Yeah I didn’t read that right… Working 12 hour shifts starting at 4am messes with you a bit… The shaved Dome won’t eliminate the dark spot but may help due to focusing the hotspot
:bigsmile: :bigsmile:
I’ll look if I’ve a razor or sharp knife that is capable of cutting the dome. Otherwise I’ll leave it as it is now.
Thnx
I resoldered the led connections and put some new tape on it, now its working as it should.
Dont have a razorblade or any other sharp knife for cutting the dome so I’ll leave it. Its much better than before so im happy with the results :).
You might try to sand the dome carefully with fine grit sandpaper to make it opaque, I had this idea a while ago but have not tried it. I expect that the hotspot widens a bit and the dark spot more or less gone.
Morning. Can anyone specify what ‘shaving the dome’ means? Is it simply cutting the dome flat instead of de-doming? Is it shaved into a particular shape? Thanks
EDIT: Got an answer. How to shave the XHP70 dome. https://www.youtube.com/watch?v=HzyNsogaizg&feature=youtu.be
I just tested it for you (and myself), with my test-XHP70 that was still lying around:
before:
After sanding, I ended up using quite rough paper: 180 grit 3M sanding paper (3M paper is the grippiest sandpaper I know, never use a different brand), carefully sanding all sides of the dome, took 10 minutes to get the finish a nice opaque.
Cellotaped the ledboard to a smooth plastic C8 reflector, used an almost drained alkaline 9V block for power
The dreambeam:
How the led looks in the reflector, picture was taken through an audio-cd:
Someone must have tried this before????
Like what happens with dedoming, the opaque dome surface causes a certain amount of light redirected into the die, leading to some light loss, increased surface brightness and tint shift, I don't know how large this effect is, I assume considerably less than with dedoming. (unlike dedoming this does not go together with smaller apparent die size)
Don't know how the dome behaves at high power, I guess it will alright but no guarantees. I may try that sometime.
djozz. Nice. Thanks 
Just a couple days ago I mentioned to someone that we used to sand Luxeon LEDs to get more diffused beams (throw wasn’t priority 10 years ago) and that there is no reason why it wouldn’t work with XHP LEDs. Thanks for proving that it works!
.
That’s a freaking cool idea using a CD to reduce light!
Not mine, it comes from advice on how to watch solar eclipses
Exactly what I was going to ask! lol
Well done dgozz! I have an HP50 in a XTAR TX20,powered by 2 mxjo 18350 batteries.even at a distance of better than 130feet the dark spot in the middle of the beam is still visible. Question, when sanding the dome, ae you using a sanding block? Also how do you deal with the dust caused by sanding? Any comments/help is appreciated. Thanks
Jim
I’d guess that sanding was done by hand and the dust was just washed off the LED with soap and water.
Correct, a small piece of sandpaper, a couch, and and 10 minutes of Zen. The silicon was slippery at first, but after some light rubbing for a while it starts to come off nicely :-) . The dust was blown off and then brushed with a soft brush.
This should work for you. You should just need to put a thin copper shim under your MCPCB.
42mm (D) x 39mm {H} OP Aluminum Reflector for Cree Q5 (1 pcs)
EDIT:
Emitter Hole Diameter: 9.6mm
Might need one of these Convoy C8 reflector sized centering rings?
9.8x2.3mm XM LED plastic insulation fixed position positioner for CREE XHP-50 XM-L XM-L2 5x5mm chip LED
Thanks djozz for trying it out!
It really looks great. If you have to guess how much does the output drops?
I might try that one time.
I might try that too. but my guess is that the drop is not all that much.
Thanks for testing that. I am planning an XHP50 zoomie.
Perhaps if we sanded more of the dome away in a partial dedome the spot would get a bit smaller, but still have no dark spots.
So this weekend I sanded the dome on my XH-P50, it wasn’t that difficult to do.
I didn’t sand as much as djozz did, just so I could test when it was enough.
Not sure what grid I used (already forgot it :P) if I had to guess it was somewhere around 120.
I ended up sanding only the top ‘half’ of the dome (with these XH-P leds, just above those flat spots on the side).
(yeah I know the dome is a little dirty :bigsmile: )
I have to say, the dark spot isn’t 100% gone but it isn’t really noticeable now. I’m happy with the results.
I'm not sure if the dirt will not do any damage when the led is driven hard, dirt pieces may absorb so much heat that they burn into the dome or even cause the silicone to melt/burn (this may be the cause of a burn stain on a XM-L2 dome that I had once)
Don’t worry, I cleaned it :bigsmile:.
I’d love to see before and after beamshots!