Can you replace bad ob2269(SMPS not clicking any longer and chip has
about 1 V on pin 3(VIN) although in front of it there is 310V) with
sg6841 or ld7552 or some other without modifying circuit around
it(except for the sw. frequency setting resistor)

What should one check Zfb,Zcs first, or missing leading edge blanking
block and one diode after fb input inside 0b2289?
(real ob2269 circuit has different component values and in addition
resistor divider at MOS gate and one more diode+capacitor in front of
VDD)
http://www.dianyuan.com/bbs/u/36/1135072817.pdf
http://www.leadtrend.com.tw/pdf/LD7552-DS-00.pdf
http://pdf1.alldatasheet.com/datashe...TC/SG6841.html