Modding the U2 with Seoul

I know this has been done before but a few comments of my own:
-Despite opening a U2 head before with a little heat and a lot of force from two locking-pliers and rawhide padding, I COULDN'T do it on my new U2 head.
So I put it in the freezer for 30 mins then added a few drops of acetone to the groove over the threads and it came free (with a lot of force!). The grnamin YouTube video is a must-see.

-The LED sits between two grooved projections on an anodized aluminium heat sink that is gently stuck to the electronics module with what looks like Arctic Silver 5. The old Lux V fell off this when desoldered.

-Test fitting showed that the P4 abuts the back of the reflector and so a small amount was knocked off the reflector with a Dremel to bring the LED closer to focus. The material comes off the extra aluminium backing the reflector, not off the silvered area at all.Edit- the flat back of the reflector also pushes down on the solder on the LED contacts if you heap it up at all, so keep it flat.

-I still needed more room so I took away a small amount of material from under the old LED (between the heatsink projections).

-The SSC fits perfectly in that space. Arctic Silver epoxied in place.

The output is a little more throwy than the stock, but seems to have more total output than even my WXOS-modded unit. Beamshots to appear on icudoc.com tonight. Runs on one 18650 noticeably brighter than the WXOS on two CR123As. Edit- some mod photos on the website. Beamshots laterish.

-I have done 10 or so mods- this is the hardest because of difficulty opening the head. Otherwise the Dremeling is slow and steady not ultra-high precision, and the rest is easy to get good alignment. I am pleased with the outcome.

Did you stick another resistor in there, or another driver board? I thought the U2's driver hit the LED with 6.0v or higher (Vf of a LuxV), which seems like a recipe for a Seoul friode unless I'm missing something...

Good point well made.
I don't know how the circuit functions but the head barely gets warm with prolonged use so I am happy the SSC P4 LED is comfy in there. If it is constant current and well-designed maybe the LED Vf has little effect and so is truely safe? I just don't know. Others have done this and used them longer so I guess there is more data out there.....

Is 6 levels brightness still funtioning ?

Yep- 6 levels firing away! The low is not much different to my eyes, but brightness jumps up from about Level 3 on.....

I suspected a direct drive mode in at least in level 6, you would better avoid 2x 3V configuration, and stick with 18650.


Do you still see the difference in brightness in between 4-5-6 ? If level 6 = 100%, how much for level 5,4,3,2,1 ?

OK this is just by eyeball, 'though:
5-80%
4-50%
3-40%
2-10%
1-3%
There are published drive currents out there, and maybe outputs as well but these are what I see, as it were. The difference between 3 and 4 is small, 2 and 3 is large.

Sable said:

Did you stick another resistor in there, or another driver board? I thought the U2's driver hit the LED with 6.0v or higher (Vf of a LuxV), which seems like a recipe for a Seoul friode unless I'm missing something...

Click to expand...

The stock U2 does not use a resistor for limiting the current.
It's current regulated the electronics can handle Vf variations as long as it can keep the regulation. If it's boost only, then you might encounter problems.

I tested U2 with cree before, but with 6V configuration. During that split second flash, the current was over 2.4 Amps at the emittor !

Will try again with 3.9V & Seoul in the next day.

The U2 should work with an SSC-P4 and Li-Ion. The LED ideally would have a higher Vf or you will probably not get the lower levels since the converter is strictly boost only and if Vin is higher than Vf then all bets are off.

ICUDoc, PM sent with stupid questions and if you could read it, PLEASE??? I would appreciate it!


Thank you,
Ken

CM
I just don't think that the convertor could possibly be boost only. The setup I have clearly generates the lower levels just fine, so there must be some limiting / regulation going on. The output on high looks similar in total output to other SSC-P4 LEDs I have run at about 1 amp. On low, I have no comparisons, just my estimates above.
Kenster- there are no stupid questions. I hope I have no stupid answers!!!

ICUDoc said:

CM

Kenster- there are no stupid questions. I hope I have no stupid answers!!!

Click to expand...

ICUDoc, thank you very much for the info and help!


And thanks for covering for me on the stupid question part.


Ken

ICUDoc said:

CM
I just don't think that the convertor could possibly be boost only. The setup I have clearly generates the lower levels just fine, so there must be some limiting / regulation going on. The output on high looks similar in total output to other SSC-P4 LEDs I have run at about 1 amp. On low, I have no comparisons, just my estimates above.
Kenster- there are no stupid questions. I hope I have no stupid answers!!!

Click to expand...

I'm starting to get this deja vu feeling. Are you running off 2x123? If so, then it appears that it's a buck/boost setup.

No CM I am running the modded U2 off an 18650. A difficult mod but I love the result.

Can you try it with 2x123?

I will try tonight Sydney time.

OK, so tonight Sydney time....
Off a power supply set to 6volts the U2 drew 230mA on level 1, increasing to 1.4 amps at level 3, at which point I chickened out.
It drew about an amp off 4.1volts on level 6.
So I will run it off the 18650 only, which is fine and gives BUCKETS of output.
Given this I wouldn't even try 2 CR123As.
Hope this helps, CM.

ICUDoc said:

OK, so tonight Sydney time....
Off a power supply set to 6volts the U2 drew 230mA on level 1, increasing to 1.4 amps at level 3, at which point I chickened out.
It drew about an amp off 4.1volts on level 6.
So I will run it off the 18650 only, which is fine and gives BUCKETS of output.
Given this I wouldn't even try 2 CR123As.
Hope this helps, CM.

Click to expand...

I didn't realize you had a power supply

Here's a test that I would do. Set power supply to 3V. Connect to U2 and measure current and record. Increase voltage 0.1V and then read current and record. Keep repeating. Current should steadily decrease as you approach approximately Vf. If current starts to rise then circuit is not buck boost--it is boost only. If current continues to drop monotonically as you get to 6V, then the circuit is buck boost. It would be very instructive to post a graph of Vin (from power supply) vs. current. If you have trouble doing that, send me your results and I will post the graph on your behalf. Thanks--CM

I tried taking my U2's head apart just ended up with a few scratches, wa susin g2 brand new 10 inch vice grips, leather failed (not thick cowhide) and so did 7 layers of bycicle innertube, but I have to live with it