A Jennings Univox J5 from early 1953
In progress, Jan. 2025
J5 serial number 664. J5s did not have an illuminated logo (first fitted to the J6).
On this page, a brief overview of the only Univox J5 currently known - a superb thing - serial number 664 from early 1953, the 65th made. An overview of the advertising relating to the model, Tom's first major production, can be found on this page.
Four circuit diagrams survive for the J5, drawn out in final form in the autumn of 1954 and saved from oblivion in 1969 by Rodney Angell. It may be possible to give a more detailed account of these at some point.
In terms of date codes: two of the original BEC electrolytic filter capacitors in the amplifier section have "SEP 1952" and "OCT 1952"; the gasket of the Plessey speaker is stamped "7153", which is likely to mean the 7th January 1953; and the chassis has a small metal strip inscribed "No. I 153", perhaps indicating that it was the first one fabricated in January 1953 - it certainly does not mean the 153rd. Final assembly evidently took place some weeks later as the volume potentiometer in the keyboard section (console) is dated "BA" = February 1953.
Long in Australia, serial number 664 may have been exported there from new.
General views
The inside of the case, the keyboard stowed beneath the amplifier. As can be seen, the J5 had tabs to select the speed of the vibrato and the three ranges (Low, Medium, High), not rotary controls. Those came later with the J6, J7, and J10.
Detail of the "Univox" plate and geometric basketweave vinyl.
Serial number plate on the rear of the keyboard section. The sequence is likely to have begun at 600.
Oval Jennings emblem on top of the case.
Amplifier
Interior of main case.
Mains transformer renewed in the 1960s. The two output valves are currently 6M5s, a good substitute for the original EL41s.
Rear of the assembly.
Goodmans output transformer.
Inscribed strip.
Keyboard
The keys numbered at rear.
Resistor array (tone filters).
Key assembly.
Keyboard (console) electronics, in the centre foreground the Pulse Generator circuit for the effects controlled by the tabs. The octal valves are: three 6SN7s, and one 6SL7 (lower right).
Volume (swell) potentiometer, date code "BA" = February 1953.
Speaker
10" Plessey speaker.
Date code on the gasket, 7th January 1953.