Thorn Gamma 6

Following the commencement of the Derby Street Lighting PFI in Mickleover in early 2010, this lantern and its associated column (97882) were earmarked for replacement. I decided to try to save this lantern for the Collection, as it differed from most other Gamma 6s in the area. Thankfully, I was successful in acquiring the lantern after the column had been disconnected, and so, on Friday, 7th May 2010, I picked it up from the depot.

The following is the inventory record for this installation. This record is as it was in 1997, when Derby City Council took control of its own street lighting repairs from the County Council, and long before the Gamma 6 was fitted. Therefore, any changes made after this date are not shown.

Unique Number: 97882 Location: F/P SIDE NO 14 (1ST)
Postcode: DE3 5NN Road: HINDSCARTH CR
Road Number:   Parish: MICKLEOVER
Sequence Number: 5 Patrol: Y06
       
Lamp Type: SXPL3 Wattage: 35  W Control Type: PE1
Lamps/Lantern: 1 Lanterns/Unit: 1 Control Setting: 3
Lantern Type: PT Lantern Manuf:   Control Gear:  
Height: 5  m Support Type: DD RAISE & LOWER COL - PAINTED
Bracket Proj'n.:    m Support Finish: P PAINTED COL/SIGN/PILL/GANTRY
Bracket Type:   U/G or O/H: U UNDERGROUND
Board Code: E76 Status Code: 0 USUAL / NORMAL
Service Owner: A Is this lamp/sign an Isolation Point ?: N
EB Order number:      
No-supply sheet: 0 Isol Pt: 60410 / Circuit: 1 / Seq: 1
    Location: OPP NO 17        
    Road: HINDSCARTH CR        
    Parish: MICKLEOVER        

A note attached to this record informs of the following repair: BALLAST W/S 40010379 24/2/97

The installation that this lantern came from, as it appeared on Thursday, 8th April 2010. Soon after these pictures were taken, a lantern was fitted to the new column, and the supply transferred.

The lantern sports the deeper canopy seen on Gamma 6s dating from the 1980s to the early 1990s, however, it turns out not to be "new old stock"; the NEMA socket and capacitor are dated to 2001, although the lantern appears to have been installed in October 2002. This therefore probably makes this one of the final Gamma 6s produced, as Thorn released the Gamma 6's successor, the Gamma Basique, in the same year. The lantern replaced a failed GEC Z5698U. The transparent bowl seen fitted to this lantern is also unusual in a Gamma 6.

The paint finish on the Gamma 6's canopy is still present. My other SOX Gamma 6 entered the Collection with very little paint remaining on its canopy!

Removing said canopy (and the photocell) reveals the internal construction of the lantern. The wiring to the NEMA socket and lampholder in this lantern differs from that of my other SOX Gamma 6, in that the two components share a neutral conductor in this lantern, whereas they don't in the other lantern.

The ballast is noticeably smaller in this lantern than it is in the earlier design. The ballast's support bracket has been altered to suit the smaller component.

Looking the other way, and the lantern's identification label has been relegated to being attached to the side of the base casting, due to the different ballast support bracket in this lantern.


Owing to the lantern being in good condition when removed, very little refurbishment was required - a clean and polish of the canopy, bowl and base casting, and an internal clearing of  the gear area sufficed.

The lantern was powered up on Saturday, 7th August 2010. The clear bowl fitted to this lantern made for something of a different appearance during the lantern's operation.

Lantern warm-up video:

Testing the lantern 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 (W) Percentage Difference
240.4 0.31 61 75 49.9 0.84 62.60 27.60 79

 Thorn Gamma 6 | Thorn Beta 5


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