LED DIY Replacement Lamps

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I was given 4 interesting decimal digit displays some years ago which had been part of airfield equipment which was being upgraded. These use 10 tiny 28-volt bulbs for each digit, each illuminating a clear plastic slide etched with the numbers 0-9, a precursor to the 7-segment display. I wanted to upgrade the displays to LED illumination with the possibility of building a retro clock of some sort.

The bulbs are a miniature T1-3/4 size which are 5mm, but have a wider flange so a 5mm white LED wouldn't be a direct replacement. 12-volt LEDs are available in the T1-3/4 size, but at about £3 each this would cost me £120 to replace all 40 so that was a nonstarter.
After some thought, I hit on this alternative. M5 washers with a 10mm outer diameter, solder the anode to the washer and bend the cathode roughly into the middle.

Cheap and works!



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