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 |
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