This month's curious offering is the PEN383 from Mazda. Our example comes from a Murphy D70RG radio. This radio is one of the first of a generation of the awful 'live chassis AC/DC sets. That is to say, receivers operating without an isolating mains transformer. This was particularly nasty if you hooked up to the 'gram' input, rendering your record player live! The Pen383 is a beam tetrode audio output valve on a Mazda Octal base that was designed for 200mA series heater connection.. The Pen383 could produce just under three Watts of audio (single ended) and was the 'series wired' near equivalent of the PEN45. It has a slightly larger than normal envelope for this sort of valve, measuring 54mm in diameter. Also of note is the internal graphite coating which prevents us from getting a good look at the insides. Thanks to Mazda wiring the heater to pins 1 and 8 instead of the more usual pins 2 and 7, it has no direct equivalents. In summary, a bit of an odd ball.
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