Model: Konka color TV T21SA267
Symptom: The power-on indicator is on, but there's no sound and no picture. With the remote control, the TV doesn’t respond during the second boot. B+110V is normal, and the 76931 power supply is also normal. However, the filament isn't lighting up, and the voltages at pins 8, 11, 19, and 55 of the 76931 indicate that the TV is on. Testing the primary side, the 110V power supply is present, but when testing the C pin, there’s no voltage. Careful observation shows that the push tube and transformer are intact, but the transformer is clearly damaged.
Since the push transformer has no 110V power supply, I had to find a replacement. After finding a suitable substitute and soldering it onto the board, I turned the TV on again. There was a loud "crack" sound, and the screen saver appeared briefly, which made me think the issue was fixed. However, after connecting the video signal, there was still no image. Pressing the menu button, I noticed that the left part of the menu was blocked by a horizontal blanking line. Switching to TV mode, a black band was visible on the left side of the screen.
This kind of issue usually points to a problem with the line pulse signal. I’ve seen similar faults before, and in those cases, the secondary coil of the push transformer was reversed. In this case, the primary coil's head and tail were also reversed, leading to an abnormal AFC signal being sent to the 76311 chip’s 44th pin. This caused the AV input to have no image and the black band on the left side of the screen.
After correcting the polarity of the push transformer, the TV worked normally. This is a common fault in Konka TVs, so I always remind beginners to double-check the direction of the push transformer when replacing it. A small mistake here can lead to significant issues later on.
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