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| Sylvia Else... |
 Posted: Wed Nov 04, 2009 6:22 am |
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| Adrian C... |
| Posted: Wed Nov 04, 2009 8:29 am |
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Sylvia Else wrote:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
[/quote]
Faulty digital frame buffer.
--
Adrian C |
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| baron... |
| Posted: Wed Nov 04, 2009 8:36 am |
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Sylvia Else Inscribed thus:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Sylvia.
[/quote]
I've never seen a crt with a line of dead anything ! If its a dead
straight vertical line then its unlikely to be the crt. Possibly some
artifact of the video feed... maybe ?
--
Best Regards:
Baron. |
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| PeterD... |
| Posted: Wed Nov 04, 2009 8:55 am |
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On Wed, 04 Nov 2009 22:22:06 +1100, Sylvia Else
<sylvia at (no spam) not.at.this.address> wrote:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Sylvia.
[/quote]
It processes the signal as digital then converts to analog for the CRT
driver. I'd guess it is not going to be worth trying to fix, something
is gone in the digital section(s). |
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| Jim Yanik... |
| Posted: Wed Nov 04, 2009 12:16 pm |
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PeterD <peter2 at (no spam) hipson.net> wrote in
news:9t13f5h9pp3a5mkborrbkjsvjgoucj7bm0 at (no spam) 4ax.com:
[quote]On Wed, 04 Nov 2009 22:22:06 +1100, Sylvia Else
sylvia at (no spam) not.at.this.address> wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Sylvia.
It processes the signal as digital then converts to analog for the CRT
driver. I'd guess it is not going to be worth trying to fix, something
is gone in the digital section(s).
[/quote]
some chip in the frame memory?
--
Jim Yanik
jyanik
at
localnet
dot com |
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| Ron... |
| Posted: Wed Nov 04, 2009 12:21 pm |
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Jim Yanik wrote:
[quote]PeterD <peter2 at (no spam) hipson.net> wrote in
news:9t13f5h9pp3a5mkborrbkjsvjgoucj7bm0 at (no spam) 4ax.com:
On Wed, 04 Nov 2009 22:22:06 +1100, Sylvia Else
sylvia at (no spam) not.at.this.address> wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Sylvia.
It processes the signal as digital then converts to analog for the CRT
driver. I'd guess it is not going to be worth trying to fix, something
is gone in the digital section(s).
some chip in the frame memory?
Could it possibly be a stabilising wire as in the Trinitrons(I know they[/quote]
are usually horizontal)
Ron |
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| D Yuniskis... |
| Posted: Wed Nov 04, 2009 2:34 pm |
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Sylvia Else wrote:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
[/quote]
It doesn't. :> I suspect there are *two* "lines of dead
pixels" in this CRT -- though only one is probably visible
(luck?).
There are two (3?) wires that cross the screen (usually horizontally
but since this is a wider aspect ratio screen, they might be
oriented vertically) used to stabilize the aperture grill. |
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| Dave Platt... |
| Posted: Wed Nov 04, 2009 3:48 pm |
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In article <hcs008$poa$2 at (no spam) news.eternal-september.org>,
baron <baron.nospam at (no spam) linuxmaniac.nospam.net> wrote:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
I've never seen a crt with a line of dead anything ! If its a dead
straight vertical line then its unlikely to be the crt. Possibly some
artifact of the video feed... maybe ?
[/quote]
It's a Trinitron tube. This type of CRT doesn't use a shadow mask.
Instead, it uses a shadow grid - a bunch of very fine parallel
vertical wires, stretched from top to bottom.
An occasional fault in a Trinotron is for one of the shadow wires to
end up out of position. If I recall properly, this can happen if
somebody uses an external degausser - the magnetic field can shove one
wire across the one next to it. This will cause a subtle vertical
stripe to appear on the screen.,. looks rather like a row of dead
pixels.
I think there's a Field Engineering Repair procedure for this...
rapping sideways on the case, with just the right amount of force, to
jar the stuck wires apart and allow the displaced one to snap back to
its correct position. I don't know how much force is required.
One can sometimes see this effect even on a perfectly good
Trinotron tube... I think that in some models there are vertical
reinforcing rods in the grid assembly which can produce a shadow on
the tube.
--
Dave Platt <dplatt at (no spam) radagast.org> AE6EO
Friends of Jade Warrior home page: http://www.radagast.org/jade-warrior
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| Baron... |
| Posted: Wed Nov 04, 2009 4:17 pm |
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Dave Platt wrote:
[quote]In article <hcs008$poa$2 at (no spam) news.eternal-september.org>,
baron <baron.nospam at (no spam) linuxmaniac.nospam.net> wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
I've never seen a crt with a line of dead anything ! If its a dead
straight vertical line then its unlikely to be the crt. Possibly some
artifact of the video feed... maybe ?
It's a Trinitron tube. This type of CRT doesn't use a shadow mask.
Instead, it uses a shadow grid - a bunch of very fine parallel
vertical wires, stretched from top to bottom.
An occasional fault in a Trinotron is for one of the shadow wires to
end up out of position. If I recall properly, this can happen if
somebody uses an external degausser - the magnetic field can shove one
wire across the one next to it. This will cause a subtle vertical
stripe to appear on the screen.,. looks rather like a row of dead
pixels.
I think there's a Field Engineering Repair procedure for this...
rapping sideways on the case, with just the right amount of force, to
jar the stuck wires apart and allow the displaced one to snap back to
its correct position. I don't know how much force is required.
One can sometimes see this effect even on a perfectly good
Trinotron tube... I think that in some models there are vertical
reinforcing rods in the grid assembly which can produce a shadow on
the tube.
[/quote]
Dave: Thanks for those notes. I wasn't aware of the vertical wire grid
in a Trinitron tube. I knew about the two horizontal ones. I can
actually see those in my screen.
--
Best Regards:
Baron. |
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| Sylvia Else... |
| Posted: Thu Nov 05, 2009 2:13 am |
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Adrian C wrote:
[quote]Sylvia Else wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Faulty digital frame buffer.
[/quote]
I'd be surprised if a television like that had a frame buffer. What
would it be for?
Sylvia. |
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| Adrian C... |
| Posted: Thu Nov 05, 2009 5:33 am |
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Sylvia Else wrote:
[quote]Adrian C wrote:
How does a CRT end up with a vertical line of dead pixels?
Faulty digital frame buffer.
I'd be surprised if a television like that had a frame buffer. What
would it be for?
[/quote]
The set features a digital tuner.
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Adrian C |
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| Sylvia Else... |
| Posted: Thu Nov 05, 2009 5:53 am |
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Adrian C wrote:
[quote]Sylvia Else wrote:
Adrian C wrote:
How does a CRT end up with a vertical line of dead pixels?
Faulty digital frame buffer.
I'd be surprised if a television like that had a frame buffer. What
would it be for?
The set features a digital tuner.
[/quote]
Fair point. Still, if the pixels were dead only in digital reception
mode, I think the seller would have said so.
Sylvia. |
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| Bob Larter... |
| Posted: Thu Nov 05, 2009 6:48 am |
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Sylvia Else wrote:
[quote]http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
[/quote]
Good question. I've only ever seen a fault like that on an LCD panel.
--
W
. | ,. w , "Some people are alive only because
\|/ \|/ it is illegal to kill them." Perna condita delenda est
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| Samuel M. Goldwasser... |
| Posted: Thu Nov 05, 2009 8:28 am |
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Sylvia Else <sylvia at (no spam) not.at.this.address> writes:
[quote]Adrian C wrote:
Sylvia Else wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Faulty digital frame buffer.
I'd be surprised if a television like that had a frame buffer. What
would it be for?
[/quote]
It has a DTV tuner, thus it has digital storage and one or more frame
buffers.
However, I would be skeptical that a digital failure would result
in a vertical line fault in a non-flat panel TV, though might be
possible.
Has anyone contacted the seller to get a more detailed description of
the appearance of the "dead pixels" or a photo? Also, a CRT fault
will stay fixed on the screen regardlerss of the mode or any adjustments
while soemthing in the digital processing would almost cerrtainly not.
--
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Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
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| Sylvia Else... |
| Posted: Thu Nov 05, 2009 8:34 am |
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Bob Larter wrote:
[quote]Sylvia Else wrote:
http://tinyurl.com/yz3eko4
How does a CRT end up with a vertical line of dead pixels?
Good question. I've only ever seen a fault like that on an LCD panel.
[/quote]
The stuck shadow wire concept seems reasonably plausible, though I'd
expect it to produce a line of bright pixels next to the dark ones -
electrons from more than one cathode reaching the phosphor.
Sylvia. |
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