Flyback transformer and horizontal output transistor change out
I am trying to change out a flyback transformer and horizontal output transistor on a RCA Scenium HDTV/DVD Monitor 52-Inch Model # D52w135D.And I need to know where do I disconnect the wires from,is it the flyback transformer and the horizontal output transistor itself,or do I disconnect it from the other end.because I can't get to the other end from where I am. And I can't seem to get them out of the flyback transformer nor the horizontal output transistor,so could you give me some advise on what i'm doing wrong.
Re: flyback transformer and horizontal output transistor...
There is a little loose sleeve at the transformer. It can be pulled out, but it is best to squeeze the sides through hole on each side of the terminal to remove the sleeve. The wire just comes out with a small pull afetr the sleeve is removed. Good luck.
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The horizontal output transistor that drives the flyback transformer overheats now. There might be other reasons too for this fault. If the flyback transformer has any internal winding short, this transistor will overheat. Just replace the horizontal output transistor. Check its heat. If the newly replaced transistor too overheats, replace the flyback transformer.
The F27442 uses the CTC203 series chassis and that symptom is very common. If the horizontal output is shorted you MUST resolder the coil in series with the base of that transistor and the pins of the small horizontal drive transformer. When they have been properly resoldered you can put in a new original horizontal output transistor. If the output transistor shorts out again then your flyback (high voltage) transformer is shorted and needs to be replaced.
The F27669 uses the CTC203 series chassis. The most common cause of that symptom is a shorted horizontal output transistor, caused by a cracked solder joint on a small coil connected to that transistor's base. When this happens, the main B+ supply is shorted to ground so the power supply squeels. Every once in a while I also see the horizontal output transistor shorted due to a shorted flyback (high voltage) transformer. A good tech will replace the horizontal output transistor, resolder the coil and drive transformer, test the flyback (replacing it if necessary) and your set will be back to perfect.
When the horizontal output (2SC4927) is shorted it means one of 2 things is wrong - the horizontal drive transformer has cracked solder joints or the flyback transformer is shorted inside. If the solder joints on the horizontal drive transformer (the small grey transformer connected to the base of the horizontal output transistor) are cracked then the set will play for a little while and then the parts you just replaced will again be destroyed. ALWAYS resolder the driver transformer when replacing the parts you mentioned! When I replace the parts you mention and I do not see any obvious cracks on the driver transformer then I unsolder the B+ pin of the flyback (labeled 135, for 135 volts) and put a 60 to 100 watt lightbulb (drop-light) in series with the flyback. This means that the 135 volts B+ goes through the lightbulb and then into the flyback, so the lightbulb acts as a current limiter to protect the horizontal output. When you turn the set on the bulb should glow no more than about half bright and you should hear the high voltage come up, but you should not see a picture. If you turn the set on and the bulb glows as bright as if it was plugged into the wall then you can bet that flyback is shorted and must be replaced.
The horizontal output transitor is always connected to the primary winding of the flyback transformer (via collector) and also to the horizontal deflection coil via an electrolytic capacitor.
The most likely suspect for damaging the transistor is the fylback transformer. In some countries there are electronic stores that test flyback transformer by winding a few turns on the ferrite core and applying a test voltage. This test will only test the secondary.
The primary winding is difficult to test for turn to turn short because the resistance is quite low and you do not know the 'good' resistance.