Hi, I have a Sharp 25K-S100 and the color convergence at the corners is not
good at all. The upper-left corner is especially bad and after leaving the
TV on for more than about 10 minutes, a small purple color patch develops
in that area. Any idea how I can repair this? I know in the FAQ it
mentions adjusting the ring magnets and the yolk, but I'm not 100% sure how
I would begin doing this, if this will even work, and can I perform this
with the television on to see if everything will work ok? Please help me,
thanks.

Tony

Tony wrote in :

Hi, I have a Sharp 25K-S100 and the color convergence at the corners
is not good at all. The upper-left corner is especially bad and after
leaving the TV on for more than about 10 minutes, a small purple color
patch develops in that area. Any idea how I can repair this? I know
in the FAQ it mentions adjusting the ring magnets and the yolk, but
I'm not 100% sure how I would begin doing this, if this will even
work, and can I perform this with the television on to see if
everything will work ok? Please help me, thanks.

Tony


BTW... here's a picture of it in it's messed up state:

http://web.njit.edu/~amp8/files/shar****ue.jpg

On 27-Dec-2004, Tony wrote:

Hi, I have a Sharp 25K-S100 and the color convergence at the corners
is not good at all. The upper-left corner is especially bad and after
leaving the TV on for more than about 10 minutes, a small purple color
patch develops in that area. Any idea how I can repair this? I know
in the FAQ it mentions adjusting the ring magnets and the yolk, but
I'm not 100% sure how I would begin doing this, if this will even
work, and can I perform this with the television on to see if
everything will work ok? Please help me, thanks.

It halps if you have a manual or specific information on
converging Sharp sets. You have to converge with the set on
else you can't see what's happening. Most ring magnets are
stuck together with paint and it's a pain in the butt to separate
them without breaking them. It's quite easy to electrocute yourself
whilst watching the picture in a mirror, and not watching where
your hands are going. I use teletext to see convergence as it's
impossible to converge on a normal picture. Mark the position
of the rings before you start so you can get back to where they were.
Make sure the degauss circuit is working before you start, it
may be the only thing that is wrong. It may not be possible to
converge the set if it has had the flyback replaced with a
generic. Some sets need stick on magnets to sort out
problems at the screen corners. Removing metal screens,
if there are any, can upset convergence, so the history of
repairs may provide a clue as to why the convergence is off.
To do the job properly you need a convergence pattern
generator, a DVD player on pause, with text such as
the distribution rights on the screen, or teletext is a poor
substitute. If a generic flyback has been used the EHT may
be out of spec, and if the scan amplitudes have been adjusted
to compensate for the different sensitivity due to the
changed EHT, you've got problems, which is why the sets
history is useful, like when did the problem appear, just after
a repair?

The reason why the purity and convergence is going out when the set warms
up, is because there is something changing specifications as the set heats
up. This looks to be something with the CRT, rather than the electronics. It
is possible that the mask in the tube is warping inside as it gets warmed
up, and thus changing specs. The warpage only needs to be a few thousandths
of an inch to show an error of some type.

The ring magnets on the neck of the tube that are located in back of the
yoke will adjust the centre convergence, or the overall. The inner most
magnets are for doing the purity set-up, and the outer two groups are for
the R,G and then the B,R. These are very critical to adjust and take a lot
of practice. The purity set-up will interact a little with the convergence
magnets when moved. You would have to acquire the feel for this. I would
strongly suggest using a grating generator when doing this type of set-up.

As for the corner adjustments, they are using edge or strip magnets. These
are sort of longish looking devices that are made of a flexible plastic that
is not thermo sensitive. At the end of the plastic strip is a small magnet.
On the opposite end there is some two-way adhesive to make it stick to the
wall of the tube. This magnet is inserted down between the yoke and tube
bell at the base of the neck and manipulated to perform the corner and side
convergence. Also the purity can be effected, and there can be some
compromise to get things right.

In anycase, doing the convergence set-up is difficult if you are not set-up
for this, and do not have the necessary experience behind you.

In the case of your set, when reading your description, you may be chasing
your butt when doing the convergence. The reason is that there are some
defects with the set, rather than it being purely a convergence problem. If
you have a thermo sensitive shadowmask in the CRT, and you are trying to set
up the purity and convergence, this is not going to be practical. There may
be some increased drift as the CRT starts to deteriate some more, which it
most likely will. When CRT's age, they can become unstable in a number of
ways, including that their emission will decrease over usage time.

I would be considering to replace the set, rather than to put time and
effort in to it. When you start messing with the convergence take the
attitude, that you will most likely be soon scraping the set.

One thing that is very important is to take care for safety issues when
working in these sets. When you are doing the convergence set-up, you will
be working very close to some seriously high voltages, that have enough
current source behind them to cause severe burns, and or injury. These
adjustments must be done with the set running, and properly warmed up.

In the learning stage, the technical people doing this type of work are
working under close supervision. An experienced tech usually will not work
alone when doing this type of work. There is always the opening for an
accident. It is part of the job. I have been doing this type of work for
more than 30 years. I have had a few good zaps from sets. A number of times
over the years that I worked in the service centres, I've seen someone badly
hurt, who thought that they knew what they were doing.

--


Greetings,

Romeo E. Albert
============

"Tony" wrote in message
...
Hi, I have a Sharp 25K-S100 and the color convergence at the corners is
not
good at all. The upper-left corner is especially bad and after leaving
the
TV on for more than about 10 minutes, a small purple color patch develops
in that area. Any idea how I can repair this? I know in the FAQ it
mentions adjusting the ring magnets and the yolk, but I'm not 100% sure
how
I would begin doing this, if this will even work, and can I perform this
with the television on to see if everything will work ok? Please help me,
thanks.

Tony

wrote in :


On 27-Dec-2004, Tony wrote:

Hi, I have a Sharp 25K-S100 and the color convergence at the
corners is not good at all. The upper-left corner is especially
bad and after leaving the TV on for more than about 10 minutes, a
small purple color patch develops in that area. Any idea how I can
repair this? I know in the FAQ it mentions adjusting the ring
magnets and the yolk, but I'm not 100% sure how I would begin doing
this, if this will even work, and can I perform this with the
television on to see if everything will work ok? Please help me,
thanks.

It halps if you have a manual or specific information on
converging Sharp sets. You have to converge with the set on
else you can't see what's happening. Most ring magnets are
stuck together with paint and it's a pain in the butt to separate
them without breaking them. It's quite easy to electrocute yourself
whilst watching the picture in a mirror, and not watching where
your hands are going. I use teletext to see convergence as it's
impossible to converge on a normal picture. Mark the position
of the rings before you start so you can get back to where they were.
Make sure the degauss circuit is working before you start, it
may be the only thing that is wrong. It may not be possible to
converge the set if it has had the flyback replaced with a
generic. Some sets need stick on magnets to sort out
problems at the screen corners. Removing metal screens,
if there are any, can upset convergence, so the history of
repairs may provide a clue as to why the convergence is off.
To do the job properly you need a convergence pattern
generator, a DVD player on pause, with text such as
the distribution rights on the screen, or teletext is a poor
substitute. If a generic flyback has been used the EHT may
be out of spec, and if the scan amplitudes have been adjusted
to compensate for the different sensitivity due to the
changed EHT, you've got problems, which is why the sets
history is useful, like when did the problem appear, just after
a repair?


It's actually been a minor problem for a while, the TV has never been in
for repairs and at the cost it'd probably be to have them do it, it'd be
more economical to buy a brand new set. But since this is going to be
for my dorm room, it was basically my grandparents' old TV set. At this
point should I just open it up and look for anything in particular that
could be wrong, maybe one of the ring magnets is out of place or
something along those lines? Or even this yolk that people talk about?
And what's the danger area to touch, the copper coil things only or is
there more? Thanks for all your help!

"Jerry G." wrote in
:

The reason why the purity and convergence is going out when the set
warms up, is because there is something changing specifications as the
set heats up. This looks to be something with the CRT, rather than the
electronics. It is possible that the mask in the tube is warping
inside as it gets warmed up, and thus changing specs. The warpage only
needs to be a few thousandths of an inch to show an error of some
type.

The ring magnets on the neck of the tube that are located in back of
the yoke will adjust the centre convergence, or the overall. The inner
most magnets are for doing the purity set-up, and the outer two groups
are for the R,G and then the B,R. These are very critical to adjust
and take a lot of practice. The purity set-up will interact a little
with the convergence magnets when moved. You would have to acquire the
feel for this. I would strongly suggest using a grating generator when
doing this type of set-up.

As for the corner adjustments, they are using edge or strip magnets.
These are sort of longish looking devices that are made of a flexible
plastic that is not thermo sensitive. At the end of the plastic strip
is a small magnet. On the opposite end there is some two-way adhesive
to make it stick to the wall of the tube. This magnet is inserted down
between the yoke and tube bell at the base of the neck and manipulated
to perform the corner and side convergence. Also the purity can be
effected, and there can be some compromise to get things right.

In anycase, doing the convergence set-up is difficult if you are not
set-up for this, and do not have the necessary experience behind you.

In the case of your set, when reading your description, you may be
chasing your butt when doing the convergence. The reason is that there
are some defects with the set, rather than it being purely a
convergence problem. If you have a thermo sensitive shadowmask in the
CRT, and you are trying to set up the purity and convergence, this is
not going to be practical. There may be some increased drift as the
CRT starts to deteriate some more, which it most likely will. When
CRT's age, they can become unstable in a number of ways, including
that their emission will decrease over usage time.

I would be considering to replace the set, rather than to put time and
effort in to it. When you start messing with the convergence take the
attitude, that you will most likely be soon scraping the set.

One thing that is very important is to take care for safety issues
when working in these sets. When you are doing the convergence set-up,
you will be working very close to some seriously high voltages, that
have enough current source behind them to cause severe burns, and or
injury. These adjustments must be done with the set running, and
properly warmed up.

In the learning stage, the technical people doing this type of work
are working under close supervision. An experienced tech usually will
not work alone when doing this type of work. There is always the
opening for an accident. It is part of the job. I have been doing this
type of work for more than 30 years. I have had a few good zaps from
sets. A number of times over the years that I worked in the service
centres, I've seen someone badly hurt, who thought that they knew what
they were doing.


In that case, about how much am I looking to pay for repairs and is it
even worth it to do so? Thanks again for your help!