M-OV's first indirectly-heated HT rectifiers were the MU12 and MU14. These were in fact the same valve but only a minority of each production batch were good enough to withstand the full rating when tested. These few were labelled MU14 but the 'also-rans' (initially the large majority) were labelled MU12 and sold against a reduced specification (350 V).The Marconi paper label.Face view of one anode.The classic envelope is 45 mm in diameter and, excluding the B4 base pins, is 102 mm tall.References: Data-sheet. Type MU14 was first introduced in 1933. See also 1933 adverts. |