When opening the back cover of the TV set, I found two bad filter capacitors 470uf/25 volts. Replaced them but nothing changed. The screen remained black and the sound still there. I checked everything in the power supply primary side and all checked to be good. I started to check the secondary output area and all checked ok but one transistor was bad- A1013. It was shorted on all the pins. This transistor was connected to a diode then it goes directly to the vertical deflection IC LA7833.
29 volts was coming out from the SMPS but only 19 volts going to the vertical IC through this transistor. I took the faulty transistor out and replaced it with the same exact part number and the screen came on but only half screen.
I rechecked the voltages but it was the same i.e. 29 volts came from the power supply but only 19 volts coming out of the transistor and going to the sixth leg of the vertical IC LA7833 which is the power input (Vcc) of the IC. I took the new transistor out (where I have just replaced it) and it checked ok but it was acting really strange. Then I thought of something. I looked in my old electronics chunk pile and found a transistor with the same part number (A1013). I did not know that I could locate such a same part number in the store.
I replaced it with the transistor I found from the junk equipment and guess what? The TV had full screen with nice colours. And I thought to myself, this transistor is brand new and it was defective. Wow, I was really shocked but I was happy at the same time that this TV set worked after a very long confusing hours.
I talked to the guy who sold me this transistor and he told me that the part that I bought was made in China and sometimes a new China made parts could be defective even though it was new.
Anyway, the TV set worked perfectly nice and I was happy about it.