AA Mini-mag/VersaLux PR-2 mod

mahoney

Enlightened
Joined
Jan 7, 2002
Messages
603
Did I start reading Candlepower because I'm a flashaholic or did I become a flashaholic because I read Candlepower? I suspect the latter (or at least it's what I'll tell my significant other if she asks about this flashlight obsession) because last night I modified one of my Mini-Maglites, something I would not have considered before finding Candlepower. The mod was fairly easy. First, order a VersaLux PR-2 from www.techass.com. The length of the bulb is longer than the length of the Mini-mag switch and bulb that you are going to remove but you can steal some length from the tail cap. First, drill a 3/4" hole in a square or rectangular scrap of wood about 3/4" thick. Then cut the wood in half through the hole. The 2 pieces of wood can now be used to clamp the tailpiece in a vise without marring it. I used a hacksaw and a file to remove the unthreaded portion at the top of the tailcap, leaving the threads intact. This will remove the recess for the spring so I first used a 25/64" drill bit in the drill press to drill down into the tailcap to below the level of the threads and later drilled a bit deeper, stopping about .22" below the "new" top of the tailcap, leaving the top of the spring only about .06" above the tailcap when installed. The 25/64" hole is a slightly loose fit for the spring so I opened out the bottom coil just a hair. Next I used a sharp chisel to cut off the plastic flange on the top of the body and dumped the bottom part of the switch/bulb holder assembly out of the bottom end of the body. I sanded the top of the body tube to remove the anodizing (?) and expose some aluminium, perhaps not necessary. The hole in the top of the body was a bit bigger in diameter than the PR-2 bulb, a bit of luck. I next insulated the body of the PR-2 bulb below the flange by using heat shrink tube and a small heat gun. I figured if I could hold the bulb in my fingers while doing it I wouldn't get the LED too hot. A few wraps of good electrical tape would probably work just as well. I then tested the bulb in the body by pushing it in the hole with batteries and the endcap installed and found, as I suspected I would, that I needed a washer to take up the remaining space between the top of the body and flange. If I had been willing to wait and make a trip to the hardware store I probably could have found an easier solution but I pressed on and found a brass washer in the shop that had too big an OD and too small an ID. The OD sized easily with a little time at the belt sander but sizing the ID was a tricky process involving a repairmans taper reamer, a vise, and a small pair of Vise-grips. This done and the bulb lighting when pressed down into the body so the flange and washer made contact with the top of the body, all that remained was to open out the hole in the reflector. I did this with a couple of reamers, very carefully. Wanting to conserve length and provide a good bearing surface on the bottom of the reflector to press against the flange on the PR-2, I opened out the hole so the flange rested on the ribs at the bottom of the reflector. Big mistake. The beam pattern turned out to be the dreaded "bright ring of light surrounding a black hole" so familiar to Mini-Mag users. Some experiementation revealed that the flange should be about .1" below the reflector for a reasonable spot focus so some plastic of about the right thickness was found and another washer made. I may try a few different thickness washers to refine and smooth out the hotspot but the light now has a decent small hotspot surrounded by an even pool. The flashlight is about 3/16" longer than a regular Mini-mag because the head is unscrewed slightly to accomodate the extra washers but the o-ring is still well covered by the head. To turn on the light I simply tighten the head slightly. The focusing ability is of course lost. Current draw from 2 fairly new alkaline batteries is 90 ma. A brief visit to the co-worker with the light meter yielded the following hotspot readings; 30 Fc at 6", 1.2 Fc at 6'. To get these readings I did have to endure a bit of ribbing about using the $1000+ meter to test "another of my cheap flashlights". Not as bright as the Mini-mag it started out as but with more usefull light in the pool. The center of the hotspot is really blue but otherwise I like it and it will probably keep me happy until the Arc LS is available again. Of course, if I came up with the $40, that LEDCORP pro series PR2 bulb would probably drop right in...hmm...see what you guys started!
 
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