Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems.

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Esmail Bonakdarian
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?

Hello,

I have a 27-inch Toshiba tv (Model 27A41 -
http://www.cs.oberlin.edu/~esmail/tv.jpg) that is only 4 years old and
already failing.

I was hoping someone could give me an idea what the problem might be,
and if it's worth even bothering hauling this behemoth to be fixed. Or
alternatively, how long this tv might last in its current state.

I get different bands of colors "bowing in" from the sides, where I
seem to be loosing one of the RGB channels. There are no magnetic
sources etc nearby. Here is a pic of what the tv looks like when it
displays a blue only menus screen for my vcr.

http://www.cs.oberlin.edu/~esmail/tv_problem.jpg

In addition to the color problem, I sometimes also get some flicker
accompanied by some crackling sound as if a contact is being
connected/disconnected. Every once in a while (very rare) the tv flips
back to being normal for a few seconds, but generally the messed up
colors are permanent. The flickering/buzzing sound happens somewhat
rarely too but not as rare as getting a normal pic.

Here are two video clips showing the tv in action:

http://www.cs.oberlin.edu/~esmail/tv_problem.avi
http://www.cs.oberlin.edu/~esmail/tv_problem2.avi

Any ideas?

Thanks,
Esmail
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Tech Data
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?


Esmail Bonakdarian wrote:
Hello,

I have a 27-inch Toshiba tv (Model 27A41 -
http://www.cs.oberlin.edu/~esmail/tv.jpg) that is only 4 years old and
already failing.

I was hoping someone could give me an idea what the problem might be,
and if it's worth even bothering hauling this behemoth to be fixed. Or
alternatively, how long this tv might last in its current state.

I get different bands of colors "bowing in" from the sides, where I
seem to be loosing one of the RGB channels. There are no magnetic
sources etc nearby. Here is a pic of what the tv looks like when it
displays a blue only menus screen for my vcr.

http://www.cs.oberlin.edu/~esmail/tv_problem.jpg

In addition to the color problem, I sometimes also get some flicker
accompanied by some crackling sound as if a contact is being
connected/disconnected. Every once in a while (very rare) the tv flips
back to being normal for a few seconds, but generally the messed up
colors are permanent. The flickering/buzzing sound happens somewhat
rarely too but not as rare as getting a normal pic.

Here are two video clips showing the tv in action:

http://www.cs.oberlin.edu/~esmail/tv_problem.avi
http://www.cs.oberlin.edu/~esmail/tv_problem2.avi

Any ideas?

Thanks,
Esmail


The problem you're showing wouldn't be that expensive to reapair by an
honest, qualified tech. If it ended up being what I think it is, I
wouldn't charge more than 40 bucks to take care of it. Call around.
Don't toss it just because you don't know what's wrong with it.

www.techdata-kicksass.net

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Esmail Bonakdarian
 
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Default Can you take a look? (help diagnose problem on TV ...) toss orrepair?



The problem you're showing wouldn't be that expensive to reapair by an
honest, qualified tech. If it ended up being what I think it is, I
wouldn't charge more than 40 bucks to take care of it. Call around.
Don't toss it just because you don't know what's wrong with it.


Hi,

tossing stuff is really something I'd rather not do. Can you give
me an idea of what you think is wrong with it? That way I can at
least mention this when I call around. I'd gladly pay that amount
to have it fixed.

The closest authorized place is about half an hour down the interstate
(I live in a tiny town w/ no local repair place), and said it might
take them 3 or 4 weeks to get to it. I only have one tv so that seems
long.

Should I take it to best buy?

Thanks,
Esmail
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ian field
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?


"Esmail Bonakdarian" wrote in message
news:KSWgg.4497$Id2.1713@trnddc03...


The problem you're showing wouldn't be that expensive to reapair by an
honest, qualified tech. If it ended up being what I think it is, I
wouldn't charge more than 40 bucks to take care of it. Call around.
Don't toss it just because you don't know what's wrong with it.


Hi,

tossing stuff is really something I'd rather not do. Can you give
me an idea of what you think is wrong with it? That way I can at
least mention this when I call around. I'd gladly pay that amount
to have it fixed.

The closest authorized place is about half an hour down the interstate
(I live in a tiny town w/ no local repair place), and said it might
take them 3 or 4 weeks to get to it. I only have one tv so that seems
long.

Should I take it to best buy?

Thanks,
Esmail


The fault is either convergence or colour purity, the CRT has a "shadow
mask" behind the phosphor coated glass face plate the R, G, & B electron
beams have to be accurately aimed at the tiny holes in the shadow mask so
they only strike the correct colour phosphor dot (or stripe).

There are two possibilities: the first is the degauss posistor in or near
the mains input circuitry, this demagnetises the shadowmask each time the
set is switched on, a faulty posistor can give weird colour distortions but
is usually more random in appearance than the division into R, G & B shown
in your photo.

More likely is the static convergence and purity rings on the CRT neck
between the scan coils and the CRT base board, these rings are usually
moulded plastic with a magnetic filler and are usually mounted on a
ring-lock assembly which can (in rare cases) work loose and allow the rings
to move. The back most spigots on the assembly are the ring-lock cam, if
this is not loose then either the rings have been previously tampered with
and re tightened or the assembly has been subjected to a strong external
magnetic field, if the rings are loose they may have moved so realignment
shouldn't be too difficult.

If you can get hold of a service manual and borrow a test pattern generator
the realignment procedure is really quite straightforward matter of
following the steps described in the manual..


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Clint Sharp
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?

In message , ian field
writes
The fault is either convergence or colour purity,

It's not convergence.
More likely is the static convergence and purity rings on the CRT neck
between the scan coils and the CRT base board, these rings are usually
moulded plastic with a magnetic filler and are usually mounted on a

The fault is almost definitely not related to the purity/convergence
rings as it's intermittent/changing, the crackling noise gives it away
as a problem with the degauss circuit, either a dry joint on one leg of
the posistor or coil connector, a faulty posistor or degauss coil. I'd
replace the posistor first and re-solder all associated connections.

If you can get hold of a service manual and borrow a test pattern generator
the realignment procedure is really quite straightforward matter of
following the steps described in the manual..

If you mess about with the rings to try and fix a fault, you'll
definitely need a test pattern generator and a lot of patience.



--
Clint Sharp


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Esmail Bonakdarian
 
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Default Can you take a look? (help diagnose problem on TV ...) toss orrepair?

Hi Ian,

ian field wrote:

If you can get hold of a service manual and borrow a test pattern generator
the realignment procedure is really quite straightforward matter of
following the steps described in the manual..


Well, that's out of my comfort zone/area of expertise, but if I am
understanding you correctly, you concur with the previous poster in
that this seems like a fairly trivial repair and shouldn't cost too
much?

Once again, I would rather not have to toss this thing out if a fairly
simple (and cheap) repair can take care of it.

Thanks,
Esmail
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ian field
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?


"Clint Sharp" wrote in message
...
In message , ian field
writes
The fault is either convergence or colour purity,

It's not convergence.
More likely is the static convergence and purity rings on the CRT neck
between the scan coils and the CRT base board, these rings are usually
moulded plastic with a magnetic filler and are usually mounted on a

The fault is almost definitely not related to the purity/convergence
rings as it's intermittent/changing, the crackling noise gives it away as
a problem with the degauss circuit, either a dry joint on one leg of the
posistor or coil connector, a faulty posistor or degauss coil. I'd replace
the posistor first and re-solder all associated connections.

If you can get hold of a service manual and borrow a test pattern
generator
the realignment procedure is really quite straightforward matter of
following the steps described in the manual..

If you mess about with the rings to try and fix a fault, you'll definitely
need a test pattern generator and a lot of patience.



--
Clint Sharp


That's certainly possible, and dry joints around the degauss posistor (or
its relay if it has one) are not at all unlikely now so many manufacturers
are using lead-free solder - it seems to almost fall apart after only a
couple of years!!!


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Andy Cuffe
 
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Default Can you take a look? (help diagnose problem on TV ...) toss or repair?

On Mon, 05 Jun 2006 14:47:40 GMT, "ian field"


There are two possibilities: the first is the degauss posistor in or near
the mains input circuitry, this demagnetises the shadowmask each time the
set is switched on, a faulty posistor can give weird colour distortions but
is usually more random in appearance than the division into R, G & B shown
in your photo.

More likely is the static convergence and purity rings on the CRT neck
between the scan coils and the CRT base board, these rings are usually
moulded plastic with a magnetic filler and are usually mounted on a
ring-lock assembly which can (in rare cases) work loose and allow the rings
to move. The back most spigots on the assembly are the ring-lock cam, if
this is not loose then either the rings have been previously tampered with
and re tightened or the assembly has been subjected to a strong external
magnetic field, if the rings are loose they may have moved so realignment
shouldn't be too difficult.



I vote for #1. It can't be the purity adjustment because he said it
"flips" back to normal sometimes. Purity rings don't adjust
themselves. A bad connection in the degaussing circuit could return
to normal occasionally.
Andy Cuffe


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Esmail Bonakdarian
 
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Default Can you take a look? (help diagnose problem on TV ...) toss orrepair?

Hi,

So the consensus is that this is a fairly trivial
thing to repair with a bill well under $100 ?

I realize it's hard to diagnose something based on
a video & jpg posted on the web, but if everyone's
guess is right.

So, it's best to go for the repair, if I'm drawing
the right conclusions on the above posts, yes?

Esmail
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