Have a Goodmans widescreen CRT TV. The set switches on, the picture starts to narrow in width at the centre line of the screen, and after a couple of minutes it starts to smoke a little. Any ideas what might be wrong? Is it worth repairing?
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Re: Failing CRT TV
Could be a couple of circuits that are failing. Something in the horizontal or the damping sections . Maybe a IC or a cap that is shorting out . If it had good brightness and good color it might be worth saving . If any of those two might be weak it might be time to scrap it . If you take it to your local repair center ask them what there estimate charge is if you don't get it fixed , as then it might be worth getting it checked out. Good luck
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Sounds like you may have just left one of the wires loose from the red tube. Not likely an issue from the gren tube but you can always cover the top of the lens and let just green shine up. That may help narrow it down also.
Here is more detailed info for you also.....
Projection TV tubes have a liquid coolant that is used to keep them from overheating. After many years the coolant in the blue and green tubes will become cloudy and cause the screen to look dull, red/orange, etc. You may even see halos around images.
Those are retrace lines, the screen controls which are a technical control located under the front gray panel of your tv needs adjusted. This also could be an indication of a bigger problem, most common would be the focus block failing. it could also be of the picture tubes failing but this is not as common or possibly the crt driver ic's. There are specific diagnositc steps to preform to isolate the potental failure. this could lead to the tv going very bright then shutting down. The first thing a tech is going to do is to adjust the screens and leave, somtimes this is enough, but sometimes it is not. if you want to try and adjust the screen i have an instruction set below, but i must warn you that there are high voltages present when attempting this adjustment and can be dangerous if you are un familure with tv repair.
Turn your color all the way down and the brightness in the middle, then
find the focus block, it will be a block with 6 controls one row will
say screen the other will say focus near the picture
tubes, adjust the screen controls(one control for each color) until the
picture has a good black and white look to it, then turn your color up
and it should look fine. This is how i balance out the picture. But
there is another method that allot of techs use, the other method is to
adjust the brightness up until you see what is called retrace lines it
is a jagged line going down the screen, once you see these lines back
the adjustment down just until they disappear. Do this for all three
colors. This method works but on an older set can throw the white
balance off because of tube wear.
The lines you saw, i;m sure they are the ones called retrace lines but know the failure could be located on the red CRT board. Most likely the video amplifier is defective and not necessarily the CRT.
What is the model number of your TV?
Without seeing the set and checking it out, this is hard to accurately tell.
The following is when a single CRT or tube in a projection TV set starts to get weak. It is the same for a CRT when any one of its electron-guns starts to go weaker than the others.
On any CRT based set either with a single CRT or with seperate projection CRT's, as the tube(s) (CRT's) get weak their emission goes down. One of the symptoms is that the beam focus gets softer.
When a CRT goes weak the beam current will decrease. This lowers the mass or intensity of the electron beam. This makes the beam width wider, and thus the image focus is softer. Having a wider beam in a single CRT or single colour section of a CRT's electron gun also means that there will be more beam width overlap in comparison to the other CRT's or the other electron-guns in the case of a single CRT. This will give the appearance of an overlap or edging especialy with sharp or thin lines.
There is also a symptom where the convergence can get less accurate as the convergence control circuits age. This means that the scan tracking between each of the CRT's or the electron-guns in a single CRT start to not be able to accurately keep converged to each other. This will produce a border effect between the beam position accross the scanning of the screen.
Sometimes with a projection CRT set if there are separate focus controls in the high voltage (HV) section for each of the colours the beam focus may be able to be cheated if the CRT is not too weak. In most CRT sets the focus voltage is shared between all the colour channels, and thus there is no possiblity to control each channel individualy.
With weak CRT's there are other factors that come in to effect. One big one is that the colour tracking gets impossible to be accurate. This is because the gain liniarity of the tube becomes out of spec. As each of the CRT's or the electron-guns in a single tube become weak they will lose their tracking accuracy in relation to each other. In the design of the drive circuits of the better TV sets there are some auto circuits to try to make sure that the tracking is stable. But, when the electron-guns become too weak the circuits run out of range.
in the front cover turn up screens on all colors till you see retrace lines, then back them down to where dissappear. enless you know the correct voltage to set it. as for the green. i would try the red crt on the green and see if it looks ok. if so then replace crt circuit or check transistors on crt circuit may also need to change the driver on the heat sync.