5Y3

Full-Wave Vacuum Rectifier Diode, engineered to convert alternating current into stable direct current. Operating with a 5.0V heater, it handles a maximum DC output current of 125mA, making it a ubiquitous industry standard for B+ power supplies in vintage tabletop tube radios and electronic test instruments, housed in a standard large 8-pin Octal-style base glass envelope (T-9 bulb).