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Re: sharp 27" tv
ALways check for connections. Caps usally get better with heat not worse, but maybe. with out the resources of a service center id say if you suspect a cap change them all i would guess though more likely the IC or a connection becaues you say it is good cold and bad hot
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Shrinking picture is a voltage regulation problem in the switch mode power supply, Possibly a cap used in the feedback circuit. Or an over current condition on the B+. This is a very tech intense repair because there is no magic bullet. If it is shrinking on bright scenes then you can bet it is a regulation problem, bright scenes draw more current from the power supply causing this effect. I would not suspect the horiz output because the regulation for this circuit usually comes from the main switch mode power supply. One diagnostic is to monitor the B+ going to the horizontal output and see if it fluctuates. If so you can bet it is a cap or optical coupler in the switch mode circuit.
your problem is from east west ckt . there is a transformer used in this ckt which Dry solder and works inttermittent ( shrinks & expend ) . resolder this transformer . iam working with philips ......... enjoy
This is a sign that there are either bad caps in the vertical circuit or bad connections at the vertical IC. CAn you solder? If so, resolder the pins on the vertical IC first and post the results here. The vertical IC will be a small flat IC attached to a heatsink with about 9-11 pins. It may be marked LA7837 or something similar.
Initially I would suspect a problem in the Vertical section of the TV. This could either be the capacitor or the IC itself. In some instances, there are no component failures but rather cold solder joints.
Based on your post/description of :...Once in awhile picture returns to normal...", I am more inclined to think that it is a case of cold solder. which can easily be corrected by reapplying heat on the IC pins or the other associated/nearby components with the use of a soldering iron. Care must be exercised since TV units still pack high voltages even when off and unplug.
Hope this be of help/idea. Pls post back how things turned up or should you need additional information.
it is cery simple
as it folds after an hoyr or so.
as you are asking for the section where the problem is located so is in horizontal oscilattor section.(possible cause cap.might be defective.)
as per ckt diagram is concerned is concern please seeweb site
hope this will help
Usually, when a picture collapses some but not all the way, it indicates that an electrolytic capacitor has gone bad in the verrtical circuit. If the top of the picture shrinks, suspect the pump-up capacitor, but if the bottom shrinks then the coupling cap is probably going bad. This is quite an easy thing to correct, so have a qualified tech service the set.
Since Intermitant always inspect the vert ckt for bad solder connections. If not replace the output IC they're cheap and most likely the problem If you still have lines on the top or bottom I would replace all of the electrolytic capacitors in the vert ckt also. Without much test equipment rebuilding the whole little ckt is the best way to go.
All symptoms indicate a problem in the vertical circuit,the first thing to look for will be loose conection on the vertical output IC,sometimes this IC goes bad completly and it needs to be replaced.If you are familiar with soldering electronics you can take care of it but if you are not too familiar you can play it safe and take it to a servicer ,it will be a lot less expensive than if they come to your house.Let Us know how it goes or if you need more information.