Interest in Nixie tube clocks has gained momentum in recent years with modern designs paired with new old stock (NOS) tubes from the ex Soviet block or Mullard – Philips nearer home. You may be interested in the history of the first Nixie digital clocks or at least the first available in the United Kingdom back in the nineteen sixties…
Darang Ltd manufactured digital systems including logic modules, timers and clocks in the nineteen sixties. Their factory was based in Hackbridge in England not far from Mullard’s vacuum tube and transistor factory in Mitcham, Surrey.
The black cased Digicron model below went on sale in 1965 and offered both 12h and 24h digital display. Consuming 25 watts the clock used the 50Hz mains supply as a frequency source – common for most synchronous electro-mechanical clocks of the period. Originally priced at £90, this was an expensive clock and provided a space-age style for the time. There was also a six digit version made to show seconds that cost a little more. The design utilised Mullard ZM series nixie tubes for the display along with GTE trigger tubes for the decade counters. Like nixies, trigger tubes also used neon gas to strike as tetrodes having an anode, auxiliary cathode, trigger, and cathode. With suitable voltages, two red glows are maintained in the tube, one between the anode and auxiliary cathode and the other between the trigger and cathode. Trigger tubes could suffer from reliability problems though and any mains interference could add the odd minute or hour to an otherwise accurate display.
Darang Black Perspex Nixie Clock
This photo was taken from an advert that appeared in Practical Electronics October 1965. The clock also featured in the media at the time.
Later in 1967, Darang developed a new Digicron version aimed at the industrial market. This digital clock still used nixie display tubes and the decade counters were replaced by semiconductor logic driven from internal time source offering much better stability. A larger 30mm nixie tube was used for hours and minutes along with a 15mm for the seconds.
Darang Digicron Nixie Clock
Various models were produced including oven controlled crystal oscillator time sources along with date and day indicators. Claimed accuracy of the oven controlled time sources was two parts in a million. Power consumption increased to 35 watts.
A brochure with details of the Six-Seventy clock is available below.
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