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Picture of Magic Lantern Revamp

I got a rather nice Victorian magic lantern projector in a car boot sale. It's probably a "Walter Tyler Helioscopic Magic Lantern" from around 1890.

Like many such lanterns, it had lost its oil-lamp burner so I decided to give it an LED lamp.

It still has the reflector attached to a brass arm so I could use that to support the LED. The reflector could also act as part of the heat-sink for the LED.

(As with all such "modernisations", one should not make changes to the original antique.)

Step 1: What Kind of LED?

Picture of What Kind of LED?

My first thought was to use a flat COB LED to give even illumination. I bought:

(Or search eBay for "48 LED COB 8W".)

It's easy to install - it has a sticky back - and can be connected straight to 12V. I could stick it onto a sheet of metal but it didn't seem to need much of a heatsink.

The projector has a condenser between the "lamp" and the slide so the divergent light from the COB LED was focussed in the slide.

Unfortunately, I couldn't get a sharp image. That really surprised me. Surely all that matters for focus is that the slide is in the right place? The illumination might affect the brightness but not the focus. I knew you needed a focussed condenser for microscopy but why did it matter for a projector? The web suggested that a projector's condenser was needed for even, bright illumination but not for focus. Did I need a "point source"? Weird.