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. |
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. |
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. :) --- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
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. |
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 |
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? |
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. |
Moire effects on new TV
I would suggest returning the set, if it's possible to do so.
|
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 |
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. |
Moire effects on new TV
William Sommerwerck wrote: I would suggest returning the set, if it's possible to do so. Do you think it's a problem with this particular TV or a problem with that particular model? If I exchange it for the same model, do you think that one would have problems too? The only bad review I've read for this model didn't even have anything to do with the tv, it was the user's fault. |
Moire effects on new TV
William Sommerwerck wrote:
I would suggest returning the set, if it's possible to do so. Do you think it's a problem with this particular TV or a problem with that particular model? If I exchange it for the same model, do you think that one would have problems too? The only bad review I've read for this model didn't even have anything to do with the TV, it was the user's fault. As I can't see the set, I can't pass judgement on whether the problem is a sample defect, or a persistent problem with that model. But this is a case of "one strike and you're out". I'd find a different model. If you insist on sticking with this model, then insist on opening the replacement and viewing it long enough to confirm it doesn't have the same problem. |
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