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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Old October 24th 07, 10:46 PM posted to sci.electronics.repair
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Default Moire effects on new TV

What would be causing a Moire effect on a new CRT SDTV? There are
smally wavy lines that appear on the middle sides of the tv. I'm
pretty sure they're moire effects. They only appear in a spot that's
maybe 2-3 inches in diameter.

The tv is a 27" flatscreen that's 480i. The tv is connected to the VCR
via coaxial cables and the VCR is then connected to the digital cable
box via coaxial cables. The cable signal/reception isn't all that
great and I get horizontal wavy lines on some analog channels. I think
the moire effects also appear when watching a dvd through composite
cables.

There are no signs of electrical interference.

Even though the tv is a flatscreen, it seems to cave in a bit on the
sides. Older CRTs caved out on the sides.

Do the moire effects mean the tv is defective? Is it something that
will get worse with time? I suppose I want to know if it should be
returned? It doesn't bother me as I hardly notice. I just don't want
to get stuck with a defective tv.


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Old October 24th 07, 10:50 PM posted to sci.electronics.repair
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Default Moire effects on new TV

Is this on every channel? On every program?

Does it appear in every image? Moire patterns would normally appear only in
areas with a lot of fine detail.

One possible source of moire patterns is the use of a 625-line tube in a
525-line set, or vice-versa.


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Old October 25th 07, 12:14 AM posted to sci.electronics.repair
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Default Moire effects on new TV

"William Sommerwerck" writes:

Is this on every channel? On every program?

Does it appear in every image? Moire patterns would normally appear only in
areas with a lot of fine detail.

One possible source of moire patterns is the use of a 625-line tube in a
525-line set, or vice-versa.


Huh? A 625 line tube? Perhaps you should clarify.

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Old October 25th 07, 12:57 AM posted to sci.electronics.repair
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Default Moire effects on new TV

"Sam Goldwasser" wrote in message
...
"William Sommerwerck" writes:


One possible source of moire patterns is the use of a 625-line tube
in a 525-line set, or vice-versa.


Huh? A 625line tube? Perhaps you should clarify.


This isn't a joke.

Think of the way a shadow mask has hundreds of thousands of tiny holes,
spaced at some particular pitch. Now imagine those whole "interfering" with
the scanning lines in the image, producing a moire.

I first learned of this about 25 years ago, when I viewed the then-new
Proton TVs. Proton was using CRTs with a dot-pitch suitable for a 625-line
system in 525-line TVs, to get better horizontal resolution. Unfortunately,
this sometimes produced moire patterns.


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Old October 25th 07, 01:51 AM posted to sci.electronics.repair
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Default Moire effects on new TV

svu geek wrote:
What would be causing a Moire effect on a new CRT SDTV? There are
smally wavy lines that appear on the middle sides of the tv. I'm
pretty sure they're moire effects. They only appear in a spot that's
maybe 2-3 inches in diameter.

The tv is a 27" flatscreen that's 480i. The tv is connected to the VCR
via coaxial cables and the VCR is then connected to the digital cable
box via coaxial cables. The cable signal/reception isn't all that
great and I get horizontal wavy lines on some analog channels. I think
the moire effects also appear when watching a dvd through composite
cables.

There are no signs of electrical interference.

Even though the tv is a flatscreen, it seems to cave in a bit on the
sides. Older CRTs caved out on the sides.

Do the moire effects mean the tv is defective? Is it something that
will get worse with time? I suppose I want to know if it should be
returned? It doesn't bother me as I hardly notice. I just don't want
to get stuck with a defective tv.

Degaussing Problem ???
Because it appears in a spot about 3" in diameter
This is a LOCAL problem affecting Convergence , on a small percentage of
the Screen
Unplug the set off for about 10-15 minutes then turn back on ! Repeat
several times to allow the built-in Degaussing circuit to cycle several
times. You have to let the Thermistor in the Degaussing circuit Cool
down, between restarts
Moire effects are usually caused by AC fields.
Look around for the source of the magnetic field, transformers, fans,
motors. powerpacks and chargers, speakers.

If all else fails return the set !

The Barrel Distortion may be an Optical illusion. ie. Barrel distortion
on older CRTs' and Pincushioning on Flatscreens even after correction.

Yukio YANO


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Old October 25th 07, 06:34 AM posted to sci.electronics.repair
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Default Moire effects on new TV


William Sommerwerck wrote:
Is this on every channel? On every program?

Does it appear in every image? Moire patterns would normally appear only in
areas with a lot of fine detail.

One possible source of moire patterns is the use of a 625-line tube in a
525-line set, or vice-versa.




It's mostly noticable on darker screens/images. If I try to spot it on
the lighter screens I sometimes can. I think it did appear when
watching a dvd through composite cables and it appeared while watching
a videotape through coaxial cables.

One thing I noticed about this tv is that even though the picture sort
of looks better than older CRTs, it also doesn't look as crystal
sharp. It's weird. But then I still think my old CRT monitor looks
better than these new LCD monitors, which is partially why I chose a
CRT tv over an LCD tv.

Anyway, the tv is a Sanyo and the model number is HT27547. Do you
perhaps know anything about this particular model? Is there anyway you
(or anyone) could find out anything about it?

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Old October 25th 07, 07:40 AM posted to sci.electronics.repair
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Default Moire effects on new TV

With very sharp beam focus it is possible to have Moiré effect. In a simple
explanation, the scanning lines are very thin, and causing a type of optical
beating effect with the rows and columns of the phosphor dots in the
shadowmask.

With a Trinitron tube, the Moiré effect can occur with the horizontal scan
axis. This is because the mask is vertically striped.

With a standard shadowmask, the Moiré effect can occur both vertically and
horizontally.

Sometimes the service tech would adjust the beam focus to be a little less
sharp to mask this effect. This would give a softer picture.

In the higher end CRT TV sets, they had a Moiré filter. What this did was
use some active filter circuits as part of the video processor design to
filter out the bandpass of video response in the range that can produce the
Moiré effect. This allows for sharp beam focus with this effect reduced.

Many high end computer monitors have in their menu, an adjustable Moiré
setup. This allows the user to filter or not filter it. When filtering
anything, some response is taken away. There are tradeoffs for everything.

Have you considered an LCD or Plasma display? They cannot have Moiré
effect, and there are no convergence or purity errors possible.

--

JANA
_____


"svu geek" wrote in message
ups.com...
What would be causing a Moire effect on a new CRT SDTV? There are
smally wavy lines that appear on the middle sides of the tv. I'm
pretty sure they're moire effects. They only appear in a spot that's
maybe 2-3 inches in diameter.

The tv is a 27" flatscreen that's 480i. The tv is connected to the VCR
via coaxial cables and the VCR is then connected to the digital cable
box via coaxial cables. The cable signal/reception isn't all that
great and I get horizontal wavy lines on some analog channels. I think
the moire effects also appear when watching a dvd through composite
cables.

There are no signs of electrical interference.

Even though the tv is a flatscreen, it seems to cave in a bit on the
sides. Older CRTs caved out on the sides.

Do the moire effects mean the tv is defective? Is it something that
will get worse with time? I suppose I want to know if it should be
returned? It doesn't bother me as I hardly notice. I just don't want
to get stuck with a defective tv.


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Old October 25th 07, 11:53 AM posted to sci.electronics.repair
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Default Moire effects on new TV

I would suggest returning the set, if it's possible to do so.


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Old October 25th 07, 08:36 PM posted to sci.electronics.repair
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Default Moire effects on new TV

On Oct 24, 4:57 pm, "William Sommerwerck"
wrote:
"Sam Goldwasser" wrote in message

...

"William Sommerwerck" writes:
One possible source of moire patterns is the use of a 625-line tube
in a 525-line set, or vice-versa.

Huh? A 625line tube? Perhaps you should clarify.


This isn't a joke.

Think of the way a shadow mask has hundreds of thousands of tiny holes,
spaced at some particular pitch. Now imagine those whole "interfering" with
the scanning lines in the image, producing a moire.

I first learned of this about 25 years ago, when I viewed the then-new
Proton TVs. Proton was using CRTs with a dot-pitch suitable for a 625-line
system in 525-line TVs, to get better horizontal resolution. Unfortunately,
this sometimes produced moire patterns.


Wanna buy a bridge? How do you explain dual standard monitors? I
assure you I don't change out the CRT to change from PAL to NTSC. The
odds are much higher that the 'moire' is from the Y/C separation in
the monitor. If a DVD is played into the monitor/TV using _component_,
there would be no separation as the signal was never encoded. If the
moire is present then, THEN I'll buy CRT explanations.

GG

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Old October 25th 07, 08:45 PM posted to sci.electronics.repair
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Default Moire effects on new TV

svu geek wrote in news:1193262366.747801.26640
@i38g2000prf.googlegroups.com:

Even though the tv is a flatscreen, it seems to cave in a bit on the
sides. Older CRTs caved out on the sides.


Optical illusion. You are used to the CRT bowing out. It is a change to see
it appear to bow in. You'll grow accustomed to it.


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