As stated above, go to the Dealer's Corner in the Marketplace and look for AW's tower kit. These are the same parts as in the Arcmania towers, but in kit form. You build an LED tower that replaces the SF incandescent lamp assembly in your M4.
A good choice for the LED tower is the Seoul version. Then get a Seoul P4 U2 bin LED from PhotonFanatic. You also need
- 24 gauge hookup wire, preferably teflon coated instead of standard PVC (available from a guy named mudman cj on the Custom and Mod B/S/T forum). PVC insulation has a tendency to shrink back and you have to be quick with your soldering iron. A good soldering job with minimal insulation shrinkage can be done using PVC coated wire, but it is easier with teflon coated wire.
- driver board (SOB 917 or SOB 1000 from The Sandwich Shoppe works well)
- clear nail polish
- isopropyl (rubbing) alcohol (for cleaning any finger oils from the top of the tower and the LED's slug)
- thermal epoxy (one choice is Arctic Alumina thermal adhesive, not thermal compound, from PhotonFanatic or The Sandwich Shoppe)
- soldering iron and solder
- diagonal wire cutter (to trim the leads from the LED -- clearance through the hole in the reflector is tight)
- small screwdriver to tighten the M2 ground screw to the tower (a magnetic tip makes life easier too)
A spare 3.7V Li-ion cell, some small magnets, a known-good LED, and some extra hookup wire are also useful to test driver board for function before you start assembling the kit. Once you verify that the driver board works, you can also test your Seoul P4 for function.
I've mic'ed the AW tower and it comes out a little taller than the yclo tower -- about 0.015" taller. If this is an issue, you can get some shims from McMaster-Carr (they sell some very thin shims) to compensate for the extra height of the AW tower. I haven't noticed any beam quality issue in my AW tower in a SureFire T-62 turbohead and a SureFire SRTH, but your turbohead may be different.
Assembly is reasonably straightforward. It might be easier to feed the wire leads through the center channel by starting from the top instead of from the bottom. I soldered the wire leads to the sides of the LED terminal leads, not on top of them. This was because of the tight clearance that the tower has to fit through the hole in the reflector. I also trimmed and then folded down the long LED terminal leads as flat as possible against the side the black plastic LED case and trimmed back the notched and unnotched leads that also stick out.
During assembly, the Seoul P4's dome (which is sticky) may collect foreign material. You can use a lintless microfiber cloth (such as the ones for cleaning eyeglasses) dipped in the isopropyl alcohol to clean the dome. I used a freely-dangling corner of the cloth and lightly brushed it over the dome to pick up all of the FM. Do this at the end, and then insert the completed tower into your M4.
I did not glue or solder the driver board into the base of the tower. The board fit to the tower was perfect and the friction fit was enough to keep the board in-place and perfectly flat. I also did not bother with filling the driver board cavity with thermal compound. The tower seems to run very cool (my SF 12ZM light barely got warm after a recent 15 minute continuous run), so I don't think the SOB driver board is going to suffer from heat buildup (it has some sort of built-in thermal protection anyway). IIRC, I measured about 4 watts of power into the board. Assuming 75%-85% driver board efficiency (the stated spec for the SOB), that means the board is dissipating 1 watt or less as waste heat. I suspect that driver boards such as the ones in SF 6P drop-ins run hotter than that (e.g., DX6090), and images of the DX6090 on the Deal Extreme web site don't show any thermal compound covering their driver.
If you may use this in a weaponlight, I would test the strength of the adhesive that holds the LED to the top of the tower. You don't want your LED to pop off under recoil. It might help to lightly roughen the slug and tower surfaces for better adhesion to the thermal epoxy.
