Toshiba tv i have for 5 years, the problem was tv on full screen brightness ,no sound ,no picture. but could change tv channel,see look like very dull picture, i try replace back same # flyback & memory ic that two way didnot done problem. please heip me & give me a good idea to fix up this problem .thanks
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From your detailed description, it sounds that the main chroma processor IC has damaged. Raster means nothing, but the lighted screen that appears, when a TV is switched ON. For some brands, there will be a blue screen; when there is no signal input, and some others will have a bright white screen with some snow.
I advice you to contact any service technician, to get this TV repaired. If you wish to get some details; check the site linked here. Viewing it in "Mosaic" or "Magazine" will make surf easy. Pull up older posts. Surf the site with patience. Do a search by type in the brand name of your device at its search box and press "Enter". http://electronicshelponline.blogspot.com/
First make sure that the brightness and contrast are turned up.If the screen is lit up (that is you have a raster) then the problem would be in the video circuits.If the screen is not lit then you have a problem in the deflection circuits.A good possibility,with no raster,would be the Horizontal output amplifier.If you are not familiar with circuitry you would need a tv tech.to do the repair.
1) you have problem with the Raster 2) the main causes are a) raster b) picture c) sound d) synch 3) since this are not video, the problem is raster. your must test the voltage from section horizontal out +125vdc+vertical output +80v+all other circuit +12vdc 4) test the power supply for defective. see the diagram attached
In these cases you might be able to see a
picture by shining a bright light right next to the screen front. Do not put the light there for very long or you will end up
with a permanent bright spot burt onto the screen. I have discovered that applying light pressure with a 3/8" thick rubber or
plastic shim corrects a panel inverter/driver board/card solder problem with many flat panel TVs. (Removing
the TV back is required, try light pressure against the inverter board while wearing rubber gloves and tv is then powered on.)
check the high voltage with the screen control turned up high where there is no raster. suspect problem within the video circuit where there is no high voltage or defective picture tube.some time when the screen is black and the screen control advanced,you can see if the tv has video or vertical or horizontal problems on the screen.service the high voltage circuit if there is no raster or high voltage is seen.no raster can be caused by the no heater or filament in the CRT.----
a defective picture tube can cause many problems, such as, poor brightness ,missing colors,intermittent picture,poor focus,a single-colored raster,arching in the gun assembly,retrace lines in the picture,negative picture,chassis shutdown,noheater or filament lit and no raster to name a few.an open filament or heater can cause no picture or no raster symptom.a defective CRT can have an extremely bright screen.loose particles of the cathode element can lodge between the grids and cause an intermittent black and white picture. simply tap the ends of the CRT gun assembly and notice if the picture begins to flash off and on.----
with a leaky picture tube after turn on the raster dims and get extremely bright.a dim picture with no green in the raster can result from a bad green assembly. a heater-to-cathode short can cause a raster to change colour or a result in no raster at all.replace the picture tube if there is severe arching in the neck of CRT.
excessive brightness with retrace lines and a vertical collapse to a thin line can be caused by a bad coil on the neck board of the picture tube.rejuvenate the picture tube when there is very bright green screen.
check for the resistance change on the resistors of the CRT neck board for an excessively bright picture with retrace lines.excessive dust inside the CRT spark gaps within the picture tube socket can cause the very bright raster and the chassis shutdown.a defective video amp,luminance buffer,or reference transistor can cause a bright picture with retrace lines.
for getting any required parts to replace you can get it from
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This trouble symptom picture wide or"blooming", the picture becomes dim even with the brightness control full on,and there is an abnormal enlargement of picture or raster.Usually,the enlargement is uniform,but there may be some defocusing.In some circuits,the brightness control operatesin reverse(rotating the control for an increase in brightness produces a decrease) after reaching a critical point on the control. If the picture wide is not accompanied by insufficient width(a symptom of horizontal output failure) the probable cause is a high volatge circuit ony,particularly the HV rectifier and HV winding.Any circuit problem that reduces but does not completely eliminate the high-voltage output to the picture tube second anode can cause overscan. The most likely defects are leaking high-voltage capacitors,defective high voltge tube rectifiers,leaking high voltage leads,defects in high voltage circuit protective resistance,and shorted turns in high voltage winding of the flyback transformer.
This is usualy because there is either a high voltage regulation fault, or a main power supply regulation fault.
There are many things that can cause this. When the high voltage goes too far down, the raster will enlarge. High voltage regulation can be caused by faulty components in the feedback sensing, or in the high voltage multiplier, or in the flyback windings itself.
A quick way to sort of know if the high voltage is regulating is to wind the brightness and contrast from one extreme to another and observe the raster size. If the raster is changing size with the brightness on the screen, the regulation is not working well. In some of the low cost sets there will be about a 2 to 5% raster size shift in this case. The high end sets will have a near 0% shift in the raster size. A size change of about 2% is acceptable for most sets. If the CRT is weak, this test will not work well, because a weak CRT will not properly load.
If the main power supply is operating slightly over voltage, the raster size will increase. Usualy, the brightness will be a little on the high side when the supply is too high. Voltage regulation faults can be from warn components in the voltage regulator area, or in the feedback control.
This should be looked after by an experienced TV service tech. This type of fault can be involved.
Flyback lines? Is the picture all white with no brightness control with faint horizontal faint lines? If this is what you are saying, the screen voltage could be bad, and if thats the case, the picture tube or the flyback itself could be bad. You could also have a bad connection on the crt socket