[ajgriff]

PART 1 - BIN OR MEND?

At the risk of becoming known as 'the idiot and the lamp' I felt the need to share my experiences restoring this desk light.

I'm currently in the midst of a Tektronix 465B restoration but was recently distracted (happens a lot) when I spotted this lamp at my favourite local flea market. Something about it made me think it might actually work quite well as an adjustable workshop light. As it turns out Captain Kirk thought much the same as Jazz lamps were used as props in the Star Trek VI film. Luckily for him the good Captain's lamps had not been abused by Klingons, unlike my example. Actually I think Kirk may have been an Admiral by the time this film was made in 1991.

A thorough examination of the lamp revealed the following issues:

1. One of the hinges had failed. This was the most serious fault as the hinge structure also forms part of the electrical circuit connecting the halogen bulb to the dimmer circuit. Yes, it has a dimmer facility.

2. The swinging arm is counterbalanced by springs hooked to the hinges at one end and plastic posts at the other. The spring post for the broken hinge had sheared.

3. The two lugs holding the case screws at the back had disintegrated.

4. The neon mains indicator bulb had died - probably not caused by a Klingon.

It didn't take too long to figure out possible ways to repair 2, 3 & 4. However, each hinge is part of an alloy casting extending into the sealed swinging arm. Much as I tried I couldn't find a way to access the castings without potentially destroying the arm and its slide rule mechanism in the process. It was also clear that the failed casting could only realistically be repaired by soldering with an iron in order to restore electrical continuity and some degree of structural integrity. My experiences of trying to solder cast alloys have not been good. Also it was difficult to see how to gain access to the site of the breakage inside the plastic moulding. At this point the desk lamp came within a whisker of being thrown into the parts bin (decent toroidal transformer and dimmer circuitry). However, before taking aim I scraped the alloy with a sharp point and miraculously revealed signs of copper content. Maybe soldering was an option after all.

The next step was to see if the alloy would take solder so out came the trusty Weller TCP with a medium temperature bit fitted. To my surprise, after thorough preparation the solder (standard leaded fare) flowed and stuck firm. As this was 'proof of concept' could I now gain access to the break inside the moulded plastic arm? This was achieved by weakening the plastic around the break with a sharp knife and a bit of levering with a small screwdriver. Eventually some method of disguising the ugly scar would need to be devised.

The joint was soldered using two short pieces of stout copper wire as reinforcement and to achieve good electrical continuity. The casting now seemed to have reasonable structural rigidity and partial reassembly of the unit showed that electrically everything functioned properly, except for the neon of course. After clamping the hinge end of the casting I applied some super glue to the repair. Araldite epoxy was then used to fill the gaps and cover the repair. When set the epoxy was carefully pared level with the surrounding plastic using a freshly honed wood carving chisel. Araldite is quite soft until fully cured. I'm pretty sure that the completed repair is at least as strong the undamaged hinge, bearing in mind that this is the weakest point of the casting. Time will tell.

The remains of the two damaged case fixing lugs were cut away (sharp chisel again) as well as the spring posts. Only one of the spring posts was broken but this was a clear design weakness so I decided to use a more robust arrangement using two bolts. The threads act as a means of appropriately locating the spring hooks. I've never had any success recreating lugs for self tapping screws so I opted for bolts passing through both halves of the case to replace the rear self tappers. Although the bolt heads were countersunk this still left them visible on the top surface of the case. More disguise needed.

The dead neon was replaced with a couple of sub-miniature versions that I had in stock. The current rating (about 0.25mA) was clearly much lower than the original so one of the two existing 56k series resistors was changed for a 270k alternative. The new neons were wired in series.

With all the main issues sorted I was still faced with the problem of how to disguise the hinge repair and the exposed bolt heads. The solution I came up with is a technique I've used before for concealing blemishes involving peelable self-adhesive stickers. These were developed using photo-editing software with the intention of producing something in keeping with the style of the lamp, all a bit crude but reasonably simple to achieve.

Hopefully the attached photos will help to clarify my ramblings.

Part 2 provides more information about this unusual adjustable desk lamp including its provenance and functionality along with more photos.


Alan