Osram

  • Marconi-Osram Valve Co

    • 1919 Marconi-Osram Valve Company formed as company owned jointly by GEC and Marconi's Wireless Telegraph Co; it took over GEC's valve factory.
    • 1920 Name of company changed to M-O Valve Co[.
    • 1920 Jan. Physical and Optical Societies Exhibition. Exhibited wireless telegraphy.
    • 1927 Recorded as being a subsidiary of GEC
    • 1929 Gramophone Co acquired Marconiphone Co as well as Marconi's share in M-O Valve
    • Continued to supply valves to Marconi.
    • 1956 GEC purchased EMI's share in the M-O Valve company.
    • 1969 Formation of GEC Electronic Tubes to bring together M-O Valve and English Electric Valve Co, a company which would have half of UK valve production, the largest specialised valve manufacturer outside USA
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OSRAM BLACK BASE KT61 FROM NOV 1953

On offer today we have a beautiful Osram device. It tests as 100% emission as you can see from the attached test data label courtesy of our AVO VCM163. The envelope carries the etched ellipse cartouche and the black micanol base is tight to the envelope and shows clean uncorroded pins - a simply super device.
¥401.94

BRIMAR 5Z3 BROWN BASE MANUFACTURED BY OSRAM JAN 1956

Well, what a special device, essentially a U52 mounted on a UX4 base, this is a superb valve indeed. Badged in black base print as a Brimar but from construction and faint cartouche is an Osram manufactured device this is scarce and desirable too. Showing perfect emission on test, will you give it a home?

MARCONI OSRAM 5U4G MILITARY U52 BROWN BASE 1955 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 both white inked print and 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 carries good white print, the classic U52 envelope shape and the trademark rounded brown low loss micanol base - simply super. The pobverse of the vale carries a large MArconi blue and white decal. 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.
¥1,786.40

MARCONI OSRAM CV1071 MILITARY U52 BROWN BASE 1955 PRODUCTION

Here we have a single CV1071, a military specification U52 DIRECTLY HEATED TAPE FILAMENT rectifier manufactured by Marconi Osram at their Hammersmith Brook Green factory and carrying the cartouche code for August 1955. This valve shows excellent bright getter and has the inverted getter pan situated down by the glass pinch, the valve base is very slightly loose on the envelope, however, more importantly it tests as EXCELLENT using my Avo VCM163 valve tester. This exquisite device carries good white print, the classic U52 envelope shape and the trademark rounded brown low loss micanol base - simply super. The pobverse of the vale carries a large MArconi blue and white decal. 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.
¥1,786.40

OSRAM BROWN BASE KT61 FROM FEB 1957

On offer today we have a beautiful Osram device. It tests as 100% emission as you can see from the attached test data label courtesy of our AVO VCM163. The envelope carries the etched ellipse cartouche and the brown micanol base is tight to the envelope and shows clean uncorroded pins - a simply super device.
¥401.94

OSRAM BROWN BASE KT61 FROM FEB 1958

On offer today we have a beautiful Osram device. It tests as 100% emission as you can see from the attached test data label courtesy of our AVO VCM163. The envelope carries the etched ellipse cartouche and the brown micanol base is tight to the envelope and shows clean uncorroded pins - a simply super device.
¥401.94

OSRAM FAT BOY KT66 VT75 WARTIME ISSUE GREY GLASS

The British Marconi-Osram GEC Valve Company of England introduced in 1938 the legendary KT66, K.T standing for kinkless tetrode. This designation was given as when the performance of the valve is measured from it's output curve it was found to be linear - hence it's great sound. The KT66s superlative sonic performance found audio fame in the Q.U.A.D II amplifier in the field of hi-fi and in 1965 Jim Marshall used the KT66 in the JTM 45 guitar amp to power those famous biting solo's to a crescendo in Eric Clapton's band!! Hence the KT66 joined the rock and roll valve legend in the first position where it has been ever since. The performance of the MOV originals is all due to the heavy grade glass and rigid mica spacers with stiff grid support specified by MOV engineers to eliminate microphonics and provide longevity of performance. Many replicas of this valve have been made over the years, mainly in China but these replicas don't 'cut the mustard' in comparison to the original GEC MOV devices in terms of sound, longevity and visual aesthetics. The problem is not just locating vintage devices but getting good ones which have been fully tested using an AVO VCM to determine stability, microphonics, cathode heater insulation hot & cold, internal shorts, anode current and mutual conductance. For this you need expertise and the requisite Valve Characteristic Meter - hard to find and jealously coveted these days - and so they should be as they cost the price of an average semi back in the 1950's The device offered here today is AVO VCM163 tested and as good as you can get. Its a GREY glass, black low loss micanol based unit from wartime production. The base is tight to the envelope with no sign of re-fixing. The markings on the front are in etched cartouche and show KT66 Osram and the rear of the envelope carries a perfect Osram ellipsoid yellow and blue decal. Tested using an Avo specification for 100% emission of anode current, Ia =63 mA; mutual conductance gm = 6.3 mA/V @ At Va = 250V Vg = -15V the results obtained were:- Ia = 95 mA. gm = 8.0 mA/V.
¥1,741.74