Capacitor Size

Are you asking about power supply aluminum electrolytic caps or film capacitors???

Your technician was on the level. Its a general rule of thumb that electrolytic capacitors (the kind found in power supplies) decrease in size in newer versions. It was that way in the 1970s and is still true today.

yep, Atmasphere is correct. The new caps for a given microfarad value and voltage are usuall considerably smaller than caps from 10 years ago let alone older caps out of 1970s or 1980s vintage gear. sounds like your repair guy is being honest with you.

The smaller value Electrolytic capacitors like 10KuF to 25kuF are smaller than caps from 20 to 30 years ago. The big 50000uF/125V,76000uF/100V,51000uF/160V caps cannot be made smaller than 3 inches in diameter and 5.9 inches long.
Even in the 1980s and 1990s these caps were same size as today.

The reason caps had been able to shrink in size is do in part to over etching the aluminum foil to increase its surface area. When you do that, less foil is needed and the body of the cap can shrink. Up until recently, when compared to their larger cap brethren, the smaller etched aluminum cap did not sound as good. I tried this experiment with the same manufacturers cap, just different case size. It was missing the relaxed quality of the larger cap. Note that both caps had been broken in. Although caps now still vary sonically from manufacturer to manufacturer, I believe the days of over etching the aluminum are over especially if the cap is designed for audio applications. You will note that caps designed for audio applications are usually a bit larger in case size for the same value.