TV WORKS FINE. BUT WHEN YOU ADVANCE THE VOLUME, PICTURE JERKS AND GOES INSTABLE

     This is a common fault to most of the picture tube based TVs.  When we advance the sound, the picture will jump, jerk, and will go instable.  I’ve experienced this fault for more times in my 40 years of continuous service work. I’ve checked and replaced most of the components in audio section, but went in vein.  The fault is very simple.  No multimeter test will help you to vet to rectify this problem.

The sets experience this type of fault will have a choke coil fitted in series with the secondary power supply point, which supplies voltage to Line Output Transformer. This voltage is supplied from the SMPS section of the power supply system.  Normally this voltage will be between 95 to 135VDC.  After rectifying this voltage. From the SMPS transformer by a diode. There will be a smoothing capacitor.  Usually this will be 160uF 250 V or so.  After that, there will be a coil. [Peaking coil], fitted in series with this supply.  After this peaking coil, an other capacitor will also be there.  It will be usually have ether value 22uF 250VDC. Normally this capacitor will be the cause to this problem. The values of these capacitors may vary according to sets.  Check these capacitors for damage.  Replace both of them with same capacitance value and voltage.  No other work should be done for this fault.