What causes the horizontal transistor to short? flybak ok, supply line ok. my tv is a samsung with a model #: ct-21k30mh.
You just replace the capacitor fitted very near to the horizontal output transistor,[freewheeling capacitor], there may be one or two of them, whcih comes to a value of 3900pf to 6700pf 2000V or so. It is connected to the negative rail and the collector of the horizontal output transitor. If it gets opened, or its value gets reduced, this fault will occur. If so the transistor you replace will get shorted as you swich on the power to TV.
The second one is deflection yoke short. If so the transistor said above will overheat within seconds. Even a single winding inside the horizontal deflection yoke shors, it puts a tremendous load to flyback transformer, which in turn effects the transistor.
After replacing the above said capacitor, you do one thing to make sure about whether there is a short inside the yoke or not. It cannot be measured by normal methods. Fore that, unplug the base card from picture tube and place it somewhere near without getting any of its contacts to other parts inside your TV. This time only the EHT chord will be connected to picture tube. Unplug the horizontal yoke connection from main board. Switch on the tv, and wait for some time, say at about 10 seconds, and check whether the transistor gets overheated or not If it does overheats now also, the winding or EHT retifier diodes inside your flyback transformer has some trouble, and it should be replaced with same type and number. If it does not overheats now, the deflection yoke's winding have some short in it. Ok.
NB: Never connect the TV with base card is in postion while deflection yoke connection is isolated. keep it unpluged.
Oct 27, 2010 |
Samsung Ultra SlimFit 20" Digital TV