Solved! Thanks everyone! Strange flashlight troubleshooting problem? What is wrong?

Hi everyone.

Bit stumped.

Light is AAAx1 Nighthawk Bantam twisty 2-mode. Last night, I pulled it out and it was dead. Put a different battery in there, still dead. Put the battery in another light, it worked.

Cleaned the contacts, the threads. Rubbed the battery positive connection on the driver. Still dead. Put a pencil eraser down the body and twisted it against the triple tail contacts. Still dead.

Bypassing the body, holding the battery to the driver and making contact from neg to the head threads, it lit. Okay, "twisty switch bypass" works. It comes on low, so worst case I hack it to a D battery and call it a day.

Here's where it gets weird. With the battery in the body, placing multimeter across positive and the threads reads continuity and voltage! HUH?

Am I losing it? Do I need to hand in my flashaholic card?

As a last resort, I was considering adding solder to the positive contact pad on the driver. Don't want to fry it. It actually works when you bypass the twisty/the body. Using longer length battery really jams it up against those contacts, much harder than an Eneloop. It's GOT to be making contact.

Any ideas? Driver is QTC (I think, head tight and head not-so-tight are the modes) and adding the solder will probably mess that up if my thinking is correct.

Nighthawk had a 10 year warranty, but they are out of business. (I just found out this morning.)

I was thinking jump soldering the outer contact ring of the driver with the pill, maybe there's increased resistance and I don't think the driver is soldered to the pill. Just a press fit (that doesn't look that tight.)

Re: Strange flashlight troubleshooting problem? What is wrong?

more_vampires said:

Here's where it gets weird. With the battery in the body, placing multimeter across positive and the threads reads continuity and voltage! HUH?

Click to expand...

All volts across an open. That is, the meter is completing the circuit and reading voltage.

However for you to be able to verify continuity, that suggests a weak link which cannot pass the current. In my experience, this is usually a bad solder joint.

Re: Strange flashlight troubleshooting problem? What is wrong?

Thanks for the thoughts. The circuit must be open somewhere, somehow. But where?

This light has always been finicky wrt dirty threads. It's got to be some kind of contact problem. Multimeter eliminated the triple tail contacts, the pill is definitely squashing down the battery, I hear no battery rattle at full tightness.

Going to try jump soldering the driver to the pill (after a good long pause for healthy reflection.)

Don't want to junk the light, but at least I can hack the head if the mysterious problem can't be located and fixed. I will not throw it away, it's been a great EDC for some time now. (3 yrs?)

It wouldn't be so aggravating if bypassing the body didn't light the light. I'd say "oh, junk driver or open emitter. New driver and reflow." 10mm driver, btw. Not very common...

Re: Strange flashlight troubleshooting problem? What is wrong?

I am gonna throw a thought.
Is the Oring moving or getting pinched in there? I had a similar problem as you described only to find the Oring was torn and would keep the tail cap from making full contact. The only other thing I can think of would be a dented battery??

Re: Strange flashlight troubleshooting problem? What is wrong?

Thanks for the sounding board to bounce thoughts against. I appreciate it.

NH Bantam is solid tail, no removable tailcap. Head double O-rings are in good shape, considering what they've been through. That could have been it, certainly.

Unfortunately, that's not it. I'm still thinking before I pick up the soldering iron. I've wrecked too much stuff by going off half-cocked.

I'd be glad if it were something that simple. A little embarassed, but I'd be happy to have my light back.

Re: Strange flashlight troubleshooting problem? What is wrong?

Solved! Okay, I feel a little dumb.

Apparently, the NH Bantam has a somewhat high cutoff voltage. I'd never noticed it before. As it just so happened, the two other batteries I tried from functioning lights were below its cutoff voltage. The primary AAA I grabbed from my vampire stack was below its cutoff voltage! It was one of my fresher ones. I never suspected the cutoff is so high.

Solution: Charge the d*mn Eneloop. Sigh. I'm certainly glad I backed off and thought about it before possibly ruining something. I was about to fix something not broken.

So the NH Bantam has a higher cutoff voltage than some lights. It's still super-light and versatile.

Thanks again everyone. I was right, contact was being made, but this raises further questions:

Bypassing the body, holding the battery to the driver and making contact from neg to the head threads, it lit. Okay, "twisty switch bypass" works.

Click to expand...

It seems non-intuitive that the head magically has a lower cutoff voltage when removed from the body. The "dead" battery lit it up when not screwed onto the body!

That's just bizarre! I confused myself with troubleshooting! Oh well, goes to show that we all have our off days. At least this thread didn't drag on forever.

Thanks again everyone.

This thread: 12:54 pm to 2:25 pm. Not my best troubleshooting times, I must admit.

Edit: Icing on the cake, my Eneloops I've been EDCing for 3+ years are dying.

Re: Strange flashlight troubleshooting problem? What is wrong?

Ha! awesome. Glad you figured it out. "No removable Tail Cap" Cool. I just googled that light. Not familiar with it. Looks pretty neat thought.

Re: Strange flashlight troubleshooting problem? What is wrong?

Oh yeah, they're great. Bad news is afaik, Nighthawk shut down. What's up with all these small-house flashlight businesses going out? I was going to buy another one and worry about "fixing" my non-broken light later. Couldn't even do that.

They're unobtanium now. It's my shortest and lightest OAL AAAx1 light. They were pretty good. Spot thrower optics, rare in an AAAx1 light. Oh well, we'll see who fills the void.

Edit: No, wait! They're available! $35! Just found an online shop with 1 left, possibly the last one left in a store.