4 B7971 tubes with built tested "four letter" clock PCB Discuss 4 B7971 tubes with built tested "four letter" clock PCB https://www.tubeclockdb.com/index.php/on-ebay/208-4-b7971-tubes-with-built-tested-qfour-letterq-clock-pcb Thu, 28 Mar 2024 23:58:11 +0000 JComments