Thorn Beta 2

Lantern acquired in April 2012.

Little is known of this Beta 2's history, except that it spent much of its life out of use residing in a shed in Braintree, Essex. When the shed was subsequently cleared out in 2012, the lantern passed on to me. Along with its later variant, the Beta 2 was a common lantern on the streets of Derby for many years until the Street Lighting PFI significantly reduced its numbers; however, the lantern continues to be seen on some roads that have avoided replacement, and can also be seen in reasonable numbers throughout the wider county of Derbyshire.


Having seen little outdoor use, the lantern was in excellent condition upon entering the collection. The only cleaning work required was to remove some superficial dirt marks from the canopy and bowl. This variant of the Beta 2 can be identified by the offset NEMA photocell; later versions saw the NEMA socket relocated to a more central position on the canopy in order to match the design of sister lantern, the extremely popular Beta 5.


These lanterns often came with their canopies painted light grey, though in many cases, the paint wore off over time. Later versions did away with painted canopies and simply opted for unpainted aluminium canopies. Having been out of use for many years, this lantern is something of a time capsule from another era - a Royce Thompson P5 thermal photocell can be seen fitted to the NEMA socket. By 2012, thermal photocells were very much a dying breed for street lighting use on account of their high power consumption and issues with sensor drift in comparison to all-electronic photocells.


Removing the photocell reveals that it was manufactured in February 1990.


The refractor prisms moulded into the lantern's bowl do little to mask the three-quarter length reflector and gear tray.


Removing the bowl reveals a rather worn OSRAM 'SuperSOX' lamp.


The date code on the lamp (VA) suggests a manufacture date of January 1988.


From 1984 until 1987, Thorn included the EMI suffix in its branding, following the merger of the two companies in 1979.


The inside of the lantern was virtually spotless. Curiously, the supply cable clamp was missing.


The standard arrangement of a ballast, ignitor and capacitor was employed to run the lamp. Interestingly, the gear tray in this lantern was always relatively flat; this contrasts with contemporary Beta 5 lanterns, as the gear trays in these hadn't been updated from their initial inception as the AEI Amber Minor, which was designed to accommodate much larger gear than what was being fitted by the 1980s. As the Beta 2 was also launched in the same decade, the gear tray was designed with smaller gear components in mind from the start. (The Beta 2 name had lain dormant for many years - the previous lantern to carry this name was a stylish (albeit relatively short-lived) twin 40 W fluorescent fitting.


A very faint date stamp on the capacitor informs us that it was manufactured in November 1985, suggesting that the lantern would have been assembled in 1986.


The lantern was attached to a wall bracket on Sunday, 27th May 2018.

Using the dependable Woolworths' plug that had been connected to the lantern prior to acquisition, the supply was switched on and the internal GE-made 55 W SOX lamp emitted the distinctive blood-red glow that is so unique to a low pressure sodium lamp.


Within a few minutes, the lamp had warmed up, and the lantern was operating at full brightness.


Lamp switch-on video:

Testing with my energy monitoring device revealed the following results.

Test Voltage (V) Current being drawn at full power (A) Measured wattage (W) Apparent Power (VA) Frequency (Hz) Power Factor True Power (W) Difference to rated wattage Percentage Difference
243.6 0.56 76 136 49.9 0.56 76.39 21.39 38.90%

Phosco P111 | Philips 'Libra' 2565




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