double diode - pentode UBL21 - (NIB)
UBL21 is a double diode - output pentode. The sensibility of the pentode system is very high. It is suitable for usage in different types of amplifiers. Indirectly heated cathode is common for both of the systems. UBL 21 was also a part of many smaller radio receivers from Tesla factory ( 305U, 306U, 307U a 308U Talisman, T254, Rytmus, 504U-II Pionier, 401U Accord, 402U, 405U Standard a others). New old stock tubes, new in box. Tubes are packed in vintage Tesla boxes. Tested on BM215A.
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