GEC Z9464

Lantern acquired in April 2003.

This is an early design for the gear-in-head version of the Z9454 (the '6' denoting the presence of gear), and because things from the past were 'built to last' (I am a poet and I do not know it!), the original 1950s' control gear not only remains installed in the inside of the lantern's canopy, but it is also still in operable condition. Although Z9464s exist in Derbyshire, all are of a later type, with their canopies matching those of the Z9454. Owing to the size of the gear components in this lantern, the canopy is deeper. As mentioned on the Z9454's page, this lantern came from the former army depot in Hilton, Derbyshire, when the site was being cleared, in order to make way for new housing.

With thanks to 'Odeon Master' for permission, this picture depicts how the Z9464s looked when installed at the depot site. All were attached to these distinctive concrete wall brackets; the use of gear-in-head lanterns being a necessity on account of there being no space on the bracket, or within the buildings, for housing separate control gear.

 

The lantern comprises a die-cast aluminium canopy and acrylic (Perspex) refractor bowl. When new, the bowl would have been transparent; however, years of UV degradation from the sun has turned much of the material translucent white. The plastic is noticeably thinner than it is on later versions of this lantern. Newer bowls are not directly interchangeable as the hinge mechanism differs slightly - this would require adapting before a newer bowl could be used.

 

From above, the rather angular appearance of the canopy is apparent. The circle that is visible in the centre of the canopy is where the pattern would be changed on the top-entry version - the Z9465.

 

The distinctive round bottom to this range of lantern bowls is slightly more transparent than the rest of the plastic is - this being because it wasn't in direct sunlight when in use. Another change made by GEC on later versions of this lantern was the addition of refractor prisms in the area directly beneath the lamp. A thin aluminium retaining ring is attached to the bowl's rim, and the hinges are riveted to this. The retaining ring causes the bowl to be slightly too wide for the bowl to 'sit' correctly - notice the slight bend around the support clip. In order to undo the clip, gentle pressure must be placed on this part of the bowl, which pushes it in sufficiently for the rigid wire that makes up the clip to pass beneath its anchor point and into the released position.

 

The very top portion of the bowl is also free from discolouring; the canopy shielding this portion of the bowl from sunlight.

 

With the bowl removed, the lantern's innards (including the rusty gear tray/reflector) of course become visible. Although a 90 W SOX lamp is fitted here, these lanterns were designed to run 140 W SO/H lamps - these are the same physical size (and have the same operating characteristics) as a 90 W SOX does. If only I had an OSRAM 140 W SO/H lamp to fit in this lantern...

 

Funny that I should say that! Although the already-worn arc tube of the SO/H lamp was damaged when it entered my collection, owing to the glass around the electrodes being weakened, the oxidation of the sodium is now complete; hence, the powdery-white appearance of the arc tube.

 

I wonder how many years it is since a SO/H lamp was last fitted in this lantern.

 

With the lamp removed, the distribution of the rust on the reflector can be appreciated - it is more prominent to the rear of the lantern as the integral leak transformer is situated at the front of the lantern; this would provide sufficient heat to reduce the rusting during operation. The handwritten message of 'blast' is not my response to discovering that the sodium in the old arc tube had oxidised; it is actually a reminder for me to arrange for the reflector to be sandblasted/repainted as part of its restoration work!

 

Peering into the open void at the front of the reflector, the rusted heart of this lantern is visible.

 

Removing the reflector reveals the reason as to why this lantern is so unbelievably heavy - the massive open-coil leak transformer, and, to a lesser extent, the long aluminium capacitor. Unfortunately, owing to the age of the lantern, all of the internal wiring is asbestos-sheathed. The original cable clamp and terminal block are missing, with the result that a replacement (floating) terminal block connects the modern PVC supply cable to the lantern's internal wiring. Typically, one of the two 732 (an imperial size that is slightly smaller than 6 mm) grub screws was able to be freed with little effort; however, the other grub screw is currently seized. The remains of the inner steel tube of the concrete wall bracket to which the lantern formerly attached are still very much a part of this lantern, and I suspect that even if both of the grub screws could be removed, the tube may remain resolutely wedged in place.

 

Although rather crude in its appearance, we have to remember that certain materials, particularly steel, in post-war Britain continued to be in short supply for some time. The tape surrounding the two windings of the transformer is beginning to degrade. A simple eight-way connector attached to the front of the transformer allows for the individual cables to terminate into it. From left-to-right, the terminals serve the following purposes:

1) Lamp; 2) Neutral / Capacitor; 3, 4 and 5) Alternate mains voltage tappings - not used here; 6) Live; 7) Capacitor; 8) Lamp

 

An almost-fossilised tag advising of the different terminals to use on the leak transformer for different mains voltages was found behind the manufacturer's plate on the ballast. The tag has broken in several places; I therefore placed the individual pieces together for this picture. The parts of the tag that are still yellow were located behind the plate; the more discoloured parts protruded above it. Originally, the eyelet would have had a piece of string (whose length I know not) passing through it; the other end attaching to a part of the transformer. A tiny fragment of the string still survived behind the plate - hats off to whoever installed this lantern all those years ago, as I would imagine that these tags were often discarded after installation, and the leak transformers had been connected as per local supply voltage requirements.

 

The aluminium-cased GEC capacitor is rated at 20 F. Given its age, this probably contains Polychlorinated Biphenyl (PCB) oil - you know that when something sounds dangerous, it probably is, and this is no exception - PCBs were later discovered to be both carcinogenic in humans, and also extremely polluting in nature. Fortunately, this capacitor shows no signs of leakage, and as I am unlikely to hack it open any time soon, the risk is reduced.

 

A rubber gaiter (bearing the GEC logo) exists at one end of the capacitor, in order to allow connections to be made. At the other end, the cryptic code '40 58 22' is stamped on the casing - if this is a date code, I am unsure of how to decipher it - is '58' 1958, for example? This sounds plausible, as I am doubtful that '40' would relate to 1940 - and '22' is definitely not 1922 - low pressure sodium lamps were not available commercially until a decade later.

 

Another view of the leak transformer; this time, with the wires removed in order that the details on the plate can be read. The aforementioned fragment of string can be seen to the bottom-right of the plate. The serial number for the transformer is 206884. Incidentally, the reason for de-wiring the leak transformer was to allow for the asbestos-sheathed wiring to be replaced with modern PVC wiring, which of course, is not harmful at all..!

 

This video demonstrates the sonorous hum emitted by the leak transformer during operation.

Owing to the bowl being translucent, the plastic is changed to a solid block of yellow-orange light, once the lamp has warmed up.

 

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
240.2 0.79 113 190 49.9 0.59 111.96 21.96 24

GEC Z9450 | GEC Z5698U


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