pc_light
Enlightened
Got my hands on a very used Streamlight SL-20X, this is the old 5x 1/2-D NiCd cell Xenon incandescent behemoth that was a popular security duty light back in the day. It was popular because it could double as a club, which is probably all that was left in this one.
But I couldn't let this old flashlight go quietly into the night, it had to rage or at least shine a little more before being put to pasture or in the draw. What to do?
Back when this light was still popular, there were a few modders who put together some fantastic drop-ins. Terralux had an off-the-shelf that might still be available somewhere as New=Old-Stock for like $100?!. But where's the fun in that. So off I went to cobble the basic parts of a LED upgrade - a light engine/emitter and a reflector.
LIGHT ENGINE
------------
New, a fully charged NiCd battery pack (as originally equipped) or NiMH power pack (aftermarket upgrade) would be 6V+. The installed used batteries measured 4.2V after an overnight charge. So something in the 3-6V range would be perfect. Well that happens to be a very common P60 drop-in voltage range, and I happen to have a P60 LED drop-in on hand, so perfect.
I decided to see how much juice was left in these old batteries and to my surprise, they still managed to provide usable light, such as it was for an old incan bulb, of almost 2-hrs. The batteries were pretty much depleted at the end though, measuring less than 1V. Usable.
EMITTER
-------
I prefer warm tints boarding the neutral (4000-4500K) range. Looking into my box of available LED's I had a 4250-4500K XT-E R2 on 16mm MCPCB that wasn't destined for any projects. The XT-E has a good/low V-forward of 2.77 @350ma and good "throw" profile as well, so it was drafted for this mod.
Next finding and setting the correct reflector size and focal point.
REFLECTOR
---------
The first choice was to salvage the existing reflector from the old incan light module. Those reflectors are quite large and deep, so I was hoping to avoid having to source a substitute for something this specialized. I had concerns about the hardiness of the OEM reflector which felt light and plasticy. But once I got the lamp module apart, I was pleasantly surprised to find that it was actually aluminum. It wasn't polished like other aluminum reflectors (some even refer the the reflector finish as being "fogged") but it was perfect OEM fit and being aluminum it would help conduct any heat as well, perfect.
The original beam is a ringy splotch, typical of old weak incan bulbs (the exception being Surefire and other quality bulbs.) But it still had a focused hot spot. Typical of bulb-reflector set-ups the bulb sat deeper into the reflector (from the bottom) to achieve it's focal point. Whereas reflectors designed specifically for LED's, and CREE's in particular, are designed to capture/reflect light at the very bottom/base of the reflector at or near the small opening.
After some trial and error I determined that the ideal placement required for a good hot-spot was approximately 6-6.5mm into the reflector. The typical MCPCB mounted LED sitting at the bottom of the base opening of the reflector was out of the question. It would need one of those post mounted LED's similar to the LED bulb clones that are sold as direct bulb-only drop-in replacements, in order for the LED to be positioned at the correct depth for a good hot-spot.
An alternative method to raising the LED into the reflector is to cut down the reflector until the LED is positioned at that same correct relative position inside the reflector. (This doesn't always work, it depends entirely on how the original reflector was designed and the emission pattern of the light source of the intended design.)
I prepared my first trial placement in the reflector and would raise the emitter as necessary to hit the focal point. The first position was with the board (16mm) sitting inside the reflector resting at the bottom, touching the sides of the reflector. By shear dumb luck, that placement was almost precisely where the focal point formed a tight hot-spot. Ironically I think it was too tight/small so I decided to lift it a fraction of a mm to make it a little larger for medium distance illumination (~35-50 ft). This had the effect of creating a "doughnut" visible when viewed at less than 10-ft but since most usage would be at greater distances, this was acceptable.
The pictures -
Original SL-20X beam (left) at 3-ft vs Modded with XT-E (right).
On the same battery at same charge level (~3.5V). The difference is night and day.
Comparison to some other classic lights with throw -
P60 Host with Malkoff M61NL Drop-in (left) ) - Streamlight SL-20X, modded (center) - Stock SF L6 (right)
Lights in same order, at about 3-ft from wall; (large spill from SL-20X is barely visible in photo but clearly visible in person)
Same photo, stopped down. ("Doughnut")
The hot-spots are comparable in intensity. The Modded SL-20X hot-spot appears to be slightly larger, which bears out when shone at greater distances; the doughnut pretty much disappears starting after about 10-ft. The SL-20X has the largest overall "spill", not as intense as the smaller more intense Malkoff or the L6 spill but definitely usable.
The Malkoff is spec'd as being 160 Lumen and the L6 as 100, my best estimate for the SL-20X LED Mod would be about 100+ lumen in total.
I have not performed run-times and I probably won't because to be meaningful I would need to test it with a new/fresh battery pack. Since I don't plan on purchasing one for this old light, I'll never know. I can verify that it runs over 2-hrs now on the current old batteries. A new set of batteries should provide 4-6 or more hrs?!
Front end, the MCPCB actually sits inside the reflector rather than under it. I mounted it in place using Artic Silver Epoxy. So it should stay put.
Overall light MODule, sits inside light. It's attached to the reflector and wedged inside on top of the switch module. Free floating but very snug and I think secure. Should survive drop tests but perhaps not repeated clubbing
It's still only a single mode light but with a tailcap mod might be capable of Hi-Lo. Alterations were limited to the reflector/lamp assembly, thus it could be reverted back to original by simply replacing the LED Mod with an OEM lamp module. So an old solder get one last hurrah.
Enjoy.
But I couldn't let this old flashlight go quietly into the night, it had to rage or at least shine a little more before being put to pasture or in the draw. What to do?
Back when this light was still popular, there were a few modders who put together some fantastic drop-ins. Terralux had an off-the-shelf that might still be available somewhere as New=Old-Stock for like $100?!. But where's the fun in that. So off I went to cobble the basic parts of a LED upgrade - a light engine/emitter and a reflector.
LIGHT ENGINE
------------
New, a fully charged NiCd battery pack (as originally equipped) or NiMH power pack (aftermarket upgrade) would be 6V+. The installed used batteries measured 4.2V after an overnight charge. So something in the 3-6V range would be perfect. Well that happens to be a very common P60 drop-in voltage range, and I happen to have a P60 LED drop-in on hand, so perfect.
I decided to see how much juice was left in these old batteries and to my surprise, they still managed to provide usable light, such as it was for an old incan bulb, of almost 2-hrs. The batteries were pretty much depleted at the end though, measuring less than 1V. Usable.
EMITTER
-------
I prefer warm tints boarding the neutral (4000-4500K) range. Looking into my box of available LED's I had a 4250-4500K XT-E R2 on 16mm MCPCB that wasn't destined for any projects. The XT-E has a good/low V-forward of 2.77 @350ma and good "throw" profile as well, so it was drafted for this mod.
Next finding and setting the correct reflector size and focal point.
REFLECTOR
---------
The first choice was to salvage the existing reflector from the old incan light module. Those reflectors are quite large and deep, so I was hoping to avoid having to source a substitute for something this specialized. I had concerns about the hardiness of the OEM reflector which felt light and plasticy. But once I got the lamp module apart, I was pleasantly surprised to find that it was actually aluminum. It wasn't polished like other aluminum reflectors (some even refer the the reflector finish as being "fogged") but it was perfect OEM fit and being aluminum it would help conduct any heat as well, perfect.
The original beam is a ringy splotch, typical of old weak incan bulbs (the exception being Surefire and other quality bulbs.) But it still had a focused hot spot. Typical of bulb-reflector set-ups the bulb sat deeper into the reflector (from the bottom) to achieve it's focal point. Whereas reflectors designed specifically for LED's, and CREE's in particular, are designed to capture/reflect light at the very bottom/base of the reflector at or near the small opening.
After some trial and error I determined that the ideal placement required for a good hot-spot was approximately 6-6.5mm into the reflector. The typical MCPCB mounted LED sitting at the bottom of the base opening of the reflector was out of the question. It would need one of those post mounted LED's similar to the LED bulb clones that are sold as direct bulb-only drop-in replacements, in order for the LED to be positioned at the correct depth for a good hot-spot.
An alternative method to raising the LED into the reflector is to cut down the reflector until the LED is positioned at that same correct relative position inside the reflector. (This doesn't always work, it depends entirely on how the original reflector was designed and the emission pattern of the light source of the intended design.)
I prepared my first trial placement in the reflector and would raise the emitter as necessary to hit the focal point. The first position was with the board (16mm) sitting inside the reflector resting at the bottom, touching the sides of the reflector. By shear dumb luck, that placement was almost precisely where the focal point formed a tight hot-spot. Ironically I think it was too tight/small so I decided to lift it a fraction of a mm to make it a little larger for medium distance illumination (~35-50 ft). This had the effect of creating a "doughnut" visible when viewed at less than 10-ft but since most usage would be at greater distances, this was acceptable.
The pictures -
Original SL-20X beam (left) at 3-ft vs Modded with XT-E (right).
On the same battery at same charge level (~3.5V). The difference is night and day.
Comparison to some other classic lights with throw -
P60 Host with Malkoff M61NL Drop-in (left) ) - Streamlight SL-20X, modded (center) - Stock SF L6 (right)
Lights in same order, at about 3-ft from wall; (large spill from SL-20X is barely visible in photo but clearly visible in person)
Same photo, stopped down. ("Doughnut"
)
The hot-spots are comparable in intensity. The Modded SL-20X hot-spot appears to be slightly larger, which bears out when shone at greater distances; the doughnut pretty much disappears starting after about 10-ft. The SL-20X has the largest overall "spill", not as intense as the smaller more intense Malkoff or the L6 spill but definitely usable.
The Malkoff is spec'd as being 160 Lumen and the L6 as 100, my best estimate for the SL-20X LED Mod would be about 100+ lumen in total.
I have not performed run-times and I probably won't because to be meaningful I would need to test it with a new/fresh battery pack. Since I don't plan on purchasing one for this old light, I'll never know. I can verify that it runs over 2-hrs now on the current old batteries. A new set of batteries should provide 4-6 or more hrs?!
Front end, the MCPCB actually sits inside the reflector rather than under it. I mounted it in place using Artic Silver Epoxy. So it should stay put.
Overall light MODule, sits inside light. It's attached to the reflector and wedged inside on top of the switch module. Free floating but very snug and I think secure. Should survive drop tests but perhaps not repeated clubbing
It's still only a single mode light but with a tailcap mod might be capable of Hi-Lo. Alterations were limited to the reflector/lamp assembly, thus it could be reverted back to original by simply replacing the LED Mod with an OEM lamp module. So an old solder get one last hurrah.
Enjoy.
Last edited:
