Thorn EMI Gamma 6 Traditional

Lantern acquired in January 2008.

"It's a Gamma 6, Jim, but not as we know it!" This (seemingly) rare and unusual version of the humble Gamma 6 was left over following a scheme in Leicestershire, and as such, has never been used. This version cannot be seen on any public roads in Derbyshire; however, another SON example (probably 70 W) was installed on a 6 m CU tubular steel column to the rear of one of the buildings at my school - it took me a while to realise what the lantern was!

At first glance, this version of the Gamma 6 looks nothing like the more familiar 'standard' version - but then the base casting, internal support struts and canopy locking ring give the game away as to the lantern's heritage. Interestingly, the bowl is positioned in such a way that the support struts line up with two of the corners.

The canopy is plastic, instead of aluminium as with the standard version.

The base casting remains aluminium, however.

Only with the bowl removed can the similarities with the standard version be seen. The bowl is a one-piece object and all four panels are glued together. Unlike my 70 W SON standard example, this has the ignitor positioned adjacent the lampholder as there is not space for it in the base, due to the ballast. As it happens, all is not as it seems with the base casting either...

It IS a standard base casting! A square-based section slots in on top, to provide the necessary width to support the bowl.

A Fisher-Karpark NEMA socket is fitted and still has the dust cover attached.

The capacitor is dated to September 1984, although the actual lantern may be newer than this.

The Gamma 6 was fitted to a post-top stand in October 2018. After that, it was powered up.


Lamp warm-up 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
241.1 0.34 63 82 49.9 0.77 63.12 13.12 26%

Thorn Gamma 5 | GEC 'Brookvale' Z5530




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