The PT EOS is a reliable and durable headlamp with many great features. However there are a few areas where it can be improved upon, namely the optic and the LED.
The PT EOS produces a beam of light by channeling the output of the LED through an optic. This is adequate for most users, however the produced beam lacks sidespill. In the case of a headlamp sidespill is especially useful as it allows you to light up a larger area for close up work. By removing the optic in favor of a reflector we are able to produce a nice smooth beam with lots of sidespill while still retaining a good central hotspot.
The other item we can improve upon is the LED. The PT EOS comes with a Luxeon I LED which produces nice bright output, especially for a headlamp. However this LED is somewhat outdated and more recent LEDs can now produce twice the amount of lumens at the same current draw. This is quite an improvement.
By modifying these two things we are able to make a great headlamp even better. The modification is not difficult and the results are spectacular; well worth the effort put into it.
-Drill with small drill bit
-Soldering Iron & Solder
The first step is gaining access to the circuit board & LED assembly.
Using a screwdriver, loosen the screw on the back of the headlamp to gain access to the battery compartment. Remove the batteries.
You will now need to seperate the battery holder from the headlamp housing.
The battery holder is secured to the housing using two rivets, one on each side. These are visible once you have removed the batteries.
Using a drill with a small drill bit, drill into each rivet until you are able to pull the battery holder from the headlamp by using your fingers.
In the following picture I have drilled out the rivets and am seperating the battery holder from the headlamp:
After you have the battery holder removed, you will see that on the other side of it is mounted the circuit board and LED/optic assembly:
The optic and "optic holder" can be removed using only your hands to allow access to the LED:
The "star" that the LED is mounted on seems to be superglued to the PCB, but I was able to seperate it fairly easily by just pulling up on it with my fingers:
Now we have access to everything and can begin our modifications.
To remove the old LED you must de-solder the red and black wires from the + and - contacts on the star. You can also take the easy route and just cut the wires at the star.
Once the old star is detached, set it aside. It should still be a good and functional LED and you never know if you may use it on a project some day.
Now take your Seoul LED and solder the red(+) and black(+) wires to the contacts marked + and - respectively on the star. Pay special attention to the two notches on the bottom of the optic holder to assure that you are soldering the wires to the star in such a way that they will align with these notches when the optic holder is installed. If you do not do this correctly the wires will keep the optic holder from being able to be flush with the star.
Once you have finished it will look like this:
Now we are ready to begin installing our new reflector.
Basically the Fenix reflector will fit perfectly and securely into the stock optic holder with minimal changes. The first modification you need to make for the reflector to drop in is to file or dremel down the vertical ridges inside the optic holder. You will also want to remove the plastic that connects from side to side across the bottom of the optic holder. This will allow the new reflector will come down all the way on top of the LED and focus properly. I used a pair of scissors for this task. Pay special attention here and make sure it is not possible for your reflector to touch the solder blobs on the star, causing it to short. This will only be an issue if your solder blobs are too tall.
After you have the reflector inside the optic holder you are ready to secure everything together, but there is one more issue to address.
In stock form the PT EOS has a thermal sensor behind the star that detects when the LED is running too hot and cuts down the current to keep it from overheating. Once you install the Seoul star you are left with a gap between the star and the thermal sensor unless you replace the blob that is on the bottom of the original star.
Keep in mind the Seoul LED is more efficient and runs much cooler than the Luxeon III in the headlamp originally. I did not attempt to connect the star to the thermal sensor and I have run it for extended periods of time with no ill effects. It is quite possible that with this new cooler-running LED and relatively low current output of the EOS driver(~300ma on high) there is no additional heat management necessary.
However, it would definitely not cause any harm to use some sort of heat transfer material on the bottom of the new star thus connecting it to the thermal sensor in the same fashion as the stock star. I have also heard of people sanding down and gluing pennies to the back of the star to act as sort of a heatsink, which I would recommend as a simple way to help dissipate some excess heat.
We now move on to assembly...
Install the optic holder with optic over the LED:
Now simply put the circuit board/battery assembly back into the headlamp housing. If you drilled out the rivets a little too far, it may be a good idea to put a drop of super glue in each rivet to make sure everything stays secure.
View from the front with everything installed:
Now install the batteries and hit the power button! You should be presented with something like this:
A nice, bright, smooth beam with lots of spill... Enjoy!
---------------------------------------------------------------------------------------------------------------------------------------------------- *********** UPDATE 11/2/07 ************
The Fenix reflectors originally used in this mod are no longer available. See the following post for more information: http://www.candlepowerforums.com/vb/...&postcount=159
The Khatod 17mm (Which I also have) is also a good choice but I would prefer the fenix reflector over it. First, the khatod doesn't fit as well as the fenix. It is a little too short so you would have to put something behind the LED to push the whole assembly towards the lens. Perhaps this is where you could put in 1 or 2 pennies behind the star and not have to remove the plastic piece originally behind the star. Also while the circumference is the same(I think the khatod is actually very slightly smaller), the Khatod is tapered and the fenix reflector is not. I found with the khatod it would not hold its position reliably inside the optics holder. I may have filed my holder a little too much for the khatod to fit snugly, but I'm sure that I have could fixed this and made it stay with some superglue. Also the fenix reflector is aluminum whereas the khathod is plastic... the fenix reflector may actually help with some heat transfer from the LED (even though it's not in contact with the slug side) because of its close proximity.
Either way you could interchange these reflectors without much extra work. I still have my khathod and may use it if I decide to mod another EOS. I would still recommend the fenix reflector though because it's as if it was *made* to go in the EOS.
The khatod reflector I have is smooth, so I can't help you there =)
You can always sputter a smooth reflector yourself and make it as floody as you want. I did this to a maglite reflector once and overdid it a bit, it was a complete flood light... not exactly what I was looking for in this case.
If you have the Khathod stippled reflector, I would be curious to see if it evens out the spill. You'd lose some throw, but perhaps it would make for awesome bright flood.
It certainly does. I have the stippled Khatod in my EOS, and there really is no "hotspot" to speak of. It's all flood, just brighter in the center. I will try to get a beamshot and post it here.
My Khatod reflector fit perfectly between the lens and led after I epoxied a penny--filed smooth on the epoxied side--to the back of the star. No optic holder needed--the pressure will hold it in place.
The other item we can improve upon is the LED. The PT EOS comes with a Luxeon III LED which produces nice bright output, especially for a headlamp. However this LED is somewhat outdated and more recent LEDs can now produce twice the amount of lumens at the same current draw. This is quite an improvement.
I believe that the EOS comes with a Lux I (at least mine did) which means that the drive currents are set for a Lux I and not a Lux III, but this just means that the Seoul will be driven at close to spec rather that overdriven. My high mode runs ~300mA, I dont remember the middle and low was around ~70mA or so. I used the Khatod 17 but added a copper sheet to the back that also makes contact with the thermistor to monitor the heat.
Overall though very easy mod with great results. I think it is definitely worth the ~$15 upgrade.
Anybody know what range of input voltage the regulator on the EOS can handle?
Looking to add an external battery pack and want to know my options.
Originally Posted by chevrofreak e-mail to Princeton Tec
Can the Eos run on lithium cells, or is the combined initial voltage higher than the maximum input voltage of the regulator? If not, what is the maximum input voltage for the regulator?
Originally Posted by reply from Jay Harrington of Princeton Tec
You can use lithium batteries with the Eos light. We have seen the circuitry handle as much as 7 volts, however if the board is exposed to anything more than 4.5 the warranty will be void.
I'd say that anything from 3v to 7v would be acceptable, but at 3v you will probably only get the lower levels running at full power. The PT EOS circuit does very well on a single Li-Ion, such as an 18650.
I used a cree star (before the seouls were available) and used a drilled out, filed down IMS17. Just recently re-used the optic holder to hold the star on and added a diffusion film. Works quite well. The beam would probably be smoother with a seoul, but I'm pretty happy.
Will have to check out a Zebralight when they come out...
jar3ds, what do you mean the cree stars aren't as good?
I like the PT Eos as a headlamp so bought another as a bike (front) lamp - will stick a CREE in this one to compare.
Still think the stock optic is quite good (fairly similar to a smooth reflector) but a stippled reflector certainly gives much more flood / diffused beam. I have got a variety of reflectors to try but the stock one is zero cost and a perfect fit - so you can do the upgrade for about US$8 (i.e. just the cost of the star).
Nice writeup and pics tibim, thanks for taking the time to detail the steps.
Modded another EOS with P4 and wanted to share a little tweak to get rid of a rattling Khatod 17mm reflector that was driving me nuts! Used a thick rubber band from supermarket produce as a sleeve to grip the reflector inside the holder, filling up the gap and eliminating all movement. Practically invisible when completed and this way you won't risk damaging the silicone lens by crazy gluing the reflector to P4 shoulder.
Also made a thin slit on the lower left and upper right optic mounting tabs with a razor blade, allowing easier removal of the black optic-reflector holder. Sometimes these tabs are really stubborn to get off the 4 grey posts, so if you slit them before removing the stock LUX and slide a razor under the star you'll reduce the risk of breaking the fragile glass thermal sensor.
Plus now you're all set for the next generation LED whatever that is and whenever it's available
My guess (which is just that since I have not done this mod myself) would be that an SSC P4 U bin would be about 60 lumens on High in the EOS. I figure my R bin LuxI light is 32 lumens on high, so just about double that for the Seoul.