REFURBISHMENT OF LUCAS ST51 'D' TYPE LAMPS

I bought a pair of used Lucas ST51 lamps with the full red glass lens for the rear of the RTS Special that I am building. Although the bodies and red glass lenses were in very good condition, the bulb holders were not. One was distorted and the other partly missing. Also, the holder design was quite poor, with simple bits of bent brass for contacts.

I plan to use LED bulbs, which need a good low resistance connection as they draw very little current, so I decided to replace the bulb holders with modern equivalents. I drilled out the rivets and removed and discarded the obsolete bulb holders and brackets in readiness for the replacements.

I bought all of the parts on eBay; a piece of 18swg (1.2mm thick) steel plate for £2, a pair of steel bulb holders for £4, a silver solder and flux kit for £3 and ten copper rivets (2mm diameter x 4mm) for £1. A total outlay of £10.

By angling the fibre insulators it was easy to remove them, together with the connecting wires, from the new bulb holders. I then sanded the zinc plating off the rear of the holder bodies ready for silver soldering. New brackets were cut from the 18swg steel plate, incorporating an earth tab in the design so that an earth wire can be connected if required, rather than relying upon the mountings for a good earth. Both sides of the brackets were sanded ready for silver soldering and the edges deburred . They were then formed to shape using soft jaws in the bench vice. The bulb holders were then silver soldered to the brackets, ensuring that the wire exit holes lined up with the clearance holes in the brackets.

The finished brackets were zinc plated to prevent corrosion using a basic home setup. Finally, the completed brackets were riveted to the lamp bases using copper rivets for good contact and the insulators and wires were reinserted into the bulb holders and connectors soldered to each wire. LED bulbs fitted, job done!

Jon Reynolds DA7C