FYI, and for more than a decade, a popular PS in the ARRL Hdbk, say 2000 edition, a 28 V @ 10 A has a goof. The crowbar ckt as shown does not work. The MC3423P OVP IC is biased from a 12 V Zener via a 4.7 k series R. Trying to fire an SCR, the Zener falls out and the circuit fails. Change the series R to the Zener to 820 ohm. All is then bliss.
Nope, so it is not part of the errata list. So the contact for errata items by the way is:sford@arrl.com
Goes to show how few hams actually try to build the construction projects described in the Handbook. After a whole decade, no-one had called attention to the error.