I wouldn't call the UC384x "vintage"; they are still in production today. Likewise, the TL494/KA7500 was very common in PC PSUs and is still in production too --- perhaps you could analyse its die circuitry for comparison.

For schematics of power supplies using this UC3842 chip, see this site, near the bottom of the page.

Before looking at the URL I guessed it would be that site. The author is also on YouTube under the name DiodeGoneWild, and not surprisingly posts videos about SMPS electronics too.