Changhong color TV CHD25800 boot has a similar line frequency scream sound screen does not shine fault repair - android - Phones Developers

Single chip microcomputer STM32L151CCU6
Test - lowercase jpg
Mobile phone crystal 3.2*2.5mm 3225 26M (26.000MHZ) 7.5PF 10PPM 20PPM 30PPM
Kaixin micro test
Test probe P100-M3

Maintenance of Changhong color TV CHD-2B CHD25800
When turning on the TV, there is a similar line frequency noise, and the screen does not light up. I used an oscilloscope to observe the waveform at the collector of the boot tube, which resembled that of a faulty S capacitor (previously repaired by Changhong HD). After unplugging the deflection coil, the waveform remained distorted, so I ruled out the S capacitor and deflection coil as the issue.
Online research suggested it was likely a deflection problem, but even after removing the deflection coil, the noise persisted. This made me doubt the initial assumption. I continued testing and eventually found the real cause.
The problem turned out to be in the deflection coil itself. Normally, the collector waveform should show a peak drop with a smooth reverse stroke, but in this case, the waveform was chaotic and caused a loud noise. The root cause was a short circuit due to corrosion from glue inside the component.
A row tube collector waveform.jpg
B problem deflection.jpg
C where the problem occurs, due to the corrosion of the glue caused by short circuit phenomenon.jpg
D failure location.jpg
E fix.jpg
F fix. .jpg

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