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.