H17Fx Driver help, FET not working

Hey all!

I have been loving my H17Fx driver in my E3. But I have felt it should get brighter on the highest modes than it was getting.

I just got a UT210E and measure the tailcap amps around 3A with fully charged vapcell H10 and 7A discharge 14500s. I now assume the FET driver is just not working as those max amps suggest nothing beyond the 8*7135 being engaged.

This is what the driver looks like when I took it out to photograph it.

Of course I did not photograph it before installing… :person_facepalming:

Does that “bump” on what I assume is the FET explain what I’m seeing? I’m not sure how I would have damaged it. Is it possible excess heat from that cathode wire made the damage? Seems strange to me considering the FET driver itself would have created a lot of heat in use.

Also, even with my crappy DMM I never measure more than 3A at the tailcap on turbo. So I’m wondering whether it came damaged…

What do you think?

Someone more knowledgeable will hopefully come along and help. I’ll do my best until then though. Is this in a Jaxman E3? If it is in a single LED host depending on emitter, springs, bypasses, etc. it might be that 3A is all the cell is going to be able to push. Just because a cell is rated for 7A does not mean your light will draw that much current. You could enter into programming with the clamp meter set up, go into the brightness adjust setting and then watch what the current does and see how many modes you are getting. It should be 24 modes. If it just stops ramping up in current towards the last few modes it probably means that 3A is just all you are going to get in the light with the present setup. If it has a single xpg2 in it, I think that may be the case.

I hope that helps. Best of luck to you. I love those drivers too.

Hey thanks for the reply!

So yes, it is an E3 with a LH351D 4000k emitter.

I have it hooked up to the clamp meter running through the ramping mode choices and it doesn’t go above 3A in the top two modes, and doesn’t get any brighter. That’s what makes me think it is a damaged FET.

On my modded Tool AA 2.0 with a MTN-15DDM FET+1 driver, LH351D, and H10 cell I am pulling 5.5A at the tailcap on turbo.

I’m wondering what else could be different about this setup other than the driver functioning, generally, or a damaged FET on the H17Fx. Is the H17Fx not going to have a similarly functioning FET?

My H17Fx has a brass button, as well. No spring.

Unless something is adding a bunch of resistance for some reason, it seems like you should get more out of that set up. I was under the impression that if the FET was bad the top modes would not stay at 3A but the light would turn off. When power is diverted to the FET channel if the FET is not working or removed, no power goes to the LED. I suppose it is possible that something is wrong with the FET which is making it limit current. I don’t know enough to help you there. As a sort of electronic switch though I would think that it would either just work fine or not work at all, at least the vast majority of time. Sorry I can’t help more.

That’s interesting. It would make sense if it weren’t working at all it would just turn off as opposed to remain at 3A.

I wonder what’s going on there. Could be a firmware problem, I suppose. In which case I’d be at even more of a loss!

Have you used the H17Fx before and measure the tailcap amps on turbo?

Anyway, thank you for adding you two cents in here. I appreciate the help.

I tossed a 219B sw35 in there in place of the LH351D, because it won’t be pulling more than 3A anyway. And I love it this way too! It gets super low and plenty bright for an EDC. Still happy!

Does it still pull 3A with the Nichia? If it does I would imagine it’s the FET. The 219b’s have a much lower forward voltage. I have never measured current because I have a garbage multimeter. I have used those drivers in 6x Luxeon V2 light though. That definitely does more than 3A! I’m asking for a clamp meter for Christmas. Hopefully I have been a good boy :slight_smile:

Sorry I can’t help more. I avoided talking about the spot on the FET because I’m not up on the details of components. I just don’t know enough to be confident about anything. I’d think that spot plus being stuck at 3A with a different LED would be a pretty good indication that that is the problem.

I will try later tonight with the clamp meter to see if the 219b pulls more than 3A with the Vapcell 7A.

The 219b is on a DTP MCPCB, but I’m still kind of worried I’ll fry it by putting more than 4A through it even for a second.

Is that a reasonable fear?

That’s a reasonable fear. I’d be concerned about using a FET driver and that LED. I think those have taken 5A ok for a short period but it might pull more than that. I’m not real up on the Nichia’s though. I thought you had already done this and it was ticking along just fine. But I guess you swapped LED and Driver?

I haven’t changed the driver, but I have run it through its full range of modes with the 219b, albeit without a clamp meter. So know it probably won’t go poof, I guess!

I just used the clamp meter and ran all the modes with a fresh Vapcell 7A. It goes up and up and hits 3.04A and doesn’t go up, stays there, then goes down again.

So I guess that means the FET isn’t engaging, huh?

It is just fine for this setup with a 219b, though. I am just hesitant to buy more H17Fx. I really like the driver, but for other builds a working FET channel is a must.

If you are using a battery with high enough internal resistance the led should be fine. It’s the high drain cells you need to worry about.

Each 7135 puts out about 0.35 amps, I only see two on top so there would have to be about seven more on the bottom to get three amps to the led without the fet.

The bump on the fet does not look normal. One way to test it is to use the diode test function to drive the gate full on. It’s best to do this at the attiny as you are less likely to short something out if the probes slip. You should be able to see which attiny pin drives the fet gate by following the trace back from the scr, or use an ohm meter. You will probably come across a resistor along the way, test the resistor to see if it matches the value printed on it.

Power the driver up with an led connected and put the driver on the highest mode. Place the meter in diode test and put the negative meter probe on the ground ring. Briefly touch the positive probe to the fet pin and see if the led gets brighter. If it does get brighter there’s something going on with the attiny or you are not in turbo mode for some reason. If it doesn’t it means the attiny is properly driving the fet and the problem is a high resistance in the circuit somewhere. Probably a bad fet or a crappy spring.

Hey WTF, thanks for the response and info!

The H17Fx has 8*7135 chips and a FET. There are two on top and six on the battery side. Check out the specs here. It also has a brass button instead of spring.

I was also using a high drain 7A Vapcell Blue and a high drain 10A Vapcell H10. Both were freshly charged and I tried multiple batteries. That means it’s probably not the battery, right?

Thank you for the details instructions on how to test for a properly functioning FET with a diode meter. I will take it apart at some point and check it out and see what happens.

I don’t have a great setup to test the driver outside of the flashlight, but hopefully I can build one soon.

Thank you!

Regardless of what is up with this one I wouldn’t worry about buying more. I’ve bought probably close to 20 of these drivers and never had issues with the FET channel. They are a little pricy but the firmware is absolutely perfect for a large number of setups, like high powered edcs. Best of luck trying to figure things out.

Cool. I love this driver, so that’s good news!

Definitely the best UI I’ve used so far.