BLF GT (preliminary) modding thread

I managed to open my GT head with a leather belt :slight_smile:
I printed out Enderman’s focus checking circles with the 3 square. I have still my friend’s GT too so I checked both. Mine was good for about 1m distance and then started to seem over focused. The 3 square moved to the center. At 7-8m the 3 squares almost completely overlapping each other. That is why I got the biggest numbers at 10m because it was focused around that distence. My friend’s GT was even worse. As we seen in the intensity numbers too. So I need to sand the centering plate thinner. I needed to go to work so tomorrow I will measure centering plate thickness and sand it down a little.

could you take a beamshot before and after sanding the centering plate?

you don’t see it on a beamshot. Maybe with the focusing templates you can see the squares but with naked eye I don’t think so. But I will try to make photos.

I meant a photo that compares hotspot of a stock vs sanded centerpiece

I can try but you will don’t see much I think. These are not huge differences just hunting for the perfection. If I can manage to focus better and make 1100 kcd from my 980 kcd it is not what you can notice in a few meter wall beamshot.

Just tell us if sanding down the centerpiece improves the hotspot at larger distances. Especially if it can remove the corona and make the center brighter.

Sure I will report results :wink:

Thanks!

I have some results! :smiley: My theory was a bit wrong. The centering plastic wasn’t too thick. It was thin. I sanded down from 2,5mm to 2,33mm and it made worse. I only got 874 kcd from the stock 980. So I started placing kapton tape stripes to the bottom and about every 0,1-0,15mm added I reassembled the head and went outside to measure lux at 10, 15, 20, 25m.
Today’s last result was 1100000 cd at 20m with 3,17mm thick centering plastic. This is not the end and I have pics and a lot of numbers. The interesting that as it was getting better the highest number moved to the bigger measuring distances which I think is good because the beam is more parallel and forming the hot spot farther is good. Tomorrow I have a lot to do but I think I will add some more tape under that centering piece and I want to find the best focus setting. And I will post all the pics and numbers when Im done.
Stay tuned!
:smiley:

Interesting, thank you for sharing :slight_smile: :beer:

Very interesting results.

The latest batch of reflectors was made by another company (which is why there was no shipping delay this time). It is possible that the focal length has been changed slightly. It would line up well with the XHP70.2 I built.

I used a 4.25mm centering ring on the first light I built and it had no dark spot but it took almost 5mm to get the same results with the new one.

Plastic shims for under or on top of the centering block. Mine is shimmed at 3mm thick overall, my other GT’s reflector was better so I swapped them. Dark hole in the beam 3.5-4ft. off the wall.

After running about 30 Minutes on Turbo on a sunny afternoon :wink:

I tweaked the focus a little bit but it is still far from perfection. Measured 1.7 Mcd-2.3Mcd.

Regards

Kenjii

Today I went up to 3,42mm centering piece thickness and got 1174500 cd.
but the hot spot started washing out so I think the optimal thickness is between the 3,17mm and 3,42mm. Now I need to sleep so I will try the last steps a few days later when I have more time.

Do you have a donut hole in the beam or not? I hat a visible donut hole when I placed shims under the centering plate. It was visible even at 250m distances

Good info, If you find a perfect thickness I will pass it onto lumintop and see if they can make some updated centering rings.

Anyone else that wants to experiment with this be sure to post your findings as well, the more the better.

Luckily I have my friend’s GT in my hand so I will try focusing that too. That was even worse stock than mine. It only got 894000 cd. Now I have two workdays so I don’t have time for it but after that I will upload all results.

EDIT: I talked another hungarian forum member and he will send me his GT head too to measure it and focus it. So I will have 3 GT focus tests but all 3 is from the late February or early March batch because they all had same tracking movements around few minute differences.

Ok, so these are from the old reflectors, still good information to have.

I spend one morning messing with the center piece of my GT, made it both thinner and thicker, but never got rid of the slight donut hole, and the throw did not get better. I may have to look more precisely, but I first have to replace the ledboard screws with version that do not have a very round head but heads with a straight side, so that the center piece can be positioned exactly and keep the led in focus. But it takes too much time already, I will first wait for a new led to arrive…

I have been testing with my GT using a flat plastic piece placed under the original centering disc. I have cut it with the same shape of Lumintop disk but with a bigger central hole. (Similar to those in the picture of KawiBoy1428) I started with a thickness of 1.10 mm and I have repeated readings sanding it down to 0, 90mm, 0, 70mm and 0.40 mm.

The starting point is 1.203.000Cd using a boiling thinner dedomed XHP35 E4 HD.

Lux readings were taken at 10m. I have no more available length in my house but I will try to measure in the community garage at 15 and 20m this night, when the lights can stay off, without car transit. As it is only an experiment the readings are taken at the start of the light. Therefore, No ANSI

These are my results at 10m.

- 1.10mm: Ugly spot with blurred edges and a very marked black hole up to 5m. I did not mensure. It was obvious that the result would be bad.

- 0,90mm: Nicer beam profile with a more definite spot. The black hole from 4-5m onwards was replaced by a central area that, although irregular, was more illuminated than the rest of the spot. 1.092.000Cd.

- 0,70mm: More defined spot. Illuminated area in the center of the spot is regular. 1.229.000Cd.

- 0,40mm: Perfect and well defined spot. 1.299.000Cd.

I finished the sanding because I hurt my fingertip with the sandpaper. :weary:

I received my GT on February 23rd. I don’t know the date of manufacture

My luxmeter is a cheap LX1010B. I have hope that when I buy in the future a better luxmeter the results will improve.