Thorn Gamma 5

Lantern acquired in March 2005.

This and the Z5680 were removed from a caravan park in Shelton Lock in early 2005. Following their removal, short outreach brackets were fitted to the columns, and Beta 5s were installed. The lighting in the complex was all controlled off one control point, so the lanterns are completely free of holes drilled for photocells. Gamma 5s can still be seen in the City, as Survivor #4E proves; however, they are all owned by Housing Association, or occasionally can be seen inside substation complexes.

The lantern looks to be in quite a poor condition due to the spigot having lost most of its original black paint. The three grub screws in it are all currently jammed but these may work loose with some heat. If not, they will be drilled out and new grub screws will be fitted, as I had to do with the Z5670's spigot. An alternative spigot was available for this lantern, for use with Thorn's aluminium column range, but the type that this Gamma 5 uses allows it to be mounted to any 76 mm diameter column . The canopy is loose in the picture as the two locking screws on top had no threads left on them, and so they wouldn't screw down into the securing holes.

These are the two screws in question. Fortunately, Jeremy salvaged a couple from another Gamma 5 a while ago, and these will be used in place of the worn out screws.

The lantern is of a very simple construction - in fact, the lampholder is secured to the spigot and then the lamp is just changed by opening the canopy (assuming that the locking screws have threads on them of course!) and screwing it into place. The vertical line dividing the bowl into two semicircles is actually two water runs - caused by the seals around the canopy securing plates being worn out and letting moisture in over the years.

Looking inside the lantern, the two water runs can clearly be seen now. One of the old canopy screws was stuck, meaning that the canopy could only be opened a small distance. I cut the head off this screw, which then allowed the canopy to be completely removed. The simplicity of the lantern is also revealed here. (The lamp isn't particularly old but has been bashed about a bit and something has come loose inside, which keeps rubbing against the phosphor coating and wearing it off.)

The canopy isn't in a bad condition - it just requires a clean and then a repaint.

I fitted the replacement canopy screws and then put the lantern back together. This will only be a temporary measure, as the lantern will be taken to pieces, in order that I can give it a thorough cleaning.

This is the gear that powered the lamp when in use. It is probably not the original gear as the capacitor appears to be dated to 1993 and the lantern looks much older than this.

The grub screws wouldn't come loose, and so I resorted to my alternative plan and had them drilled out and replaced. The spigot was also blasted to make the aluminium smooth again. The yellow screws were used to plug the two threads on the top of the spigot, in order that they weren't damaged during the blasting.

The spigot was then repainted - all ready to be fitted back to the bowl.

The copper contacts on the lampholder were badly corroded, and so these were left in vinegar overnight, and by morning, all signs of the corrosion had gone. Meanwhile, the porcelain body of the lampholder was cleaned up. A stubborn watermark was removed by gently rubbing the area with a Brillo pad.

After a canopy repaint, the lantern was put back together.

Thorn made several different designs for the Gamma 5 bowl, including this one, with a stippled effect moulded into the plastic. This bowl came from Arthur Hind Close after the column was knocked by a digger. A close-up of this pattern is shown below. (Prolonged gazing into the photograph may have you seeing things that aren't actually there!)

This bowl is slightly more transparent than the other one - therefore it might offer a better light output.

The Gamma 5 was eventually powered up on Wednesday, 12th October 2005.

The light output from the lantern was actually quite poor, despite a new lamp being fitted.

Lantern warm-up video:

GEC Z9481 | GEC Z5680

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