GEC Z5760

(Not to be confused with the Z5670, which is a post-top lantern).

This fitting came from John Mitchell, and arrived here on Saturday, 24th April 2010.

The bulkhead can be identified by its tapered construction and opal polycarbonate cover. The black parts of this fitting are of die-cast aluminium, making for a tough construction. The front section hinges to the right in order to allow access to the lamp and gear. Two clips attached to the left-hand side of the fitting secure this section.

Only minor yellowing is present on the polycarbonate front section. From this angle, the bulkhead bears more than a passing resemblance to the later Philips NGX 018 bulkhead.

With the cover opened, the 35 W SOX lamp is seen. This fitting is not intended for running an 18 W lamp (the Nightwatch 18 served that purpose), so the lamp support is only suitable for lamps of the 35 W length - any shorter, and they wouldn't reach; any longer, and they would be too long for the bulkhead. The polycarbonate cover is held in place with several steel strips that clamp the plastic in place.

Removing the reflector reveals the bulkhead's control gear. When new, a GEC Z1616P ballast (with built-in ignitor) would have been fitted; this has been replaced with a modern Transtar unit. The capacitor appears to be original, however - It is dated to February 1977. Despite the bulkhead therefore being 33 years old when it entered the collection, it was in good condition and shouldn't prove too difficult to restore (famous last words!); a repaint of the aluminium bodywork should suffice.


The metallic components returned from being refurbished on Friday, 23rd July 2010. I commenced the bulkhead's rebuild on the same date, and started by attaching the back plate to the wall:

The fixing holes were significantly wider than the screws were; washers were therefore required to increase the surface area of the screw heads. Notice that the 20 mm rear cable entry hole has been plugged with a closed rubber grommet.

The components were then re-fitted to the back plate

The reflector plate had also been restored; this was painted gloss white.

The Philips-made OSRAM lamp was then re-fitted.

The front cover was then reassembled and reattached to the back plate. Thanks to Pete Greenall, the bulkhead returned to service with a brand new bowl fitted.

Power was then applied, and the bowl instantly became the ruby-red colour that is synonymous with freshly powered-up SOX lamps.

A few minutes later, and the lamp was operating at full output. At this point, I realised that the bulkhead resembled a Thorn Gamma 6 that had been thrown into a car crusher!

 

The following animation shows the bulkhead being rebuilt. Although not intentional, the adjacent Venner MSQP time switch can also be seen rotating in the animation; this rebuild did take a while to undertake!

Lamp warm-up video:

Testing the fitting 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
237.5 0.21 46 50 49.8 0.91 45.39 10.39 30

Two Z5760s, with each running an 80 W mercury lamp, are installed in Matlock Bath. Click here for more information.


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