Pair of NOS 6900 MU Retested (Bendix type) Vacuum Tube
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Pair of NOS 6900 MU Retested (Bendix type) Vacuum Tube Picture(s) and Description:
Normal 0 false false false EN-US X-NONE X-NONE I received a large group of tubes from a US Vacuum Tube Manufacturer for the purpose of testing, evaluating, and selling. Up for auction you will find a Pair of NOS MU 6900 Retested (Bendix type) Pulse Vacuum Tube. The comparative testing standard for this MU 6900 tube was to a Bendix 6900. However, the original Bendix 6900 is not an Audio Tube. It was specifically designed for Pulse applications in missiles, aircraft, and other military and industrial installations. The original pulse testing used to evaluate these tubes will not tell you anything about how they would perform as an audio tube. The 5687 has for decades been thought of as an audio tube by the audiophile community. There are very close electrical similarities, yet very distinct differences in physical construction, when you compare the 5687 to the 6900. Because of the nature of the 6900 due to its physical construction, the warm up time required to the point of stability, is longer than that of the 5687, and extremely longer than the popular dual triode audio tube: i.e. 12AX7. However, these 6900 pulse tubes up for auction have been tested as if they were a 5687. Each tube has been tested on a TV-7A/U (minimum passing value is 38) and a TV-2C/U (minimum passing value is 54%) with a warm up time in excess of 5 minutes to ensure the point of stability. The results are documented on the tube box. If you are interested in learning more about the 6900 we would recommend reading the following: "How to Get the Most Out of Vacuum Tubes" by Robert Tomer and/or "A Brief History of Bendix Red Bank" by Charles Hansen. If you have any questions, please contact the seller before bidding.