Thanks for all the input fellas. Had me very confused and annoyed for a while there.
Due to doubting the 18650ās I have I grabbed a spare 3s LIPO which was sitting about 11.9v , not a full charge but has massive discharge ability. I soldered it up to the old driver I removed from the light (the one with the replacement FET). I again tried to fire up the replacement XHP70 and again it only achieved a very low level of light. This suggested to me the batteries are not the issue, and made me question again the LED as you suggested Texas_Ace.
So I dug around in the spare parts box and came up with a spare 12v MT-G2 just lying around. I wired it up to the driver on the bench, added a heat sink, plugged in the 3s LIPO (around 12v) and ā¦. boom. Ramping mode goes up and up and up way past the dim brightness achieved on my XHP70ās.
I think this is finally solvedā¦ I should have listened to you from the beginning Texas_Ace. It also makes sense to me now with the relacement LED going super bright for a fraction of a second and then reverting to super dim mode. I really didnāt think it would have overheated and fried in that fraction of a second. Iāll have to chalk it up to experience.
I guess Iāll have to speak to Lumintop and try to get another emitter. They were so slow getting me the driver Iām really not looking forward to waiting another 2 months for a replacement emitterā¦
I hope my next update is with a new emitter and the light finally working again.
Thanks again everyone for your input. Hopefully the headaches are now over.
Wow, I didnāt know this. Iām gonna have to add it to my mental troubleshooting list.
So too much heat or current (only on 70.2 or other leds?) can cause it to function normally, but only up to a certain brightness level, then it just stops there?
Already on an MCPCB. I just squashed it down into the thermal paste left after removing the original MCPCB and emitter, I didnāt screw it down. Which would explain why it died in a fraction of a second of full blast.
Having had a little practice reflowing that FET, now Iām thinking Iām probably able to reflow my own LEDās now.
Not a skill I was planning on acquiring but I guess it will be useful ā¦ haha. Iām an idiot.
Oh, so you didnāt have any pressure pushing the mcpcb onto the flashlight shelf. Yeah, it wonāt last long like that. Normally the reflector/centering ring presses it down nice and uniform around the led.
The screws are for anti-rotation. They might work decent for heat transfer, but I wouldnāt trust full power to them. Not with a FET driver and a 70.2.
Over heating explains the 2nd led going bad. I wonder why the first one went bad? Maybe itās reflow onto the mcpcb was not so good. The middle pad of the xhp70/70.2 is just for heat transfer. If they didnāt have enough solder there it may not have transferred the heat quick enough.
Reflowing the emitter is not too hard. You just need something to hold the mcpcb while you blow the hot air up from the bottom. I hold the hot air gun between my legs and hold the mcpcb with some pliers. I raise and lower the mcpcb to change the temperature. My free hand can use tweezers to remove the led.
Then I use my solder iron to remove the old solder and apply new solder. Then you heat it up again over a minute or two with the new led sitting on top of the solder and a dab of extra flux. This will preheat the new led slowly avoiding thermal shock. Once the solder goes liquid I make sure itās centered and push it down so any excess solder comes out the sides. Then remove from heat and let it solidify.
It can happen with any LED I think, I have seen it with several brands and models thus far.
Not sure on the exact cause but I am guessing the LED just fries itself internally and after that the internal āresistanceā is such that only a small amount of light can be made. I have noticed the Vf increases drastically on LEDās that have this issue.
Isnāt cutter in AU? I think you could get a replacement LED form them that is better then what lumintop uses much easier. They have good prices as well if you live in AU and donāt have to pay the shipping.
But then we wouldnāt have had this wonderful adventure together now would we?
I tried looking for an au seller for an led but came up with nothing particularly good. I just ordered a couple more from mntnelectronics. And I asked lumintop if I could have another on an mcpcb just incase I bugger it up with the reflowā¦ā¦ covering all bases. Already spent silly $ why stop nowā¦
Great! Thanks!
Did you have trouble opening the head? I havenāt tried yetā¦
Are 8 cells recommended or does it work the same on 4? - iāve got a choice of 35E (actually in my GT) or 30Qsā¦ Iām assuming 4 is enough to power a single 70.2?
The head was kinda tight, not too bad. I used a rubber strap oil filter remover tool to unscrew the head.
On 4 cellās 30Qs are recommended due to high amp draw (for high power-on lumens) Should work fine, but lower runtimes obviously.
On 8 cells 35Es will be fine.
I removed the switch cover so I could clamp it in a vise. Pieces of wood with a depression for the switch will also work. I found that loosening the upper head from the lower head removes tension on the bezel rubber seal which makes the bezel a bit easier to unscrew.
I had to use a lot of force and slowly unscrew the pieces. They are tight.
