AAA UV weird problem

This past week I bought an Arc AAA with a UV LED. It worked well the first night I played around with it looking at $5, $10, $20 bills and checks, etc. But the next day when I went to turn it on, it wouldn't. I unscrewed the head completely and screwed it back on. It worked again. Then I put it down for about a minute and tried it. No go. Unscrew and rescrew head again. No go. Take out battery, put in different one. It works. Put old battery back in. Works. ???

So, I figure it's the "bad ground" problem and begin to investigate with my multimeter. One multimeter probe to the head threads and the other probe to the thin ring trace around the inside of the PCB. Full connection. Ok, maybe it's just intermittent and I happen to test it while it's making contact properly. So I use a small flat-bladed screwdriver to dent the edge of the threads into the ring as Peter describes in his AAA repair thread. I then attempt to solder the ring trace to the head in one tiny spot. Multimeter still reports full connectivity (0 Ohms resistance) between the PCB and the head. I reinstall the head into the body. No go. I wait 20 seconds. It works. I twist it on and off once per second for 5 seconds. It works each time. I turn it off and wait for 10 seconds and then try again. It doesn't work.

So I remove the head from the body and grab a piece of wire with both ends stripped and the AAA battery. I hold the head in between my fingers and press one end of the wire against the threads. I hold the battery with my other hand and press the other end of the wire against the negative battery contact. I begin to test by touching the positive battery contact against the middle contact point on the Arc head. It works. I try it in 1 second intervals for 10 seconds. It works every time. I stop and count to 10 or 20 seconds. I try again. It doesn't work. I keep trying to get it to work every second for 10 seconds. No go. I stop and wait for 20 seconds. I try again. It works. I can repeat this process indefinitely.

Anyone else seen such strange behavior? Peter, I feel like you should take a look at this. What do you think?

- Brian

I've had that problem before with the ARC AAAs. You probably need to do the "Roll Crimp" to fix it.

Surefire M6,

I thought the roll crimp was done to make positive contact between the negative ring trace on the PCB and the threads of the Arc head. I have already ensured that positive contact is being made, including a small solder joint going from the ring trace to the head. I fail to see why the roll crimp will do anything more to help. Please explain.

- Brian

Brian -

You're right on all accounts. You've effectively done the roll-crimp - even more effectively than the roll-crimp itself.

Out of my sampling of 50 or 60 AAA's I've had to send back two or three that simply could not be repaired "in the field." If I can't get it going after the amount of effort you've just described - I send it back.

It does sound weird as you say bmsmith. We have heard of these symptoms but in every case it was solved by fixing the ground. Since you already covered that, you may have something else. There are also rumors that some cells develop an internal intermittant connection. At this point, I really don't have any idea what is causing this particular light to exhibit these symptoms. We are happy to study it for you.

Peter

FYI: Mine does the same thing. If I clean the contacts real good I can do about 2 days without any problems, but then it's back to it's old ways. I wasn't sure how long it would take to fix and I needed it this week so I haven't sent it in yet, as soon as I can part with it for a bit though (I mean I do have another fine Arc product...) it's going in.

Here's another interesting tidbit for you Peter: When I froze my Arc AAA it turned itself off and refused to come back on until I used a second battery--but then putting the first one back in worked.

I had the same thing happen to a standard and an LE. I sent both back. The replacements that Peter sent me have worked perfectly thus far.

I recently bought a UV model that does not come on all of the time. This occurs much less frequent than with my first two AAA's.

It seems to happen when I turn it off then on right away.

could it be due to a weak battery causing the arc's regulation to take some time to kick in? i get this problem once in a while with my arc as well but it usually only happens when the battery is dying.

I think it's the inverter not working when it should. The fact that I can wait for exactly 20 seconds to make it work (if it doesn't work the first time I twist the head "on") leads me to believe a capacitor is discharging and allowing it to work with the second twist. Since the invertor is an oscillating circuit, the first twist probably isn't starting the circuit properly and it "hangs". Waiting 20 seconds allows the capacitor(s) to discharge to a level where the second twist works correctly and the circuit begins oscillating and inverting. Plus the fact that it is perfectly repeatable leads me to conclude it's a circuit/component problem and not a grounding issue.

It has nothing to do with the battery. I've tried several, both new and old with the same results.

Pete, I think I'll send this off to you. I really appreciate the service and the product. My AAA LE works awesome, so I know what Arc is all about and what to expect from an Arc AAA.

- Brian

It's this sort of flaw that reminds us that semiconductors do work, but the explanations of how they work depend on quantum mechanics.

All it takes to make electronic gear unpredictable is some random cosmic ray or electrostatic discharge that alters some threshold level away from the specification. Some part of the material changes the voltage at which it quits insulating and becomes a conductor -- maybe even part of the material making up a component changes, not all of it -- and lo, Schrodinger's Flashlight.