So I did some research on this iconic caving lamp.
1st generation
The first generation was introduced on 1999 (I thought it was a lot earlier around mid 80's)
It had 2 light source: a 6v bulb and a 6v halogen bulb.
The light come with one replacement bulb of each type and had a special place to store them.
I could not find data on how many lumens each bulb produced but it was very low.
The halogen bulb could move inside the reflector to change the beam type.
The operation of the light was very simple move the switch up turn on the halogen, move the switch down turn on the regular bulb, switch in the middle - turn of.
While in of mode the switch had a mechanical lock off.
Models:
All generation had few variations: (I don't have all the variations so these pictures are from the internet)
1. Duo - the original headlamp with rubber bands
2. DuoBelt - with longer cable and bigger battery box for 4 C cells to carry on the belt (reduce wight on the head and can keep batteries warm under the closes)
3. Fixo - to mount on a helmet.
4. ATEX - (black color) for hazardous areas (explosives etc.)
5. Explorer - Fixo + Aceto (Carbid lamp) mounts on an EcrinRoc helmet
2nd generation
An upgrade with 5 LEDs was introduced on 2006.
It was a simple PCD with 5 LEDs connected direly instead the old 6v bulb without any driver.
The operation was kept simple (on/off)
The PCB was also sold desperately as an upgrade to the 1st generation
The 5 LEDe output was 40 Lumen for 28 meter and last 65 hours.
The halogen beam was for 100 meters and last 4 hours (no lumen data)
For this version also the locking mechanism for the switch and battery box was made from Aluminum instead of plastic (probably after costumers complained)
I only have the ATEX version for this generation but of course there was also a regular version (and also belt, fixo, explorer...)
3rd generation
An upgrade with 14 LEDs was introduced on 2008.
Petzl kept the old halogen bulb with zoom option but offered an upgrade to the led PCB.
The PCB was a lot more complicated with a regulated current and 3 mode of operation:
Maximum: 34 meters, 110 hours, 67 Lumen
Optimum: 36 meters, 148 hours, (no lumen data)
Economic: 15 meters, 183 hours, (no lumen data)
The halogen (same as before) 100 meters, 4 hours (no lumen data)
I only have the Spelios version for this generation but of course there was also a regular version (and also belt, fixo, ATEX...)
Spelios is the successor of the explorer. 14 led Dou mounted on Elios helmet without Aceto
That is the actual light I am planing to modified since it is already mounted to my favorite helmet :)
4th generation
The last official upgrade by Petzl for the Duo was 1W LED to replace the original Halogen bolb.
since it fits to the same place it also had the zoom option
Unoffiacal generations
Since Petzl stop upgrading the Duo light (they do make some models named DuoZ, DuoS etc. but not related to the original Duo except from the name)
Some very talented cavers start making their own modules to upgrade the Duo.
The most famous is a British lights manufacturer John Biffin who sells them under the name Customduo.
I have 2 of his modules, 1 to replace the Halogen and one with 2 emitters
As you can see the limitation of this modules is heat dissipation so the maximum brightness is around 500 Lumen :(
This post turn out to be A LOT longer than I thought but I think it explains the history of this light and the reason it is impotent to me to keep the tradition and to upgrade this model to the most advanced LED technology.
Hope i didn't bore you too much