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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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I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides.
The bend is from both sides but the bend from the right side is comparatevely more than on left side. In most pictures, the bend is not noticeable but in certain pictures (like in which have got large box almost the same size of screen area or got straight line on the sides, the curve is clearly noticeable) A Sony technician had came to fix another fault of low brightness in this TV and repaired the fault by detecting a small faulty component. After that when I told about this picture curving fault, he without doing any testing told me something about yoke and that he cannot rectify this fault. My questions So, what are the possible reasons for this fault? If due to a faulty component, which is that component? Could this be corrected by some adjustments? All that the Sony engineer told me could really be true that its certainly a yoke problem? (earlier this engineer, for low brightness told me that this problem is due to faulty IC. But later he made a more detailed check and found out that a faulty resistor was responsible for that brigtness problem.. Not the IC!) Pls help Thanks R Solomon |
#2
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#4
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![]() "Tom Miller" wrote in message ... "Maynard A. Philbrook Jr." wrote in message ... In article , says... I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides. The bend is from both sides but the bend from the right side is comparatevely more than on left side. In most pictures, the bend is not noticeable but in certain pictures (like in which have got large box almost the same size of screen area or got straight line on the sides, the curve is clearly noticeable) A Sony technician had came to fix another fault of low brightness in this TV and repaired the fault by detecting a small faulty component. After that when I told about this picture curving fault, he without doing any testing told me something about yoke and that he cannot rectify this fault. My questions So, what are the possible reasons for this fault? If due to a faulty component, which is that component? Could this be corrected by some adjustments? All that the Sony engineer told me could really be true that its certainly a yoke problem? (earlier this engineer, for low brightness told me that this problem is due to faulty IC. But later he made a more detailed check and found out that a faulty resistor was responsible for that brigtness problem. Not the IC!) Pls help Thanks R Solomon Get a new TV.. 19 years is more than enough .. Picture tube is most likely a little weak, low brightness and the tech most likely cranked up the HV to compensate. Now you have to much voltage and it pushing the picture in on the side.. The other possible problem could be a bad HV regulator circuit and thus a hacked job was done. But either way, the tube is weak,... and you'll never get the correct video with out some HV issues. These HV issues will cause problems like your seeing.. The proper way to fix an old weak tube is the but a filament booster on it ? ![]() As far as know, they don't even make CRT's for consumer TV's any more. Jamie That and I am sure you could run down to Walmart and pick up a new flat screen 32 inch TV for way more than a new tube would cost just in labor alone. It would also be much more efficient and save on your electric bill. And be able to receive off the air with out a converter. That should be "way less than". I don't know what's wrong with my keyboard. It keeps typing things wrong. |
#5
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#6
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#7
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On Monday, August 4, 2014 3:14:15 PM UTC-7, Maynard A. Philbrook Jr. wrote:
In article , says... I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides. The bend is from both sides but the bend from the right side is comparatevely more than on left side. In most pictures, the bend is not noticeable but in certain pictures (like in which have got large box almost the same size of screen area or got straight line on the sides, the curve is clearly noticeable) A Sony technician had came to fix another fault of low brightness in this TV and repaired the fault by detecting a small faulty component. After that when I told about this picture curving fault, he without doing any testing told me something about yoke and that he cannot rectify this fault. My questions So, what are the possible reasons for this fault? If due to a faulty component, which is that component? Could this be corrected by some adjustments? All that the Sony engineer told me could really be true that its certainly a yoke problem? (earlier this engineer, for low brightness told me that this problem is due to faulty IC. But later he made a more detailed check and found out that a faulty resistor was responsible for that brigtness problem. Not the IC!) Pls help Thanks R Solomon Get a new TV.. 19 years is more than enough .. Picture tube is most likely a little weak, low brightness and the tech most likely cranked up the HV to compensate. Now you have to much voltage and it pushing the picture in on the side.. The other possible problem could be a bad HV regulator circuit and thus a hacked job was done. But either way, the tube is weak,... and you'll never get the correct video with out some HV issues. These HV issues will cause problems like your seeing.. The proper way to fix an old weak tube is the but a filament booster on it ? ![]() As far as know, they don't even make CRT's for consumer TV's any more. Jamie You don't do this work for a living, do you? CRTs are no longer available so when it croaks, that's it. Nobody changed the EHT as it would cause a HOST of problems. Increasing the G2 Voltage would bring up the cathode currents (brighter) but also have negative results with color tracking. It would NOT cause geometric distortions. Bad caps in the pincushion section would definitely cause geometric problems collapsing vertical lines inward. This is a VERY common Sony failure and I've replaced MANY caps. The suggestion to replace the TV is good and you'll wonder why you waited so long as the improvement is dramatic. Good riddance to CRTs. G² |
#8
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#9
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On Monday, August 4, 2014 11:29:27 AM UTC-4, wrote:
I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides. Sonys are notorious for borderline geometry issues due to CRT/yoke design, but mostly with the larger CRTS. Sudden changes in geometry are usually due to a pincussion circuit failure, but does this smallish model even have a pincussion circuit? If the distortion is not excessive, I suggest living with it if the picture is as otherwise good as you've described it. Even at 20 years old, it's still likely to survive longer than a low end Chinese TV. (Right now I have a 2013 "black friday" Westinghouse 32 with 7 LEDs burned out in the display, and no replacements available). And if running a non-HD signal into it, it will probably have a crisper, more pleasing picture than a cheap flat will. If you plan to move to HD, then the old Sony couldn't keep up. |
#10
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I had this fault in a similar set and it was a small square plastic capacitor next to the HOT. Sorry, can't be more specific.
In my opinion CRT has better color rendering and crisper picture in SD TV and uses approximately the same power to run as a modern set since both technologies are quite efficient. Just look at the specs, a big 28"CRT draws 95W of power, a similar size LCD can go up to 130W. Going HD on a CRT is not impossible, I did some experiments years ago and could get up to 1920x576 resolution on a standard TV. It requires a Scart input with RGB capability (I belive it is not common in America but it is in Europe). Using RGB you can send any horizontal resolution you want and most sets I tested actually displayed that level of detail fine (of course native 50Hz sets, not line doubled 100Hz ones). The vertical resolution is limited by the scan circuits so we can call that almost-HD. Commercial HD decoders with Scart RGB outputs can output all horizontal resolution but I do not know if all of them actually do. |
#11
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![]() Jeroni Paul wrote: Going HD on a CRT is not impossible, I did some experiments years ago and could get up to 1920x576 resolution on a standard TV. There are CRT monitors that will do 2048 * 1536. I had one HP that did. -- Anyone wanting to run for any political office in the US should have to have a DD214, and a honorable discharge. |
#12
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"There are CRT monitors that will do 2048 * 1536. I had one HP that
did. " At what refresh ? Anything over 60 Hz I want the part number of its horizontal output. Bet it was a MOSFET. |
#13
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First of all, this is SCI.ELECTRONICS.REPAIR, not SCI/ELECTRONICS.BUYANEWONE. If someone wants to buy a new one, they are not here.
Now that that's out of the way, alot of Sonys have this coil, that due to its construxtion, fails. I believe it has a magnet in it and is a saturable reactor that is used for horizontal linearity correcti90n. At least it is in alot of them. AStarting with the FSTs, when they became 20 and 27 inch rather than 19 and 26. Many many of them had such a coil especially up into the 1990s. Seems like they tried not to use them because of the obvious cost, and the fear of them failing under warranty. This coil has a cor that has a specific level, and even curve at which it gets to magnetic saturation, and the magnet's strength is calibrated. Too much heat, gone. Also, these things tend to fail on the shorted direction but they really do not short. I think in most cases the coresa get sort of pulverized and lose there ability to be a good core for an inductor. Then the coil is running into air, and because the circuit uses feedback like the more modern vertical circuit, it is not noticable to the used until it pulls so much current that is ablows the pincushion modulator, which is what straightens the sidess of your raster. The working of this circuit, in the larger deflection angles that came later, with the use of this system, actually caused a bent so bad that a vertical line owuld be bnowed, so they added parameters to the chip for bow which applies a parabola at the vertical rate to the horizintal AFC feedback loop. Some sets even had to have a separate correction for one side only because they could not work out all the nonlinearity. Reactive scanning was a real bitch in heat when it came to totally flat screens like at 40 inches and ****. All that weight is not just the tube, some is what it takes to drive the ****er. Also, I have some Sony OEM parts but I really doubt I have what you need. In the whole lot I only have a few coils. OH ! In those sets, don't run them like that. When you get that problem the horizontal is liable to fry because it ain't right. Peak currnts too high, or voltage. ALSO, get a cap checker and check every cap off the, ;no, offf ANY terminals of the horizontal output. These are critical, and can also cause the failure of the pincusion output as well. I don't know what you know right now, but htink of this as a CB radio final.. Look it up if you ain't familiar./ ANY fault in the circuitry there will cause a high SWR and make things fry. It is all a matter of timing. Something does not have to be shorted to fry the thing. It is not an audioo amp. So I say at least do not run it. And if you don't know how and wanbt to fix it, well you are in for an education. It ain't so bad. And anther thing, in SOME cases a bad lytic can cause this. You havee to lookk at it, look for signes of overheating, bulging caps, all that. **** buying a new one. That's what you did last time. not SCI.ELECTRONICS.LANDFILL. |
#14
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OK, Repairworld has nothing on it but a CX1214 chip, that ain't it.
But not I see this is a multisyste unit ? Ho boy, that is always fun in the horizontal circuit. |
#15
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#16
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On Tuesday, August 5, 2014 10:05:04 PM UTC-4, wrote:
First of all, this is SCI.ELECTRONICS.REPAIR, not SCI/ELECTRONICS.BUYANEWONE. If someone wants to buy a new one, they are not here. Now that that's out of the way, alot of Sonys have this coil, that due to its construxtion, fails. I believe it has a magnet in it and is a saturable reactor that is used for horizontal linearity correcti90n. At least it is in alot of them. Hmmmm.. that reminded me of something. It's been a long time since I've done any significant repair on CRT Sonys, but didn't they have that inductor that you speak of have a ferrite piece glued in place on top of the coil? Perhaps during a previous repair, the old dried adhesive just let go of the ferrite cap. |
#17
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Is there a "pincushion" adjustment on the set, I am on travel so don't have access to any of my manuals.
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#18
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On Monday, August 4, 2014 10:29:27 AM UTC-5, wrote:
I've got a 19 years old 21" Sony CRT TV. Model- KV2167MT. Althought the picture quality is excellent, I've recently noticed that the picture has got slightly curved inwards from the sides. The bend is from both sides but the bend from the right side is comparatevely more than on left side. In most pictures, the bend is not noticeable but in certain pictures (like in which have got large box almost the same size of screen area or got straight line on the sides, the curve is clearly noticeable) A Sony technician had came to fix another fault of low brightness in this TV and repaired the fault by detecting a small faulty component. After that when I told about this picture curving fault, he without doing any testing told me something about yoke and that he cannot rectify this fault. My questions So, what are the possible reasons for this fault? If due to a faulty component, which is that component? Could this be corrected by some adjustments? All that the Sony engineer told me could really be true that its certainly a yoke problem? (earlier this engineer, for low brightness told me that this problem is due to faulty IC. But later he made a more detailed check and found out that a faulty resistor was responsible for that brigtness problem. Not the IC!) Pls help Thanks R Solomon Go to you nearest Good Will. People are always donating old crt TV's. You may get lucky and find a 21 inch Sony picture tube. I drove by our Good Will and they had 40 crt tv's |
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