Need Advice - SFT40 Emitter Swap - EA01s (fail, so far)

also, if i have one of the LED"s polarity turned opposite would that cause this problem? the one thing about the SFT40 is i cannot tell at all which side is + and which is - ... There are no dots, lines, or any visual queues like there are on almost all other LED"s i've worked with..

I haven’t worked with these LED’s yet, but is there any markings on the pads underneath to denote polarity? Failing that, looking at your pictures there’s a cut out in the very corner of each LED. I bet that marks the anode or cathode.

With regards to the solder bridge, before you reflow the LEDs check for continuity between the positive and the underside and the negative and the underside of the MCPCB. This should confirm you have a bridge. If you have, remove each one and check. If you have a fine point for your soldering iron, you should be able to remove it with that. Then try your reflow again. If you have excess, tapping each LED should squeeze out any excess and you’ll end up with little balls to the sides of the pads. Let us know your results!

Do not rule out a possible short between trace and core because of the sanding work you have done on the PCB.

Ok thank you for this info! so you said:

If i have a solder bridge when checking pos/underside of mcpcb and neg/underside, what will happen? the LED"s will light up? or the DMM will react? Sorry, i do understand what you mean by checking the continuity of the pos/underside and neg/underside, but what will i see if there is a solder bridge?

Thanks! i will definitely let you all know!

so i hope i didn't create a short, but i will say - all of the problems were happening (the constant ON, direct drive) before i sanded anything, at all. i only sanded because in my limited lack of knowledge thought maybe the problem was happening because the edge of the mcpcb was making contact with the inside of the flashlight head so i made the diameter smaller to eliminate contact. I've come to find out that didn't matter because inside of the head is cleanly anodized (except for the shelf, of course). So my problem existed before my sanding, but now i may of created another problem of course by creating a short. let's hope not! if so, anyone have the Mateminco rep's contact info? LOL.. lets i hope i can fix this though, and I dont need a new mcpcb...

Basically, there shouldn’t be continuity. So if your multimeter beeps (or however your multimeter registers continuity) then you know there’s a problem.

ahh, got it! yup, that makes sense! lol...

(we really need a crazy eye emoji, because half the time i ask a question i could use it lol)

Being a cautious person I vote the same as the majority: there is a short (somewhere) between the black lead and the body. I would check every point where that can happen.
1 Starting at the (downside) of the lead itself. A number of times the insulation of the black lead was torn against a sharp edge on the leadboard.
2 Check if the leadboard has (a bit) “room to move” in all directions. Thus preventing that a sharp edge on the ledboard can touch the body because of damaged ano.
3 Et cetera, just work your way up to the leads themselves.

There’s a notch on one vertex. You can see it in your pictures. This is the anode side. I think you got it right.

The SFT-40 has two pads, anode and large cathod. So, on a MCPCB for the SST-40, you bridged cathod and copper core, or am I completely mistaken here?

Alright, I Finally got back to it this morning- and I believe you folks were right! It's working!

So I removed the mcpcb, and started by checking the heat shrink I put on the negative lead, it was intact and covering it fine.

I then threw the mcpcb back on the hot plate and got to cookin' ! I removed all 4 leds, checked to make sure there was no solder smeared between the (3) pads for each led (main, pos, neg) and also checked the back of each of my sft40's. Everything look good so I reinstalled the sft40's to the board, giving the the vertical bump test for excess solder as well as the horizontal bump test to make sure there was enough solder for that famous "bounce back" (as a side note, i am 90% sure this is where I went wrong initially, I am pretty sure I did the vertical push test in the wrong direction hence smearing solder paste under the pad of the LED). After the mcpcb cooled a few minutes I reinstalled into the head of the light, said my prayers, and voila! Here's the picture for proof.

Next I may be sanding down the thickness of the centering rings to dial in the beam better, but I want to see it tonight first before messing with it.

also, I will be changing the name of the thread so it looks more like a mod thread and less like a cry for help lol. I'll make a note in the OP regarding my trials and tribulations though.

thank you again everyone for all of your help. This was another of many learning lessons for me and I know it won't be the last. But I will say I was close to giving up and just seeing if someone wanted to buy the thing for pennies on the dollar. Now I can't wait for the beam shot! Thanks again!

henk & Unheard- thank you for the info! It helped, everyone's helped and I think everyone collectively was spot on! I love this place

Edit (post#22) - I will just start a new thread for "documenting" the mod, I just reread everything and it doesn't make sense to alter this thread and turn it into the mod thread.

I have a T-12 solder iron on its way with flux paste syringes, solder, resin core solder and precision tweezers. You give me inspiration Artie, I just want to do simple mods like you. Pretty awesome bunch of fellers here to help where they can.

Good to see you got it fixed!

How is the beam of the SFT40’s in the EA2 ?

That is SO AWESOME to hear! I know i can ask some mindless questions on here, but everyone is generally really nice to me about it, and i am having a lot of fun swapping these emitters out and all that.

Your incoming setup sounds perfect! its exactly what i started with! i also bought some Kester liquid flux (#951 & #186), it helps the solder flow and "grab" better on harder to solder parts (i used to solder wire to magnets today for charging setup).

The next suggestion i would make - check out Simon's Convoy store on AliXpress for emitters, and VERY Important - centering rings. i had my whole soldering station in and ready to go with some emitters i wanted to swap when i started and realized i needed centering rings! you can make them from pieces of plastic (cutting them, but if you 3D print thats the best!), i've done it, but Simon sells like 10-15 different sizes that have different reflector opening sizes and emitter hole sizes, i grabbed one of every size he sells. i keep them in a bag, they are very helpful to have! i will often drill them out and shape them if they dont fit what i'm working on.

Plus, i know theres a lot of places to buy emitter (MtnE, Kaidoman, and others) but if i am looking for a specific LED, i will ask Simon and he has actually brought an LED in for me. Really Cool, i buy most of my LED's from him. the Blue CSLNM1 osram was brought into his store on my request 6 months ago lol (im sure he would've brought it in anyway eventually).

good luck! Im glad to hear i have in some way broke down the intimidating first step to doing simple mods! Hell, if i can do it you definitely can lol. message me anytime if you have questions. or, do what i do, bother EVERYONE with a new thread LOL.

Thanks! Its the EA01s, the quad reflector one. The beam i havent been able to really see yet, but there is a definite "flower petal" shape and a TIGHT hot spot! Cant wait for tonight!

Also, a side note.. i bought a lux meter to measure throw like 3 months ago and have been to overwhelmed by it to even try using it.. I wanted to measure the candela on this EA01s before i swapped the LED's but i didnt. Im going to try and figure it out to measure the candela on this light now with the sft40.. The problem is i tried looking up a video on youtube to help show me how to use the damn lux meter and EVERY video was how to use the thing to measure lumens for your pot growing bulbs! lol! didn't help me bc none of those guys are measuring the throw of their grow lamps! lol.. ill try and figure it out..

Oh! i almost forgot -unless you already have one, buy a Hot Plate. if you search "hot plate" on amazon there will be 1000 options. i bought the cheapest one on there for $18 USD, it works perfectly fine. you need to go as LOW heat as possible or your mcpcb stickers will turn brown lol, but it does the job and was pretty cheap. it helps with getting the LEDs off of the Mcpcb's of course. there are other ways, but i've gotten my $18 out of that thing 10 times over.

Measuring throw is quite easy, just keep in mind that the longer the distance will be more accurate, (I always use 5m since that just fits inside my hobby garage)
Try to find the spot in the hotspot that gives the highest number and calculate that with Rapidtables

Candela to meters = SQRT (Cd/0.25)

Matt Smith (forum member "vestureofblood") has two YouTube videos regarding the use a digital light meter for distance estimation and lumen output:

1) How to measure flashlight beam distance!

2) DIY Lumen Measuring Device. Integrating Sphere, and Lumen Tube


The link below is to a blog post by forum member "dave1010" about "Converting Candela to Throw" including the definition for "ANSI measurement of throw" with a comparison to the light from a full moon and the practical expectations of that.

https://davestechreviews.com/2020/05/26/converting-candela-to-throw/

Yokiamy, thank you so much for the website to give me the calculations! i just saw this unfortunately, and the sun is coming up here so i wont be doing this until tonight now. but that is fine, i have some time this morning to try and adjust the reflector height/opening.

i was surprised last night and early this morning when i used the light that the beam distance was not throwing far at all (meaning i have markers in my area that i compare lights with like trees at 100, 200, 300 meters). but it made me realize i really need to adjust the reflector height to get the beam quality and throw dialed in. i will hopefully have some numbers to share tonight / tomorrow morning. Thanks again!