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DIY: Converting a Transilluminator into a Short Wave Lamp

My small hand-held short wave lamp is useful, but has its limitations. I was interested in a much more powerful light for display and photography. After some research and talking to collectors with large displays, I learned about the transilluminator, a piece of laboratory equipment which is essentially a large enclosed filtered UV lamp. I learned that a mid wave transilluminator can be changed into a short wave lamp by replacing the tubes, and I learned that I could gut the fixture and build an even brighter lamp. Having electronics experience myself, that was the option I chose. I bought a used transilluminator and successfully converted it into a 240 watt lamp.

I could not have performed this conversion without the excellent DIY guide on transilluminator conversion from MinerShop, written by Mark Cole. It contains useful and highly applicable advice on this topic and is required reading for anyone undertaking a similar project. I decided to document how the conversion process worked for my particular fixture from start to finish, and I present it in the photo gallery below.

Electrical work is dangerous. Do not attempt a project of this nature without a strong understanding of light fixtures, wiring, and electrical safety.

The first order of business was choosing a transilluminator with a low price and a big filter. I found a good deal on this Fisher Scientific model with a 14" x 6" filter. The glass is beat up from use and has a crack across its width, but this does not matter for my purposes and does not affect functionality.

Unsurprisingly, it's dirty inside. I used the light a few times before tearing it down. I'm kind of amazed that these UVB tubes worked, because they all fell apart when I removed them. I could simply put in new tubes for a 90w light, but I am going to take out what's here and upgrade to 240w.

Fulham Workhorse 5 ballasts and Philips TUV PL-L 60w bulbs. The best price for them was on Amazon. The 2g11 bases and the metal bulb clips I got elsewhere. I later learned that 2x60w bulbs is technically out of spec for these ballasts and 2x55w is the recommended maximum. The next model up is advised if you copy this configuration.

Checking out placements. This type of bulb does not emit light from the entirety of its glass portion. For maximum output, I want to horizontally align the portions of the bulbs which do light up, with the filter glass on the lid. I was lucky with this model; I won't have to do much to make that happen except mount the bases as far back as they will go on these rails. To do that, I just need to drill several holes. I can even arrange the bulbs in alternating directions, and they will still align properly with the filter.

Beneath the reflector, the old ballasts and wiring. For some reason there's no fuse in here, so I'll have to add one. The power cord is beat up, so I will replace it as well. Basically, this is all coming out. Only the switch and fan will be re-used.

Marking the holes for drilling required no tools because the four bases just barely fit flush inside the reflector. I drilled through the reflector and the bar below it together, then filed each smooth.

The chassis has been cleaned up and the new ballasts mounted. They are longer than the old ballasts, but by mounting diagonally, I only had to drill one extra hole in total to secure them. The drilled reflector is visible at top.

I put black silicone over the many unused holes in the chassis to block light leaks. I put it over the ballast mounting clips too, although this wasn't necessary. Examining the lid, I noticed it was flexible on its longest dimension with a lot of play, and I think that could be why the filter glass cracked. I made it dramatically more rigid using square steel tubing and epoxy. Attached to the glass is a shattered plastic diffuser, useless for UVC, so it will be removed.

A fuse and the new power cord are now installed. The fuseholder is wired with solder and heatshrink, and I used spade and ring terminals for everything else. I got a 16g power cord instead of 18g by mistake, and I had to enlarge the cord grommet to accommodate it. This made the grommet slightly wobbly, so I secured it with epoxy. I'm going to be using this device inverted from its intended orientation, so I rotated the power switch to make the on position correspond to the new "up".

Shunting and wiring the bases.

The wiring completed. I checked my work using an ohmmeter.

The reflector and hardware mounted.

The sides and lid reattached, and the bulbs installed.

It powers up, that's a good sign. Let's see how it works.

Wow, it sure is bright. There are some tiny light leaks in the top corners, and some big leaks from the air vents. I experimented with attaching foam inside the air vent panels to block this light, but it also restricted the airflow too much to allow sufficient cooling. I heard steel wool works, but I don't trust it around electricity. I will just flip the panels so that the openings point downwards, which only requires drilling a few new screw holes.

The vent panels have been drilled and rotated, and the old holes filled with black silicone, as well as the gaps in the corners that leaked.

Everything fires downward now, and it looks super clean.

Extreme heat can crack the glass, is bad for the lifespan of the components, and reduces UV output. This model of transilluminator has a powerful fan and ample empty space inside for proper airflow and cooling. My new components and altered design also do not take up any more space inside than what was there before. So despite the higher wattage, after leaving it on for an hour, it gets warm, but it never gets hot. The heat distributes evenly, and the fan does its job. I can hold my (nitrile glove protected) fingers against the warmest part of the glass without discomfort.

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