Picture on Panasonic tv intermittently becomes striated and bottom half of picture shows on top half of screen
I recently bought a Panasonic tv (28 or 32 inches, non-flat screen) from a thrift store, and it seems in very good condition. Sometimes a movie will play all the way through fine, but frequently the picture becomes striated and flickers, and the bottom part of the picture will show on the top third of the screen. The effect resembles when the tracking on a VCR is off (except the picture doesn't scroll up or down). Any help or ideas given would be greatly appreciated! Thanks!
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Re: Picture on Panasonic tv intermittently becomes...
What you're describing sounds like a vertical deflection problem if it also occurs when you're watching a TV program. This type of trouble is a component failing in the vertical circuit of your set. A loose solder connection could cause this.
On the other hand, if it just happens when you run the VCR, your problem could be somewhere in the tape drive mechanism or possibly a bad tape. Things like slipping clutches,bad belts sticking guide rollers are a few things that will cause this in a VCR.
You need to have a tech check it for you.
Hope this gives you some help.
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do the proper isolation proceedure and try unhooking the Su from the SC board to see if you then get a normal picture all the way across the bottom half of the screen? I am assuming the Vertcal extends extends all the way from top to the bottom of the screen?
hit your TV on left side or right side or on top & then observe ..........you will get normal picture or it comes & again it goes....if it is happening like that then following is the situation..........after 4 or 5 yrs in some TVs on main board ( also on CRT circuit board ) at some soldering joints crack develops....then due to loose contact picture becomes small in size or abnormal width, or rolls etc ...........when we hit that lightly then those loose contacts joins temporarly & again picture appears normally for some time............so solution is .....TV main board & CRT circuit board should be observed carefully & most of the joints should be re-soldered.......only a good service engineer can do that........even after hitting TV lightly if there is no response then main board has to be checked completely........in your case iam sure it is loose connection problem.........joints should be re - soldered ...100% it works again ................this problem cannot be solved by user unless user has idea about components( resisitors, transisitors, diodes,...etc) , have soldering iron , multimeter & other tools....................so contact good TV service engineer & just ask him to resolder joints ...........
Odds are real good that the cooling fluid in the blue picture tube assembly has become contaminated. Only solution is to pull blue crt and dump out old fluid and clean and reinstall new fluid. Once done a fair amount of re-alignment is required. This is not a job for a do-it-yourselfer. Most tv shops would charge in the area of $250 to $300 for this repair.
That is what I was going yo suggest. You can also adjust the picture size. "Just" will show all of the picture even the distortions on the edges. "Full" will in effect overscan and trim those edges off.
intermittent loss of picture on either bottom or top half of screen is specific to y buffer boards located on left side of screen going from top to bottom when looking at back of tv. the y lower buffer would be the board to replace to resolve the loss of bottom half of picture. if the top half also is going out intermittently could tied to upper buffer as well but just a note the y main board to right of these buffers drives those two boards so in some cases could also be part of the problem. if only bottom half is affected i would recommend replacing lower buffer only
There is not much for me to go on with your description but here goes,
I suppose you have a convential TV set with a glass picture tube and not one of the new types with the large screen slim style displays!!!
If it a glass type picture tube then the following assumptions are made.
I hope yopu have not shifted house recently and moved the TV around???
If you have its possible the Yoke (its a device on the neck of the Picture tube that controls magnetically the scanning dot) may have moved and only is letting you see half a picture...
This is a long shot but it could be the cause..
Now the picture is supplied to you by a fast moving dot of light (Black & White set) that scans from the top of the picture and moves very fast down to the bottom of the screen, then flys back to the top of the screen and starts all over again during this process the dot lights up the picture tube to provide you with
the picture you see... (On a colour set there are three dots)
Its quite a complex process and its all controlled by electronics inside the TV receiver.
If you are getting only half a picture then something is causing the dot to only turn on for the lower half of the picture during its write time to the glass screen,
You dont say if the half thats off is white or black, so there are many things that the service technician needs to know before even starting to look for this fault. During the dot doing its write cycle down the sceen, when it reachs the bottom and flys back to the top of the screen it receives a synchronous pulse from the TV station, and this TV signal is critical in making sure you see the same picture as is being sent from the TV station.
Sometimes this sync pulse from the TV station is very weak and so your picture may float up and down the screen trying to lock to the incoming signal.. this just may be your fault.. but you dont say if the half of the picture that you see is floating or not..
Your situation may be that your TV has partially locked to the station signal and your aerial may be problematic,
but then you dont say if its on just the one channel or all of your station channels. So there needs to be more analysis of your situation prior to a positive answer being provided....
When only a half screen is produced, it is usually a upper or lower buffer board, if the top half is blank then it is the upper buffer, and of course if it's the bottom half then it's the bottom buffer board