Here we have a single U52 DIRECTLY HEATED TAPE FILAMENT rectifier manufactured by Osram at their Hammersmith UK factory. This device is AIr Ministry production as evinced by the grey base-envelope oversleeve. These were applied by the AIr Ministry stores in 1958 as a palliative measure to prevent base loosening. A little judicious work with a razor blade can remove the sleeve and in all probability the envelope will be tight to the base, but, I always leave these on as they are a sign of provenence andpart of these beautiful devices history.
This device carries the white cartouche CV575 markings in perfect white print displaying the date code HE which equates to May 1955.
Highly sought after not just for the impressive current delivery performance but for it's extreme musicality and deep bass extension in hifi applications this is a nice lot indeed. Even more so as it's in the delicious bulbous envelope presentatiion which not only enhances sound quality but looks wonderful. . No wonder all the high end magazines rave about these beauties.
This valve shows excellent bright getter and has the inverted cup getter pan situated down by the glass pinch, the valve base is tight to the envelope but there is some loose valve cement caught within the base , however, more importantly it tests as EXCELLENT using my Avo VCM163 valve tester. This exquisite device has good sharp getter, the classic U52 envelope shape and the trademark rounded brown low loss micanol base - simply super.
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