Thorn Gamma 5

This somewhat unusual version of the Gamma 5 came from a footpath on Holly Court in Mickleover. The lantern was replaced on Tuesday, 22nd January 2008 - an WRTL Arc running a 100 Watt SON-T lamp was used as the replacement lantern. The higher wattage was chosen following requests for the light levels in the courtyard area to be increased significantly - well, that will, certainly, be happening now! SOX Gamma 5s were used in small numbers in the Derby area - typically, providing illumination for footpaths in-between blocks of flats. Most of these were replaced with Beta 5s on mid-hinged columns.

The first few photographs show the lantern as it appeared when installed - it was believed to be the last SOX Gamma 5 in Derby, though Mickleover's 'Silverhill' estate (of which, Holly Court is a part) had many of these examples on its footpaths originally; all of these being replaced with other 35 Watt SOX lanterns, including GEC Z5698Us (in small numbers), along with sister lanterns the Gamma 6 and Beta 5.

The zoomed-in image of the lantern reveals that the canopy was not fitted correctly at the time of photographing in July 2006.

A little later the same evening, the lantern was running very healthily. A Gamma 6 running is visible to the right of the picture.

This image shows my dear Granddad and his dog, Sam, on Vicarage Road park (also part of Silverhill) in 1982. Another column supporting a Gamma 5 is visible on the footpath in the background.

A close-up of the Gamma 5 installation. This column was replaced with a newer base-hinged example fitted with a Beta 5 in later years (the example in the link is the next column to the left - not visible here).

The lantern is identical in appearance to another Gamma 5 in my collection, apart from the addition of the SS55 detector on this version. The two canopy retaining screws can be seen to the left of the lantern. It is currently difficult to fit both screws due to the support struts having been bent out of shape over the years; this is likely to be why the canopy was seen to be fitted incorrectly in the earlier image.

Externally, the canopy is very clean - only the outer rim shows signs of dirt. Internally there is more dirt, but it is mainly on the part that would be directly above the lamp.

The insides of the bowl and spigot are also in need of cleaning.

The outer bulb of the lamp has completely blackened, meaning that the lantern would have emitted virtually no useful light in its last days of operation. The lamp only just fits inside the lantern! An interesting feature to note here is that there is a built-in connector to allow the cell detector to be disconnected in the lantern while maintenance is being carried out, in order that the canopy is not straining on the wires.

With the lamp removed, the simple wiring in the lantern is shown - judging by the amount of green muck in the bottom of the bowl, this lantern often had water gathering in it - not good when the supply cable connector is also in there!

Following restoration, the lantern was reassembled and then wired up. The original Thorn gear was used, and a Thorn 35 Watt SOX lamp was fitted for authenticity.

The translucence of the bowl means that a fair amount of light actually reflects off it!

With the canopy back in place, the 'correct' optical performance is achieved.

The Gamma 5's control gear, now housed in a plastic enclosure, comprises a G53312.4 ballast, G53311.4 ignitor and G.C.2435 capacitor. Out of all of these components, the ballast is likely to be the only original one. This appears to have the date code '50', which would date it to February 1972, and seems to be accurate for this style of ballast, and possibly when Holly Court was constructed too, though there is no mention of a SOX Gamma 5 in Thorn catalogues until the 1977 edition, and even then, this lantern's label makes no mention of any other light sources except for GLS and SON.

Lantern warm-up video:

AEC Uno | Thorn EMI Gamma 6 Traditional

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