in my Tecktronics TDS100c model internal SMPS is from Emerson , it has been damaged , its TOP244yn IC is gone bad[smoke is there near] , so i replaced with new one , after that out put is coming 3.3v but it will on at 2sec and off at 2sec and repeating , what should i change .see the attached smps photo
The usual recommendation is to replace any electrolytic capacitor which shows signs of bulging or leaking. In addition, about half-way up the left side of your pic (just above the big 450V cap), the solder joints of the legs of the component clamped to the heatsink look dodgy.
You should check the Mosfet which is in serial to the transformator. Also check the values of coils at transformator if you have LCR meter looking for a short circuit between coils or bad Q value. You also must check the secondary diodes and power supply for PWM IC, sometimes it takes power from rectified voltage auxiliar coil at transformator.