Description

2 x 12AT7 Mullard Tubes Made in Gt. Britain O-Getter Codes B4L3 & B4K5 = 1964 Lettering may be smudged/missing Tested on Enhanced Triplett E3444 Laboratory Tester by Paul Hart of Roswell Ga. 5700/5600 micromhos @ 10.7 & 10.6 mA 5300/5350 micromhos @ 10.0 & 9.6 mA Bogey(100% or New) = 5500/5500 micromhos @ 11.0/11.0 mA +/- 10% The measurements in this listing were taken on a Triplett 3444 modified to test the tube as an amplifier in accordance with RMA/EIA specifications, utilized by all US and most foreign tube manufacturers. This tester applies test conditions for this tube as shown below (including the precise filament voltage) and then measures transconductance (gm) in accordance with the engineering definition of gm. Tubes may also be operated under the test conditions for extended periods to be sure that it is stable. A tube must be tested in this manner to compare its test results with the manufacturer’s original intent or with other tubes of the same type. Most tube testers do not apply the test conditions required or conduct a valid gm test. For more details on the test and our test equipment, please contact us. The test conditions for this listing are __ 250 _Volts plate, __ 250 _Volts screen, ___ -2.0 ___Volts bias or Cathode resistance * What were your tubes tested at? I do combine shipping