Another Tektronix 2235 troubleshooting.

please tell me what should i do now . . . . . .
How long will it take you to figure out that the odor /smoke will tie into a component . . . and it will probably / usually show it.
Drop the cover and concentrate on the center to right rear and center to right side quadrant, as that is the heaviest concentration of most likely parts.

 

That model oscilloscope has the nastiest most convoluted complex switching power supply circuitry I have worked on.

Use visual/nose detection of components burned and relate to schematic.

Barely remember a small electrolytic capacitor at the edge of the printed circuit board failed often in several units. Other times also open electrolytic capacitors needed replacement in the same area. Typical symptom was ~1Hz repeated attempts to turn on.
Once I had to give up on one of a dozen I repaired, all with power supply problems.. Could not find the failure
That same day I gave my Tektronix to a needy person and never bought that brand again, no matter how famous they were. My wimpy Hitachis have never failed.