SV3 Radio Magnadyne Radio

Posted on Feb 5, 2014

Most models produced in the 30s rely on very similar circuits; in particular the RF section of most sets relies on the same LW-MW-SW scheme while the differences between different sets are based on the presence or absence of the variable selectivity control, on more or less sophisticated tone controls and on the output stage. Some of these sets relied on European

SV3 Radio Magnadyne Radio
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tubes (typically AK1, AF2, E444, E443H, 1561) or on American ones like 6A7, 6D6, 75, 42 and 80; some sets, like the SV13, used a mix of European and American tubes (AK2, 78, 75, 42 and 80). The SV3 was an high end model based on the European set and was endowed with a variable selectivity control mechanically coupled with the tone control. The unit described in this note was almost untouched; the only substitutions concerned one electrolytic capacitor and the power cord. All other components were the original ones and also the tubes were original and characterized by the lead seal that testified the payment of Italian taxes; they were also perfectly efficient, with the exception of the E443H whose filament was interrupted. Because of the high quality of all components it was expected that only a very limited number of substitutions would have been necessary; this was, in fact, the case but some other aspects called for a substantial amount of work. This note describes the points that, according to my experience, require more attention. To shorten as much as possible the length of the note, these points will be treated as separate items of a list. 1) Restoring the wiring. Differently from many other receivers produced in the same years, most of the SV3 wiring was based on rubber coated wires. Some wires were of the stranded type, others were solid and, to complete the picture, several colors were present for both types:...

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