5U4G U52 OSRAM 10E/373 RAF AIR MINISTRY U52 BLACK BASE WARTIME PRODUCTION
Here we have a single 5U4G, a military specification U52 DIRECTLY HEATED TAPE FILAMENT rectifier manufactured by Marconi Osram at their Hammersmith Brook Green factory which carries the etched elliptical wartime cartouche.
This valve shows excellent bright getter and has the inverted getter pan situated down by the glass pinch, it tests as EXCELLENT using my Avo VCM163 valve tester. This exquisite device is fitted with the grey base/envelope shrunk sleeve, fitted by Air Ministry stores to devices to be utilised in airborne applications, consequently the trademark rounded black low loss micanol base is tight to the envelope.
Device test data: Ia = 120.0mA for both diode sections.
Device specification 120mA delivery for both diode sections. So you can see we have 100% emission from this venerable beauty.