Convoy 3x21A SFT-40 6500K first impressions, info, mods

LED Flashlights – General Info 21700 Flashlights
2

I started on the mods. First added 22 AWG spring bypasses:

Then some minor changes to lessen resistance for the screws for mounting the spring PCB board. Sanded off the anodizing to make contact with the conductive surface of the PCB:

Replaced steel screws with brass ones, and NO-OX-ID treatment:

Couldn't measure any noticeable difference in output. With the stock driver, the batteries were not a bottleneck, but with a direct FET based driver replacement, these mods will all help. Was hoping I could keep the charging in tact but there's too many interconnected singles - I counted 3 between the driver MCU and the charging controller.

So, this is what it ended up as. All surface mounts removed, piggybacked FET+1 driver. There's plenty of clearance for the mounted board. I used a good quality 2 part epoxy to mount, keep it insulated from the lower driver board. Notice the new pads I created on the R and K pads? This is for the RED switch LED and switch to wire from the new driver to the old driver. There's a blue 28 AWG to connect batt+ to the new driver - doesn't need much in power, the batt+ wire to the LED's will be 18 AWG

Here's the switch PCB. Small resistors for RED and GREEN LED's (100/500 ohm), but I'll only use the RED's. Somewhat odd they chose to use 2 RED LED's and only 1 GREN LED. The SMD LED's are dual color.

This is somewhat disappointing. The grease is as thick as silly putty and doesn't spread, even when secured down by screws. I hope the surfaces are flat, and the MCPCB has some contaminants on it. This will get a sanding treatment and MX-4:

That's it for now..

2021-07-27 - continue on, and completed the full mod.

Cleaned up MCPCB:

Nice size:

Excellent thickness:

Shelf cleaned up before sanding:

After sanding:

I enlarged the wire hole, using a metal grinding tip on my rotary tool, here shown from below. It made a big difference. I can now fit either 16 AWG or 2 pairs of 18 AWG without a sharp bend, like it had stock:

Now from above:

Also I enlarged the pads on the PCMCB. Looks like the reflector had clearance for it:

Here's the driver with all wires except the main LED pairs. I tested it out in this form by adding temp LED wires. Notice I tinned the pads and added a 2nd pad for the LED+. Blue wires are 28 AWG, black batt- wires are 20 AWG:

Decided to go with 2 pairs of 18 AWG. The 16 AWG is a lot stiffer and was concerned about the thin small pad for the LED- wire on the small driver. The 2 18 AWG wires should be more flexible, less stress. Had to dremel the wire opening a little on the MCPCB:

Time for the final assembly. Using MX-4, I wanted to concentrate it in the middle and verify it spreads out when assembled:

Wires inserted, carefully pushing down the MCPCB into place:

Last view of the driver with all the wires. Made the pair of 18 AWG little longer than stock so I had room to work with. The 2 LED- wires were a tight squeeze:

View from above, screws tightened down. I can see some of the MX-4 oozing out - good sign:

Assembled view from the backside:

USB-C connector is now gone, giving you a view of the piggybacked driver edge:

Kapton tape applied just-in-case, and stock centering pieces. Was thinking of sanding them down but didn't yet. It can help or make it worse:

The reflector is notched out to allow space for the wires:

Wall shots of the "new" 3X21A. As you can see, the beam color is all over the place. My camera only does auto white balance, high output:

Low output:

So pick your color - white, blue, green!

Fiddling with some camera settings:

It's a nice looking flashlight, even better look'n now with the switch LED controlled by Anduril2

New Measurements

I wasn't 100% careful in taking these #'s, didn't have the light meter at the right scale initially, and when I changed it, I recorded that # as the start number. Also my timing might have been off by a couple seconds.

  • lumens: on charged 40T solder tops: 7330 at start, 6180 at 10 secs, 6000 at 30 secs (mauuka calibrated #'s)
  • throw: taken at 5 m indoors: 335 kcd (1158 meters)

It's certainly a nice bump. Looks like a fast drop over the first 5 secs or so, but very stable slow drop from 10 secs to 30 secs. It's a well designed host, plenty of size for these hot new LED's.

2021-07-28 - another set of measurements, more complete, thorough

  • amps measured on a single 30T at 4.20V: 24 amps
  • lumens: on charged 30T flat tops w/adapter: 7151 at start, 6696 at 10 secs, 6636 at 15 secs, 6424 at 30 secs (mauuka calibrated #'s)
  • throw: taken at 5 m indoors: 360 kcd (1200 meters)
  • parasitic drain w/switch LED OFF/LOW/HI on a single 30T at 4.20V: 35-90-361 uA

These are significant numbers. With my prior used calibration factor based on manufacturer's ratings, the lumens would be:

  • 8024 at start, 7208 at 30 secs

With the mods, the SFT-40 matches or out throws, and exceeds lumens over the 4X18A SBT90.2, based on reviewer's measurements.

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Congrats on your new toy. It looks like you went specific for throw with SFT-40 6500K. Any specific mods that you’re looking at? I’m a flood type with some throw. It’s Cree XHP50.3 for me, though Simon mentioned that a triple XHP70.2 was in the works.

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Yea, for throw, but also lumens. I'm thinking triple SFT-40's can out throw and out lumen a single SBT90.2 for at least $20 cheaper. Maybe the throw is close, or less, not sure. The $20 becomes $40 when they are in a light it seems.

Does the XHP50.3 solve the ugly tint shifting of typical CREE .2's?

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Great review, Tom. :THUMBS-UP:

I must admit, I did not do any side by side comparison with other lights when I posted about my 3X21A sample. If I compare it with some XP-L HI V3 1A 6500K lights, the SFT-40’s white still looks pretty nice. :))

By the way, I have no idea how much beaten up my adapter looks now that I have screwed it on with the batteries installed in the tube, lol. It was totally warped already when I put it on top of the batteries. I didn’t dare to take a peek yet. :D

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I expect the 50.2 HIs will, but unfortunately they’ll likely only come in very high colour temperatures.

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I have 3x21A Sft40 and 4x18A Sbt90. I bypassed springs and sanded down the middles from flattop adapter. Negative end pcb contacts to the flashlight body only with small steel screws. Three in 3x21a, four in in 4x18a.I added three more bigger screws to 3x21a to accomondate that. Still the 4x18a outperforms 3x21a clearly and tint is nicer. I use bundled Liitokala batteries on both.

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For those who might be interested I have few comparisons. Be warned, I’m not a photographer.
Left side 4x18A, right side 3x21A

Bottom of the ramp


Top of the ramp

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You are right - the 5700K SBT90.2 has a more pleasing beam tint, plus comparing a single SBT90.2 to a triple SFT-40, you don't have all the artifacts associated with 3 reflectors. Those deep reflectors show their effect in that last wall shot.

Did you notice or measure a bump with the spring bypasses?

Jumpering out the resistors should be a bigger bump, but does have risks. I'll probably try it first before piggybacking in a driver replacement. I don't have to worry about blowing out the driver circuit. I don't care for the UI in this light at all. The press&hold from OFF should still allow you to ramp. If last used is max/turbo, you'll get blasted with it if you need anything but the lowest setting. In Narsil and Anduril, we accommodate that by adding a delay at the lowest setting, then ramping up is engaged. The linear ramping drives me nuts -- I thought Simon was asked to fix this over and over, I don't get it.

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Truthfully I didn’t notice anything happening after spring bypass. Might be very small increase if anything at all.

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The disk quality is disappointing. I have the 4x18 and the disk is super strong.

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That’s one area I wish Simon would innovate: UI. I can live with quality eccentricity, but UI’s are easy to deal with, especially since pretty much every manufacturer is using Anduril these days. Great lights let down by wonky UI’s. To be fair though, Convoy has gotten better with USB C charging and great single cell lights with e switches.

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The greens in the pics really surprised me. It doesn't look that bad in real life, even on a white wall. If I put it side by side with an old SST-40 6500K, the SST-40 looks blue and this SFT-40 is more on the green side, but not the strong greens in the pics.

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Looks like this light is still one i want to (try) to get, with SFT40. I agree my pictures give it an unfair green look as well, which doesnt show as bad in real life. Sad to hear about the UI, i have been reading about it on the Convoy thread too.. I don't know how i would fix something like that, so' i honestly might hold off on this light until Simon can straighten it out or until i have the pleasure of watching your piggyback mod and determining if it's something i can do. I mean sounds wroth it to buy a $23 astrolux ec01 (Anduril) and rob the driver for a piggyback? is that how it works? lol. i obviously have no idea. Thanks for the insight Tom

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It's common to see our smooth ramping poorly implemented. Back in 2016/2017 during the Q8 development, the Thorfire engineers went off on their own and decided to clone our UI on a different MCU, rather than use the ATtiny85 and our firmware. The ramping in that prototype was linear as well. Thorfire ended up firing the engineers from what they told us. There's been several other smooth ramping lights with the same problems, and typically they make the ramp speed too long, longer than our 2.4 secs (16 msecs x 150). Our ramping tables are 150 entries and ramping increments/decrements every 16 msecs.

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Love those ThorFire’s

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Updates in the OP and post #2 for mods.

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I was wrong I didn’t mean XHP50.3 but XHP50.2 3 volt. The 6500K have the worst green/yellow. 5700K a bit less green same amount of yellow. When outside not much of a factor compared to white wall shots. It’s a pretty drive such a shame a little resistor mod could do it. SFT-40 at 5.66 amps each is factory nice but not around here. 8-9 seems very possible. It does look identical to the 4x18A driver running the SBT 90.2 including the two big resistors rating. Looks like a one size runs everything.

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I guess he amp limited the 90.2 version as well? I think there's something in the circuit to limit amps, not just those big resistors. Not sure what type of current sensing but all those components to the right of the big resistors look like they are doing that, but not sure.

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I hope someone gets to compare sst-40 to sft, in this same light, with such good photos as OP. I have the sst40 5k on the way, but i am wondering more about beam shape than tint, just so I can understand when I should or should not choose sft.

Thanks Tom, great pics and details. I figured I could just use a convoy, but I will look it over for any issues when it arrives, thanks to your tips.

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I should have taken a couple pics of the full beam pattern - there are a few artifacts. I got multi-LED SMO reflector SST-40's that look better, but the power/throw of this flat LED is probably more susceptible to the artifacts, yes - hard to tell unless you can compare them side by side. But also, dunno if they are really noticeable outdoors.