Serfas HLM-1 2AA 1W Al head headlamp

cave dave

Flashlight Enthusiast
Joined
Aug 15, 2001
Messages
3,763
Location
VA
I saw this Serfas HLM1 in a bike shop. I'm sick of AAA's. Looks like somebody screwed a Dorcy(?) aluminum head to a plastic headlamp mount.

If I knew it was easy to open I'd get one to mod with a reflector and P4 as an alternative to my EOS. Anybody have one and can comment on durability and Mod potential?

6upwfn5.jpg
 

DanU

Newly Enlightened
Joined
Jan 7, 2008
Messages
15
Bringing this back up from the dead for anyone interested...

This is semi-easy to modify once you unscrew the parts. The problem is everything is glued together with a really tacky glue, so unscrewing requires a considerable amount of force.

The light is made up of three sections: an aluminum front bezel which holds the optic, an aluminum midsection which holds the "pill" for the LED and driver, and a plastic rear section which holds the switch.

The bezel is LEFT-HAND threaded, so you need to rotate it clockwise to take it off. In order to break the glue I wrapped the bezel and midsection with several layers of electrical tape to protect the aluminum from scratches and used two wrenches, one to grip the bezel and the second to grip the mid-section.

The mid-section is RIGHT-HAND threaded into the plastic rear assembly. It's a little bit easier to remove, but still required a wrench.

Once you get both the bezel off the midsection, and the midsection off the rear assembly, then you can begin to remove the pill from the midsection. It is held in by a black plastic bezel around the LED, which can be removed with some needle nose pliers, using the two holes in the plastic to rotate it out (it's right hand threaded). You can then push the pill out from the bottom with a little bit of force. It's just a snug fit, not a threaded pill like on most flashlights.

The LED sits directly on the pill (there is no LED "star"). Also the pill is connected to battery negative. This means in order to swap in a Seoul P4 LED, you need to first isolate the bottom of the LED or you will create a short circuit. I used some kapton tape from DX, but any thin insulator such as mica sheet will work. Also, there is a circular ridge on the surface of the pill which perfectly fits the Luxeon, but it is very slightly too small for the Seoul. You will need to shave off some aluminum with a file or dremel in order for the bottom of the Seoul LED to sit down far enough to make physical contact with the pill. This is criticaly important for heat transfer or the LED will burn itself out.

The driver sits in the back of the pill and is soldered in. It's a real pain to remove if you do not have a high powered iron because the pill acts as a big heatsink, so my small 30W electronics soldering iron had no hope of providing enough heat to melt the solder and wick it away. I had to bring out my behemoth 100W plumber's iron (with a tip that is 3/4" wide) to get the job done.

The driver IC is a Zetex C310 IC. I changed the sense resistor to increase the drive current from 0.4A to 0.6A, upping power output from 1W to 1.5W. The measured efficiency is 90%, which is very good for a boost converter.
 
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