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 Changhong color TV CHD-2B CHD25800
Turn the phone, the boot has a similar line frequency scream, the screen does not light.
Observe the waveform of the collector tube of the boot tube with an oscilloscope, similar to the waveform of the S capacitor failure (previously repaired by Changhong HD), unplug the deflection, observe the waveform of the collector of the tube is still disordered, and eliminate the S capacitor and deflection problem.
Do not understand, online measurement S capacitor is normal, there is no problem with the feedback ceramic capacitor. . Suspected that there is a problem with the high voltage package, but with the 555 tester, the high voltage package has no AC short circuit.
Online search, all said to be a deflection problem, but I pulled out the deflection, the scream still exists, doubts, and dubiously removed the deflection. . .
Repairing the deflection, handy, and soon found the problem. . .
Summary: This fault deflection damage is reasonably unplugged, the collector electrode waveform should be the peak drop, the reverse stroke is increased, there should be no disorder and screams, but the case is exceptional, it is endless.