Made in USA NOS milspec 6X4WA Tung Sol. Rare and in demand as one of the very best sounding 6X4 or EZ90. Limited availability. 3 or 4 or 5/59 so real vintage almost 60 years old. Known to be recommended by famous tube tuners for upgrading any 6X4. Only the GEC 6X4 seems to better the Tung Sol - at a price! Please be aware the print on the tube is fading so not 100%. Tested on the Amplitrex AT1000 with NOS test results. Black plates D getter.
NOS Russian tube rectifier 5U4C. Equivalents 5Z4GT. This vintage Russian 5U4C (5Ц4С in Cyrillic script) rectifier is a 5Z4 equivalent. This slow-rise, indirectly-heated rectifier should be considered an upgrade for a 5Y3 tube in most circuits, and will drop slightly less voltage. It has gray plates and a bottom dish getter. The silver print on the base has the OTK inspection stamp. Made XI-75.
Russian NOS 72's Reflector 6Z4 equivalent of a 6X4 EZ90 but different pinout. Cost effective upgrade rewiring one wire from pin 6 to 7. Black plates. Chinese 6Z4 is direct replacement. 5000 hours longlife molybdeen pins cleaned with Deoxit.