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Armstrong 127M

From valves
From valves
 The styling is quite modern - for the 1960s - and once again there are no station names. The lack of scale illumination is surprising.  There's an unused valve socket - apparently a stereo decoder can be plugged in here.  There's space for a second output valve - for the push-pull version.  This set has a single-ended ECL86 output.

A mono AM/FM receiver from the late 1960s.  The design, and styling, is from the Armstrong 200 range but the output stage is a single-ended  ECL86 (triode pentode).   The Mullard valve codes make is easy to figure out what each of the valves do in sets like this.  'E' means 6.3V heater, 'C' - triode, 'L' - output pentode.  The other valves are ECC85 - double triode, EF80 - small signal pentode, EBF89 - diode pentode, and ECH81 - triode hexode (frequency changer).  There's no rectifier valve as it uses a pair of silicon diodes to form a voltage doubling PSU.

Some internal rust but otherwise in good shape.  This set had been overhauled by someone else not too far back.  A couple of electrolytic caps had been replaced and I had to replace a few more.   This is now my workshop radio, and it works well and sounds good.

According to the diodes used in the voltage doubler of the 222 amplifier were RS240AF.  I've seen an example with the more common Mullard BY114, perhaps other types were used too.  See for diode specifications.  The BY114 has a max reverse voltage of 450V and max current of 450mA - a useful reminder of how even in the 1960s silicon was a formidable replacement for valves.