I would like to mod my GT with an XHP70.2, someone can kindly tell me which resistor to replace on the original driver, and possibly which value to use?
Thanks.
You need to replace the 2512 3W resistor with either a .050ohm or .040ohm. The .040 is not officially recommended but it has been working fine in my light for months now.
The biggest issue is the xhp70.2 mcpcb, they are hard to find.
I am trying to talk lumintop into making a batch of them and I think they might do it. Although time will tell for sure.
Tomorrow evening Djozz and I will measure our BLF GT’s in the basement floor of my appartmentblock: we have an indoor beamshot location of up to 45 meters……….
should give us some decent throw numbers indication.
Once you look at the driver it will be clear which one it is. It is the only resistor of that size on the driver. Right now it should say 91 or something on it.
Lexel wrote: “I am working on a CFT-90 driver for GT”.
Hmmmmmm……I think I already know where part of my holiday allowance will go to
Djozz and I did some measurements this evening, at 21, 13 and 8 meters.
Djozz’ light performs quite a lot less less then mine, so we measured only my light at all three distances.
And Djozz has his work cut out to find out what’s wrong with his light. :rage:
Results:
Djozz light: 21 mtr = 832.167Cd
My light at 21 mtr = 1.142.190Cd
Mine at 13 mtr = 1.139.060Cd
Mine at 8 mtr = 1.142.336Cd
(We measured with Djozz’ calibrated Gossen Luxmeter and deducted the ambient light @ 61Cd).
At first I was baffled by the lower readings at higher distances and thought it might have to do with the convergance of the light but I saw others posting
similar results, so……it looks like the BLF GT is already fully focussed at 8 meters.
1.142.336Cd is not bad, not bad at all, but still a little bit lower then I had hoped for.
So, thinking of replacing the led with the latest bin and maybe giving it a little more power as well, say 2,8A instead of 2,5A.
Then again, a custom Lexel driver and a CFT-90 might be really nice as well
Cheers and wishing you all very bright days and nights,
Nico
Driving a XHP70 with just a 0.047 Ohm resistor will be disappointing at 6V
This would result in 5A
Also switching frequency would not be ideal, the diode would be quite close to its limit
I changed the Inductor, MOSFET, capacitors and diode with better parts for higher currents also the switching frequency will be set to a point where the drivers efficiency gets optimal
Also reducing the current sense resistor and lowering the current control voltage divider helps reducing heat
I should get next week the 20-40A synchronous Buck driver boards that I developed for CFT-90 and going to assemble and test the first prototype