So, I bought the xhp70.2 version of the m21e from Simon.
I also bought a sft70 when they came out.
I installed the bare sft70 onto a 5050 footprint 20mm mcpcb.
I then installed the sft70 into the M21e (6volt driver).
when I turned it on in low mode it was ok, as i ramped up I got BLUE light, I quickly shut it off.
curiosity got the best of me, I removed the mcpcb and checked my "reflow" and also my leads when resoldering it back in. Tried it again, I got BLUE output again at top of ramp and then .. smoke and nothing..
I reinstalled the xhp70 and nothing worked.
Simon was nice enough to send me a new driver really quickly (it's a great design by the way, no wires to the switch, it's "all in one" like an Olight baton driver).
I installed the new driver and the original xhp70.2, and everything works totally fine.
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What could of happened ? Is the sft70 12volt? Can it be either 6v / 12v and I used the "wrong" mcpcb for my 6v driver?
I am pretty sure I did not have anything shorting out. It's a pretty straightforward designed light, so I'm pretty sure.
any help would be .. helpful. Lol.
I want to know what lights I AM ABLE TO put the sft70 in, given I don't have any 12v mcpcb's (the ones that have the "interrupted" looking pos/neg pads).
Maybe your SFT-70 was set to accept 6V output, but the driver was giving it 12V?
I’m not familiar with the SFT-70, but I recall the XHP50 and 70 set their input voltage based on how the star is setup. Perhaps the SFT-70 is the same, and it had the wrong star?
Another possibility could be overheating. This could happen if there was insufficient solder under the central heatsink pad on the star.
The driver may be fine, but the emitter is probably toast.
So I don't think it was a mechanical or reflector short, because when I installed the new driver and the xhp70 everything was fine.
the wrong mcpcb star is what I'm wondering was the problem. I am pretty sure all of Simons xhp 50/70 lights are 6volt drivers only.
so maybe the sft70 was put on the wrong mcpcb and was wanting 12v based on the mcpcb but was only getting 6v?
although, maybe I did come up short with enough solder under the led, and that was the problem. The only reason I knew the driver was fried was bc when I put the xhp70 back in, the light still wouldn't work. And before all of this the light worked fine with the same xhp70 led& mcpcb. The light was an hour old when I did all of this lol.
It bothers me that I'm still really confused about the whole 6v & 12v "thing" - does the mcpcb matter? Is it only the driver? Why do some mcpcb's look like this? https://imgur.com/a/JCkGdPZ
and some don't have that "break" in the pos/neg" pads?
why do the back of some leds look like that 7070 mcpcb in the picture above?
In what circumstance do you use each type?
why does it seem only xhp70 have that odd layout mcpcb, but it's the same voltage as the xhp50 and that mcpcb does not have it?
An XHP50/70 is composed of 2 strings of 2 LEDs in series (6V), the two strings are not connected together, they have individual pads. Depending on the wiring on the PCB the two strings can be in parallel (6V) or series 12V (page 27).
The SST/SFT70 is the same, see page 15.
So there are 6V MCPCBs and 12V MCPCBs, and 6V/12V ones configurable with jumpers that can reroute in parallel or series.
Anyhow even if the MCPCB was wired for 12V it shouldn’t have killed the 6V driver.
For 6V, you jump the ‘J’ pad. This effectively is the same as a “3V” or non-split pad mcpcb.
For 12V, you leave the ‘J’ pads open and jump the ‘R1206’ pad. This routes the current across the first 2 dies of the emitter, then loops back around (through the R1206 jumper) to pass through the second series pair of dies.
Summarized. 6V is 2P2S and 12V is 4S.
This is the excerpt from the Cree PDF TheFreeman referenced.
As for what happened to this thing, I’m clueless at the moment.
Awesome. JaredM & thefreeman, thank you for this, and I was really hoping at least one of the two of you would respond. This is helpful, I have screen shotted the pages of the data sheet you referenced thefreeman.
jaredm- that make sense seeing that 6v/12v compatible mcpcb. Jumping the J spots or the other 1206r spot makes sense to me, and the 2s2p or 4s does too. It helps seeing this.
so this anomaly of a burned driver aside,
I have a couple 12v lights that use very standard mcpcbs, like a basic mcpcb that I would use for a xpl-hi . (the Olight M2r series uses these types of mcpcb and so did the thrunite tc15 iirc.
how is that possible? I guess that's where some of my confusion lies, why do some lights need the mcpcb you showed a picture of, JaredM? And other lights just use a "standard" 3v compatible mcpcb?
but, I do understand more now about why the "split pad" mcpcb is used, or more so how it is used.
Also- this makes me think maybe I just shorted out the light in some other way, maybe my reflow of the sft70 to the mcpcb was not as "solid" as I thought it was.
I wonder if the led will be good anymore? It doesn't show any burn marks..
Those lights use XHP35s which has the 4 dies internally connected in 4S, it’s not configurable via the PCB.
Similarly to that, Nichia (B35A, 144A) doesn’t do configurable voltage, but they sell different 6V (”M”) and 12V (”R”) versions, whereas the XHP35 is only made in 4S version.
It probably is okay if not burnt. Can you test with a power supply set at like 5.2V ? Or hack up a USB cable and use a 5v source.
Actually, I have a hypothesis on what could have happened.
If one of the four split pads didn’t make a good solder connection (failed to wet), then all the current would have flowed through half the emitter. This would cause ‘blue’ at half the expected current.
Running the LED at too low a voltage shouldn’t damage the LED. It just wouldn’t light up. So if the LED is configured in series and needs 12v, applying 6v from the driver should not damage it.
However, running the LED at too high a voltage can burn out and destroy the LED.
Also, a poor reflow that leaves a gap between the central heatsink pad and the star can cause an LED to overheat and burn out very quickly.
Another thing you should do is check to see if the driver is ok.
Remove the SFT70 and reinstall the original XHP 70 that came with your host and see if it lights up.
If so, then your driver is fine and the problem is in your SFT70 or its star.
My guess is a poor reflow… That aside, some drivers will fail if powered up with no load connected to them. So, if half of the led was connected and over currented and failed, this would lead to a driver with no load connected. Maybe the cause of the driver failure, if it indeed failed.
i think I have an older 5v power supply.x I'll try that!
and that hypothesis makes sense! I've been a little "Gun shy" lately while flowing leds on mcpcb, as i had some issues using too much solder recently. I could've used too little. I can check that! The blown driver.. who knows?
I did do exactly that- I removed the sft70 and reinstalled the xhp70, and it did Not light up. Neither did a xhp50 6v I had either.. but got a new driver already so it's all good there.
good to know about too low of voltage not damaging it.
i definitely could have. That is possible in my haste at the time. That blue light really got ME heated lol.
One question- if the led has a "split" pad layout but I soldered it into a mcpcb with a "standard" 3v like layout, would that of like "shorted" the led pads so they all "ran at the same time", or so that the led got voltage to both of its 2s at the same time?
Edit: that would make it 6v, wouldnt it? If 2s got power at one time.
