FW3A Troubleshooting / FAQ

Alright, so what do I have to do to run three red XP-E2’s (max 2.5-3.0A/led) safely in the FWA3?

I was hoping somebody would run 3xXHP50.2 3V in there :smiley: But I haven’t seen any triple MCPCBs that would fit.
The end result would probably be a hot light after 2 seconds.

Disable or take the FET off…run off the 7135’s……

1 Thank

Will the UI work with a removed fet?

I don’t know on this FW3A, but I have blown FET’s on FET+1 7135 drivers and the lower modes still worked………

Take one for science… :smiley:

That would work, but keep in mind that without the FET the driver will only supply 2.8 amps. That’s less than 1 amp per LED which is well below the rated max that you described of 2.5-3.0 amp.

If you want something closer to the max possible output of a red XPE your best bet is to modify the firmware or download firmware someone has modified. Wasn’t TK working on a lower amp firmware for LEDs like this and Oslon white flat?

There is a firmware sub-version in her repository for anyone who wants to be conservative with the 219B. It limits the FET channel to 50%. It is also possible to create your own firmware version with different ramp levels.

Because the red XP-E2 has a low forward voltage (and the photo red and far red even lower still), it is probably advisable to avoid FET use entirely unless you’re willing to risk killing a set.

On the other hand, the red and green XP-E2’s seem to have fairly high foward voltages and might work ok with FETs.

Source - XP-E2 datasheet, plus DJozz tests:

Thank you for providing this information. Hopefully it’s an uncommon situation, as it’ll be frustrating to have to purchase a pair of split ring pliers sufficient for the job.

If the ring is loose, tightening it is pretty easy. A toothpick or a nail can generally do the job. But if the ring is tight, loosening it may require better equipment.

Remove the FET then add more 7135’s for your desired current.

Is there room to add more 7135s? I’m not sure there’s enough room to stack them.

There is room to stack them, might have to add a taller spring….maybe, or use a button top?

. I just sat a 7135 on top at 3 O’clock


. Where there is a will there is a way….

I wasn’t so concerned about the spring. I was thinking that with another row of 7135s would there be enough room with an 18650 installed for the battery tube to still close fully. This is one light that has to be screwed tightly together or the switch tube won’t make contact at both ends.

Well I’m not concerned in the least…. just throwing suggestions out there, you don’t know unless you try, thats what modding is all about, if it don’t work, fall back, regroup and attack, repeat…
Personally I like the light just as it is, well these 2x3D FW3A’s I got, no modding needed, but the next 2 warm yuck yellow FW3A’s will be subjected to all kinds of ……fun!

. If you run out of room, maybe a contact on the cap end?

If the ring is loose, tightening it is pretty easy. A toothpick or a nail can generally do the job. But if the ring is tight, loosening it may require better equipment.

can we assume that tightening would be ‘clockwise’? Thanks.


The retaining ring uses the same threads that the battery tube uses to screw into the head. So yes… turn clockwise to tighten.

Thanks, TK. I was just concerned about tightening enough so that it doesn’t loosen later on. I have a cheap pair of split ring pliers that is a little soft—the tips can bend—and I’m just waiting to spot a good deal on a new pair.

What’s a nubbin? It’s not much.
It’s a little cylinder of plastic, shown on the left here:

Picture credit to JasonWW

The nubbin fits into the center ring of the larger piece of rubber, and they both go into the FW3A’s switch mechanism.
The Switch of an FW3A will not work without the nubbin.

When you twist off the tailcap of an FW3A, the switch mechanism falls apart.
They were saying something about glueing the switch, but it didn’t happen, might happen in the future, who knows?
In the meantime, the nubbin is very easy to lose. I opened my tailcap once with no problem, but on the second time I lost my nubbin.
I didn’t even know there was “nubbin to lose.” So I wasn’t really watching for it. Now I need a new nubbin.


It took me about three minutes to make a new nubbin.
I took out one security bit, marked CR-V4, from a set.
You can see it’s got an outer rim and a cup in the middle. This is designed for “security” screws.



Next I hammered the bit through a plastic drink bottle cap. See the left hole? This did not work because my nubbin got stuck inside the cup of the bit. I damaged the nubbin prying it out.
On the second attempt I stopped a little short, leaving a bit of plastic remaining around the outer ring, and the nubbin was still attached to the cap. I cut the nubbin from the cap with a knife.
See the nubbin on the right, still attached?



And finally, you can see my new nubbin, in it’s new home, ready to reinstall in my FW3A.
It seems to work really well. …. at least it’s been holding up very well for a few hours.
You also see the drill bit on top, and on the left, the nubbin that got damaged.


I had a half dozen more bad puns ready to go, but decided it’s better if I don’t.
If others would like to join in, there’s nubbin stopping you.

I wonder if a large-ish drop of super glue (or similar) on the rubber insulator/seal would work to replace a fugitive nubbin?

Super glue usually does not stick well to rubber. Goop works well with both plastic and rubber.