EL84 Mullard, Cossor label, earliest production 1955 v27

85,00

Highlights

    • First Mullard series rX1
    • 1955 !
    • closed elliptical getter
    • Excellent sonics

1 in stock

Description

Here is an ultra rare EL84 (6BQ5) tube made in 1955 by Mullard, Blackburn

Detailed description

This Mullard rX1 EL84 with closed elliptical getter and welded plate is from the Blackburn production site.The EL84 is a pentode. The old Mullard production from the past century is recognised as the ‘crème de la crème”. This EL84 form the very first production series delivers superior sonics. I refer to the many reviews on the web

The tube bears the date code rX1 B 5J. This means that the tube is made in October 1955 !

The Mullard EL84 closed elliptical getter rX1 series is considered by many as one of the best sounding EL84 tube; a lot better than todays production!

 The tube has been thoroughly tested and has excellent electrical values (note test results below). Very strong tube! A rare opportunity indeed!

Mullard

Mullard Limited was a British manufacturer of electronic components. In 1923 Mullard formed a partnership with the Dutch manufacturer Philips. Mullard finally sold all its shares to Philips in 1927. In 1928 the company introduced the first pentode valve to the British market. In the late 1930s Philips opened a plant in Blackburn. By the end of the war, nearly 3,000 workers were employed. In 1962 over 6,200 were employed and Mullard described the Blackburn works as “the largest valve manufacturing plant in Europe”. Mullard opened a new manufacturing plant in Mitcham, Surrey in 1929. A second building was added in 1936. Both buildings were very similar to those at Philips’ headquarters in Eindhoven, Netherlands. Mitcham was also home to the Mullard Application Laboratory.

Test method

Mutual transconductance, plate current, gas and shorts tested with: AVO CT-160 (Dutch army tester), Utracer3+, Philips 1532, RFT stabilised power supply and 2x Keithley 2700. Test conditions: Anode 250V, Screen 250V, Grid -7.3V, Filament 6.3V, Rated Ia = 48mA, Gm = 11.3 mA/V. AVO Valve Data Manual 23rd edition 1981 Before testing they were burned in for 48 hours.

Test results*

The measurement data below show that the tubes test NOS and are matched. 

Valve 

V27

Ia (plate current):

Transconductance (Gm):

Gas test, Shorts test:

 46  mA

10,5  mA/V

OK

NOS

NOS

 

 

Summarized description

Tube type 6BQ5   (EL84)
Quantity of Tubes One
Brand Cossor
Manufactured by Mullard
Date code rX1 B 5J  (1955)
Plate Construction round hole in plate
Getter Construction closed elliptical getter (see pictures)
Print Condition Excellent; see pictures
Box included Generic box
Equivalent tubes:  CV2975 6BQ5 7189 E84L EL84
General test results  NOS 
Please study photos carefully; what you see is what you get! Ask any questions before bidding.

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