Here's a 4000K LHP73B installed on a modified Convoy 20mm DTP MCPCB, running on a 6V/5A boost driver intended for an XHP70.3. I really like this setup, because it has much nicer tint than the 70.3, zero angular tint shift, the same or even a little bit more output at the same drive current, and runs just as cool. I was inspired by this amazing post to take the plunge.
I bought this light with an XHP70.3 R70 4000K emitter, because it gave me a relatively lightweight 3500ish lumens, and I kept reading that Simon's 4000K R70 bin of the 70.3 had a nice tint. Well, the beam looked like Mountain Dew and I absolutely hated the angular tint shift. I'm starting to wonder if the current-production R70 4000K 70.3s are all crappy tint, because my new L35 2.0 4000K that I bought in February also had a nasty piss yellow beam too. I swapped a 5000K R70 70.3 from Simon into that one. The 5000K has MUCH MUCH nicer tint than the 4000K, but still has some angular tint shift. I can live with it in the L35v2. This light has a much more pleasant beam and is now getting much more use as a result.
The MCPCB mod involves splitting the positive and negative solder pads down the middle (along with the rest of the traces connected to them), to match the pads on the back of the 73B. Then you connect the driver positive to one of the MCPCB positive terminals, then the negative of *that side* to the positive of the *other side*, then the negative of the other side to the driver negative. The 3V forward voltage of each half of the 73B adds in series, giving you a forward voltage of 6V.
Since the driver is providing 5A of max current at 6V, the 30W of power dissipated in the emitter is the same as if you drove it at 10A with 3V (P = i * V, Ohm's Law). In other words, this light on turbo drives the emitter as hard as the 2C turbo1 mode on the M21K.
Mountain Electronics makes a DTP MCPCB intended to run the XHP70.3 at 12V, which you could in theory use to run the 73B at 6V. However, I have some of them, and opted not to use them for this project because I just don't think the thin intermediate trace is capable of carrying 5A or more of current.
by calvinistgrindcore
1 Comment
Very nice mod! I’ve done the same MCPCB mod to run the LHP73B in a 9V grow light (with a big fat high power resistor to fill the remaining 3V).
I keep recommending the LHP73B over the XHP70.3 because of much better tint, especially angular tint uniformity. Good to see this observation made independently by someone else!
What’s your impression of how throw compare between the 70.3 and LHP73B? My hunch is that the LHP73B might throw equally well/better at the same power, despite a larger emitting area, due to the absence of sideways light leakage through the transparent silicone.