to lug that monster down to some shop, owner
unknown, and pay to have it fixed. It's a 1994 model ... not something
that one wants to sink a lot of money into. Hard to believe that just a
few dollars in caps made it right as rain. Thanks again, for all of
the help.
Glad you got a result, and we were all able to help you along the way. There
is no real 'trick' to neat soldering, just lots of practice, and the right
tools. For soldering IC pins and general joints of the sorts of sizes and
density that you will see on the average TV board, you need an iron of
between about 25 and 40 watts, with either a pencil tip, or a chisel tip, no
more than about 2mm across the flat. The solder doesn't want to be much more
than 0.7mm diameter for most general work. When reworking joints such as
those on the chip that you started on, lay the tip's flat, or side of the
pencil point tip, against the side of the existing joint, until it melts
nicely. Then, with the iron still aginst the pin, feed in a tiny amount of
new solder to the opposite side of the joint. Just enough to make the joint
look clean and shiny again (we're not talking lead-free joints here, of
course ...!) and not so much that the joint 'floods' and starts to run. The
solder should stay completely confined to the joint. If it tries to bridge
the gap to the next pin, then you've got too much on there, and you need to
wick off and start again.
I must admit that if I see a cap in the area that I'm working in that isn't
straight, I do have a pedantic tendency to apply the iron to its legs, and
make it back into a proper upright little soldier ...
There are all sorts of caps of lower values that have no polarity. As a rule
of thumb, all electrolytics have polarity. There is one exception to this,
and that is the bipolar electrolytic. You do come across them being used as
coupling caps, particularly in audio gear, but even then they are fairly
rare compared to the very common polarised type.
Arfa |
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| dBc... |
| Posted: Wed May 14, 2008 11:59 pm |
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Guest
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Arfa..
With the spelling as "polarised type" you may also be in the U.K or
Australia...
Perhaps they're not all that common over there, here in the U.S. they
show up in a variety of consumer and non-consumer products. Further,
as illustrated by Mouser, they're not that specialized. No doubt that
they aren't used as much as aluminum polarized electrolytic
capacitors, but they show up in a variety of various electronics these
days. If they didn't, the good folks at Mouser would have absolutely
no reason to carry the variety of assortments they currently stock.
Which further implies that there is a demand for them.
Cheers,
Mr. Mentor
"Arfa Daily" <arfa.daily at (no spam) ntlworld.com> wrote in message
news:MkyWj.3989$Nq2.1292 at (no spam) newsfe29.ams2...
|
| "dBc" <not_necessary at (no spam) thanks.com> wrote in message
| news:RmvWj.100$oJ4.3499473 at (no spam) petpeeve.ziplink.net...
| > Greetings Arfa & others..
| >
| > Regarding:
| > " There are all sorts of caps of lower values that have no
polarity.
| > As a rule
| > | of thumb, all electrolytics have polarity. There is one
exception to
| > this,
| > | and that is the bipolar electrolytic. You do come across them
being
| > used as
| > | coupling caps, particularly in audio gear, but even then they
are
| > fairly
| > | rare compared to the very common polarised type."
| >
| >
| > Not all that uncommon or rare. I've even got them in my AT&T fixed
| > line telephone.
| >
| > Reference:
| >
http://www.mouser.com/search/Refine.aspx?Ne=2203862+1447464&N=2203862+1323038&Ns=P_SField
| >
| > Especially note under, Product:
| > Bi-Polar/Non-Polar Electrolytic Capacitors
| >
| > Pick a value and click on the Apply Filters button. Take a look at
any
| > of your major electronics component distributors, they'll have a
| > variety of them.
| >
| > Cheers,
| > Mr. Mentor
|
| I don't dispute that they exist in suppliers' catalogues, nor that
they are
| used occasionally in a variety of kit, but I think that anyone in
the repair
| business would agree with me that they are "fairly rare" in day to
day
| encounters with most consumer equipment of average quality and
design. I
| thought that was what I was conveying by using that phrase. Perhaps
I should
| have said "comparitively rare". To qualify that, I have in stock
perhaps 500
| polarised electrolytic caps of maybe 30 different values. I use them
on a
| daily basis. Compare this to 5 each of two different values of
bipolar
| electrolytic. The last time I used one was probably 3 months ago in
a
| Musical Fidelity preamp (very expensive, and in my opinion not very
well
| designed).
|
| If you took 20 'average' service engineers, and asked them what a
bipolar
| electrolytic was, I'm willing to bet that probably seven or eight of
them
| would never even have heard of them, and fifteen or more would never
have
| replaced one, or had any in stock.
|
| As for them being in a telephone, that is a bit of a special case,
with lots
| of high level AC voice signals, floating on high DC levels. With
signals
| like this flying around inside, any coupling cap that needs to be
big enough
| to have to be an electrolytic, will of course need to be bipolar ...
|
| Arfa
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