Friend gave us a toshiba a3642 tv,the screen is green,is this worth fixing?
Your TV is has no green cathode voltage at the picture tube pin. There are three electron guns for every colur picture tubes, Red, Blue and Green. These three guns together mixes all colours we see on the screen. If any one of them happen to be not working properly, that colour must either be lack, of excess. Voltages at the above said three colour cathodes are somewhat equal to each other. if voltage goes down, the emission of that particular cathode will rise, and as a result that colour will be predominent on the screen.
These cathodes are fed voltages from the video output stage of your Tv. This stage can be located at the neck of the picture tube itself, as a card pluged onto it, called the base card. There will be either three trasistors to drive the each above said three cathodes, in some sets, there will be independent three ICs or only one IC capabale of driving these three catodes will be used.
You just open your TV, after unpluging it from the wall power socket. You can locate the above said base card, at the neck of the picture tube. Before doing anything, check very keenly for any loose solderings are there on the CRT base board. It is very difficult to locate the loose solderings, as they may be microscopic in size. So I advice you to resolder all the soldering points on that board, by applying a little more solder, without making any short circuit bridges in between.
In most cases. this will solve the problem. If not, check the voltages at the above said three cathode, wheere tey were marked on the PCB itsef as R ,G & B. You can see that the green cathode voltage of your set will be much lower than the other tow, in your TVs case. If so, check the resistor connected to the revalent Ic or transistor, whichever it may be, for open circuit. that is check whether it has burned or not. If that resistor is Ok, replace the transistor or IC, which drive the green cathode.
If you wants furthermore assistance, feel free to get me through Fixya. OK.
Dec 15, 2010 |
Toshiba 36A42 36" TV