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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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#1
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Picture tube degaussing
My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It
suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? |
#2
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Picture tube degaussing
"Ron Weston" Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? ** You sure the internal de-gaussing is still working OK ?? .... Phil |
#3
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Picture tube degaussing
On Thu, 22 Apr 2010 00:01:33 -0400, Ron Weston wrote:
My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? Any young children? |
#4
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Picture tube degaussing
Hi Ron,
Ron Weston wrote: Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? Any nearby lightning strikes? |
#5
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Picture tube degaussing
On Wed, 21 Apr 2010 23:26:59 -0500, AZ Nomad
wrote: On Thu, 22 Apr 2010 00:01:33 -0400, Ron Weston wrote: My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? Any young children? Absolutely, highly magentized small/young children mess up TV sets all the time! g But in addition to young children (with their magnetized toys) any nearby lightning strikes? And as Phil says, you should check the built-in degaussing coil. And yes, do the sides of the set near the face of the CRT. |
#6
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Picture tube degaussing
I'm wondering if a bit of banging might help. But it's not clear how, "just
sitting around", the shadow mask might have gotten deformed. |
#7
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Picture tube degaussing
On Thu, 22 Apr 2010 05:23:59 -0700, William Sommerwerck wrote:
I'm wondering if a bit of banging might help. But it's not clear how, "just sitting around", the shadow mask might have gotten deformed. The "tool" I used to use for massive degausing was a bulk tape eraser. |
#8
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Picture tube degaussing
On Apr 22, 6:49*am, PeterD wrote:
On Wed, 21 Apr 2010 23:26:59 -0500, AZ Nomad wrote: On Thu, 22 Apr 2010 00:01:33 -0400, Ron Weston wrote: My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? Any young children? Absolutely, highly magentized small/young children mess up TV sets all the time! g But in addition to young children (with their magnetized toys) any nearby lightning strikes? And as Phil says, you should check the built-in degaussing coil. And yes, do the sides of the set near the face of the CRT.- Hide quoted text - - Show quoted text - can you hear the degaussing action when you first turn the set on after it has been off for several minutes? |
#9
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Picture tube degaussing
On Apr 22, 6:20*am, AZ Nomad wrote:
On Thu, 22 Apr 2010 05:23:59 -0700, William Sommerwerck wrote: I'm wondering if a bit of banging might help. But it's not clear how, "just sitting around", the shadow mask might have gotten deformed. The "tool" I used to use for massive degausing was a bulk tape eraser. and in a pinch, use a cheap electric pencil sharpener. Those motors produce a lot of field But always, always be careful of deforming the internal screen! |
#10
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Picture tube degaussing
Hi!
Have your friend hide the magnets from the kids. The internal degauss should take care of the remaining spots provided it works. Sometimes it isn't stout enough to do the job. Some years back, my younger brothers managed to put a faint "blob" on a MAG Innovision 17" CRT. No amount of degaussing with the monitor's built in coil would do the job. Even though the coil came on at every power up, it just didn't seem to have the oomph. Operating it manually through the monitor's menu did not help. Being busy at the time, I took a quick look and decided that they'd damaged the monitor's picture tube. And then, after a while, I managed to acquire a large electric bulk eraser, which I eventually decided to try using as a degaussing wand for this monitor. It worked brilliantly. I started from several feet away by turning it on and moved very slowly toward the CRT itself. Then I ran it slowly around the CRT face, maintaining several inches worth of distance. When I was satisfied, I moved away the same several feet and shut the coil off. William |
#11
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Picture tube degaussing
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#12
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Picture tube degaussing
Thanks for the replies so far. My friend is a senior citizen and lives
alone, so no children have been near the TV. There have been lightning storms so that may be what caused her TV problem. I have a bulk tape eraser. When I visit again first I'll try my degaussing coil on the side of the TV as well as the front, and if that doesn't work I'll try the eraser. I'll report back what happens. Ron Weston wrote: My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? |
#13
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Picture tube degaussing
Some 'bulk erasers' spin a magnet using an electric motor.
Zenith once made one with a small magnet you spun by hand. It was intended for small blotches. |
#14
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Picture tube degaussing
On Thu, 22 Apr 2010 14:47:11 -0400, Ron Weston wrote:
Thanks for the replies so far. My friend is a senior citizen and lives alone, so no children have been near the TV. There have been lightning storms so that may be what caused her TV problem. I have a bulk tape eraser. When I visit again first I'll try my degaussing coil on the side of the TV as well as the front, and if that doesn't work I'll try the eraser. With the eraser, turn it on and off at least 5' away from the TV. Walk slowly to the tv waving it around then back off. Be careful; the things are very powerful and you might be able to damage the shadow mask if you get closer than needed. |
#15
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Picture tube degaussing
"William R. Walsh" wrote in message ... Hi! Have your friend hide the magnets from the kids. The internal degauss should take care of the remaining spots provided it works. Sometimes it isn't stout enough to do the job. Some years back, my younger brothers managed to put a faint "blob" on a MAG Innovision 17" CRT. No amount of degaussing with the monitor's built in coil would do the job. Even though the coil came on at every power up, it just didn't seem to have the oomph. Operating it manually through the monitor's menu did not help. Being busy at the time, I took a quick look and decided that they'd damaged the monitor's picture tube. And then, after a while, I managed to acquire a large electric bulk eraser, which I eventually decided to try using as a degaussing wand for this monitor. It worked brilliantly. I started from several feet away by turning it on and moved very slowly toward the CRT itself. Then I ran it slowly around the CRT face, maintaining several inches worth of distance. When I was satisfied, I moved away the same several feet and shut the coil off. William Back in't' day, we wuz taught to have the TV switched on, and go around the four sides of the CRT using circular motions, and to keep those motions going all the same way. Then to come up to the CRT face, and again use circular motions, again keeping them in the same direction, and spiraling slowly away from the face. At a distance of a couple of feet, when the field from the coil was no longer having any noticeable effect on the picture, the coil was quickly turned through 90 degrees, and powered off. As to what caused the problem on this particular TV, could be all sorts of things. One of the favourites, as I recall, was customers switching off the vacuum cleaner when near to the TV. You can also get suddenly appearing purity patches from shadowmask displacement when the spring expansion mounts move out of place, or spot welds on the shadowmask frame give out. However, mechanical issues such as these, would not reasonably be expected to cure by manually degaussing, so I would say that the problem here is magnetic. Arfa |
#16
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Picture tube degaussing
On Apr 22, 1:47*pm, Ron Weston wrote:
Thanks for the replies so far. My friend is a senior citizen and lives alone, so no children have been near the TV. There have been lightning storms so that may be what caused her TV problem. I have a bulk tape eraser. When I visit again first I'll try my degaussing coil on the side of the TV as well as the front, and if that doesn't work I'll try the eraser. I'll report back what happens. Ron Weston wrote: My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened?- Hide quoted text - - Show quoted text - Just be sure to m,ove at least 10 feet away before shutting it off. |
#17
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Picture tube degaussing
On Thu, 22 Apr 2010 00:01:33 -0400, Ron Weston wrote:
My friend has an inexpensive 9-inch TV, about 6 to 10 years old. It suddenly developed two green spots on the screen, one in the upper right corner and one in the lower right corner. I have a "GC Electronics Professional Degaussing Coil" and I made two attempts to degauss the TV picture tube. After the second try the lower green spot was just about gone, and the upper spot is much smaller but can still be seen. I'm going to try again next week and I would like some advice. In my attempts so far I moved the degaussing coil around only the front of the TV. Should I try degaussing the sides, top or back of the TV, or might this make things worse? Nothing unusual happened to cause the green spots. The TV hasn't been moved in years and no magnets were placed near the TV. Any theories about what happened? Did someone move some leaky speakers nearby? -- Boris |
#18
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Picture tube degaussing
I used my degaussing coil on the TV again today. This time I moved the
coil over the front, sides and top of the TV. There's still a tiny bit of green in one corner (you have to look closely on a very light screen to see it) and my friend is satisfied and didn't want me to try the bulk eraser. I'm afraid the degaussing circuit in the TV is not working. The green spots got worse in the week since I first degaussed the set. My friend is unwilling to give up her TV now so that I can repair it, but when she goes on vacation this summer I will repair the set. Thanks again for all the responses and advice. It's greatly appreciated. Ron Weston wrote: Thanks for the replies so far. My friend is a senior citizen and lives alone, so no children have been near the TV. There have been lightning storms so that may be what caused her TV problem. I have a bulk tape eraser. When I visit again first I'll try my degaussing coil on the side of the TV as well as the front, and if that doesn't work I'll try the eraser. I'll report back what happens. |
#19
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Picture tube degaussing
"Ron Weston" wrote in message ... I used my degaussing coil on the TV again today. This time I moved the coil over the front, sides and top of the TV. There's still a tiny bit of green in one corner (you have to look closely on a very light screen to see it) and my friend is satisfied and didn't want me to try the bulk eraser. I'm afraid the degaussing circuit in the TV is not working. The green spots got worse in the week since I first degaussed the set. My friend is unwilling to give up her TV now so that I can repair it, but when she goes on vacation this summer I will repair the set. Thanks again for all the responses and advice. It's greatly appreciated. Just another little bit of friendly advice Ron - don't top-post ! It's greatly frowned upon in newsgroups, and whilst it's reasonably tolerated on this group, doing it on some others will cause a shed-load of abuse to fall onto your head ... Arfa |
#20
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Picture tube degaussing
"Ron Weston" I'm afraid the degaussing circuit in the TV is not working. ** Now he tells us ...... Did he never guess that the failure of the degaussing circuit CAUSED the green patches to appear ?? ...... Phil |
#21
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Picture tube degaussing
On Apr 25, 8:15*am, Meat Plow wrote:
On Sun, 25 Apr 2010 12:41:11 +1000, "Phil Allison" wrote: "Ron Weston" I'm afraid the degaussing circuit in the TV is not working. ** *Now he tells us ...... Did he never guess that the failure of the degaussing circuit *CAUSED *the green patches to appear ?? I wonder how someone who would ask these question about degaussing determine the internal degauss wasn't working? I had a TV with a failed degaussing system which caused a serious color blotch as Phil described. This one failed because of a relay contact flexing the solder joint on the PCB which eventually failed. I removed all the old solder and re-soldered it. It went 8 years before the first failure. G² |
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