want to swap white LEDs for Red LEDs for a Fenix HP25. need help

Hi Guys,

Im new to this forum and not an expert on electronics but have a small amount of knowledge and some experience with a soldering iron haha.

I have a redundant Fenix HP25 headlamp that i would like to swap out the white leds for red leds, probably both or just one, not sure yet.

i have dissembled the headlamp and have got to to the LED chip that sits on a copper disk about 17mm in diameter, so what is the best way to replace it?

do i try to source out a red led that is alright on a similar disk or do i try to remove the type led chip? do i need to reduce the voltage and current and if so, what is the best way to do it?


Thanks for your help,

Simon

simonness said:

........i have dissembled the headlamp and have got to to the LED chip that sits on a copper disk about 17mm in diameter, so what is the best way to replace it?

do i try to source out a red led that is alright on a similar disk or do i try to remove the type led chip? do i need to reduce the voltage and current and if so, what is the best way to do it?

Thanks for your help,

Simon

Click to expand...

The easiest way is to find a red LED already soldered on a 17mm disk. If not then you need to get familiar with re-flowing an LED emitter onto the existing disk. I've done it a couple of times with XP-G2. It's a little tricky. You can do a google search on how to do that. I used a heat gun (no solder iron). The HP25 uses XP-E LEDs, so if you are going to reflow another LED onto the same disk it will also have to be XP-E or XP-E2. I noticed Mouser.com has some XP-E2 red leds that are in the highest flux bin for red in the mid $2 area.

I don't think you will have to adjust the current or voltage if you stay with the same family of LED. Look up Cree's data sheet for the XP-E or XP-E2. Maximum current rating on the red is the same as the white. The red led has a slightly lower Vf but that shouldn't matter if the driver electronics are current regulated which I believe they are. The red will definitely put out less lumens than the white.

Hope that helps. I haven't changed out an XP-E LED......just XP-G to XP-G2 and the XP-E is a little smaller so maybe just slightly more tedious. If serious about trying this I think doing some research on YouTube would help. I use a heat gun with the 17mm disk held by one of those helping hands vice that has the alligator clips and place that about 1" above the heat gun nozzle. I find about 20 seconds at max heat is about right. I just watch for the solder to oooze out in a molten way to know I've applied enough heat. If there is too much solder it will short. If not enough, it won't make electrical contact. You need to test the disk with a multi meter in "diode" mode to verify continuity after you're done. Also you need to remember which wire is the (+) and which is the (-) on the disk so that you get the new LED on correctly and not backwards. You can get the polarity of the LED from the data sheet.

Maybe its possible to purchase a 17mm disk by itself without taking the white LED off of your original and that way you can practice without destroying the original in case this doesn't work out too well.

Thank you for your very informative reply,

I have looked into reflowing an LED and am happy to give it ago as i have all the required tools for the task, i was just worried about the voltage of a Red LED being lower than a White LED but if you think it will be ok then ill go ahead to swap it out and will report back once i have finished.

I will be away for work for awhile so i wont be able to do it until mid-end of June.

Thank you.

Ive found some 20mm led star chips,

is it possible to just trim them down to 17mm ?

thanks