Thorn Gamma-6 55w geared lantern. One of the more difficult-to-find members of the Gamma-6 family is the 55w SOX geared version of the lantern that dates from the early 1970's. These first generation 'geared' Gamma-6's incorporated a large leak transformer for use with either 35w or 55w sodium lamps, and required a deep-sided base into which the bulky control gear could be fitted. The 55w version had an extension to the canopy to allow the fitment of the longer 55w SOX lamp; the 35w version doesn't have this feature. However, Thorn later developed a smaller, dedicated ballast for the 35w SOX version, so the Gamma-6's base unit was downsized and the lantern was remodelled and became a popular seller for the Company. It's possible that the 55w  SOX lamped model was discontinued around this time.

Two general side views of this unusual Gamma-6 lantern for 55w SOX lamps. Left: The lantern in acquired condition with yellowed bowl, and also showing how the aluminium canopy has been extended to accommodate the longer 55w SOX lamp. Incidentally, this example looks slightly taller than it actually is, because it is still attached to the column top, from which it was cut. The lantern is fitted with a Zodion SS4 photocell. Right: The same lantern seen with a replacement cone and Royce Thompson, Monostar-1000 photocell.

In the same fashion as later model Gamma-6's, the NEMA socket for the photocell is to be found on the top of the lantern's canopy (seen here with the photocell removed).

Unscrewing the plastic securing ring allows for the removal of the thin aluminium canopy.

With the securing ring removed, the canopy can then be lifted clear of the lantern and access gained to the interior. The 35w version of this early Gamma-6 is easily recogonisable, as it lacks the raised section to the canopy.

With the canopy removed, the NEMA socket is revealed, as is the lampholder assembly and cone retaining cover.

To remove the cone and its retaining cover, the two securing nuts have to first be unscrewed.

With the cone retaining cover and the plastic cone removed, we can now see why the base of the lantern is so deep, as it contains the lamp's bulky control gear.

By lifting the control gear tray clear, the huge Thorn AME 53131-4 leak transformer designed for use with either 35w or 55w SOX lamps is revealed, along with the capacitor and fuse holder.

 A view of the general assembly of the Gamma-6 complete with its 55w SOX lamp. Also note that even with the uplifted lamp holder, the 55w SOX lamp is only just accommodated in the available space. The plastic prismatic cone is still available from Thorn Lighting, as it was used on subsequent versions of the Gamma-6 lantern, and is also used on the current Thorn 'Basique' lantern.

 This is an identical 55w Thorn Gamma-6, and is pictured languishing away on the now disused airfield at RAF Newton in Nottinghamshire. It would appear that the 55w  model of the Gamma-6 was the lantern of choice for the RAF in the early 1970's and was used on many of its air bases.

A example of the later remodellled 35w Gamma-6 with the smaller base compartment. This dented example is seen in Borrowash in South Derbyshire.