Old Macintosh Power supply chirping
Look for a current sensing resistor or fuse and measure it the look for DC OK or OVP protection signal.  Monitor main Voltage on power-up and look for a spike or any sign of voltage on the ACDC  converter. It could be a bad choke, diode ,transistor etc.
I recall Apple big screens were notorious for bad solder joints on heavy flyback transformers causing PTH via fatigue.  (invisible microcracks)  The chirp tells me the flyback switcher was working then failed due to overvoltage. (&gt; 25kV?)
Then retries after settling time.