Thorn Beta 5

Lantern acquired in May 2019.

By the 1990s, the majority of Beta 5s sold were of the side-entry variety; however, the ability to produce the top-entry version continued, as this new and unused example from 1998 proves. I am unsure if left-over castings and gear trays from the 1980s, when the requirement for this version of the Beta 5 was arguably higher, were used and made up into new lanterns until stocks ran out, or whether the tooling and dies were retained for producing new top-entry lanterns; I would suspect the former, particularly when the side-entry version underwent a minor redesign in the late 1980s, but not the top-entry version.

Given that this lantern's canopy is little-changed from that of the top-entry AEI Amber Minor (that appeared in the 1960s), it seems quite bulky for a lantern dating from the 1990s, which explains why Thorn modernised the more popular side-entry version.


The aluminium canopies of the older Beta 5s were painted a light grey colour; this tended to wear off over time whilst installed on the street, revealing the canopy's natural aluminium finish instead. The painted canopy idea was abandoned with the commencement of the new style of Beta 5 entering production (presumably, on cost-saving grounds) - the aluminium being of a sufficiently-high grade that would ensure high corrosion resistance without the need for additional protection being applied. Notice that this lantern is undrilled for a NEMA socket, although the position where it would be fitted is obvious. The lantern is designed for attaching to a " BSP male thread.


The lantern's bowl is wrapped in a polythene bag - a sacrificial anti-scratch measure for the bowl prior to the lantern's installation.


Opening the bowl reveals the three-quarter length gear tray that is common to this version of the lantern. This too dates from the Amber Minor days, with the indentations that are visible on parts of the gear tray being a means of raising the original leak transformer ballast (which took up most of the gear tray on its own) - a possible anti-corrosion measure that ensured the ballast wasn't in contact with any pools of water that gathered on the gear tray. My 1970 Beta 5 contains the much larger gear.


A contemporary Thorn label is present in the top-right corner of the gear tray.


A single screw holds the gear tray in place under normal circumstances. With this released, the tray hinges down, revealing the control gear components that run the lamp.


A Thorn G53332.4 35 / 55 Watt SOX ballast is fitted, along with a G53311 ignitor and 6 F Power Factor correction capacitor (which was manufactured on week 27 of 1998: 29th June - 5th July).


Philips MI 26 4 | Thorn Isaro Pro S




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