Mysterious black stuff on + contact of Infinity??

I retrieved an old white Infinity Tasklight from my sea kayaking vest tonight, switched it on, it seemed to work, and then I noticed the clip had rusted some. Took the clip off, rinsed the remaining rusty deposits off the barrel of the light (don't think I got any water inside), turned the light back on after drying it carefully, and only got a couple flickers then the light wouldn't light. Removed head, put in fresh (tested) battery, got a couple more flickers, then nothing. Unscrewed head, saw some black deposit on the + contact, took knife and scraped it down to bare gold contact. Light worked.

What do you suppose was the black stuff I removed from the + contact? Do I recall reading in the deep dark CPF past that it's actually supposed to be there??? Help please?

Thanks. /ubbthreads/images/graemlins/smile.gif

Re: Mysterious black stuff on + contact of Infinit

Silicone grease mixed with Al oxide from the threads? Some kind of corrosion?

Re: Mysterious black stuff on + contact of Infinit

Yes, the black coating is supposed to be there. I believe it has some resistive properties? Back before the advent of the Infinity Ultra, people would scrape off the black coating and get higher light output- similiar to the Ultra.

I just checked one of my older Infinities and, yes, the black coating is there. The light has always worked perfectly after several years of regular usage.

Re: Mysterious black stuff on + contact of Infinit

My understanding of this is only second hand and as such could be WAY off base. I seem to recall reading somewhere (perhaps Mr Museum?) that at one time CMG put a gob of this black goop on the contact to act as a crude dimmer. I dunno. I also am not at all sure where I read that.

A few weeks ago I took delivery of two old Infinities in 'gift tins' that were found when they cleaned out the Chicago CMG office. These are the ones with green LEDs that I got from the Battery Station CPF Special page. They do in fact have black goop on the contact right out of the box. I also have a flawless amber infinity that I bought at The Led Light Bargain Basement which has the goop, although it did not come in a tin.

The goop actually does work to dim the light...more or less. The way it sorta works is nothing to write home about. I've played around with it on all three lights and it is kind of cool in a very marginal way. It's hard to get the level you want, but I can see how if you perhaps had a task where you need less light and you were going to leave it on for a while without messing with it, you may be able to make the battery run a bit longer. I think that what I read before about it was that many scraped it off. It must not have been much of a hit because none of my newer Infinities have it.

I've left it on the three that have it, knowing that if it starts getting creepy I can always scrape it off.

Re: Mysterious black stuff on + contact of Infinit

Unless I'm mistaken, the black stuff would be a carbon based contact material. One day when you have the chance and a dead calculator or pc keyboard, pull the keyswitches apart and you'll see buttons made of carbon type material acting as the contact points.

The reason they use carbon is that metal to metal contacts grind away at each other (if made of disimilar materials where one is harder than the other) or gall (if made of same materials.) The carbon should be self lubricative and prevent such issues.

Another way to look at this - the nipple of the battery comes into contact at this point. The battery contact is steel - it comes into contact with the bare circuit board which may have a contact surface of copper or gold plated copper. The flashlight is rolled so the battery spins and the nipple rotates against the contact. Any slight surface defect will cause the hard steel to cut into the soft gold and copper and eat away the contact. A surface coat of carbon will resist this by acting as its own lubricant.

You can get stuff like this through CAIG if you need/want to repair it.

Re: Mysterious black stuff on + contact of Infinit

Thanks fellow CPF-ers!

Blackbeagle:

Let's see, I've seen the word CAIG, but if I ever knew what it stood for, I don't anymore. /ubbthreads/images/graemlins/icon3.gif

Re: Mysterious black stuff on + contact of Infinit

CAIG Laboratories. They make contact cleaners and the like. Good stuff.

Re: Mysterious black stuff on + contact of Infinit

I bought one of the green Infinity lights from BatteryStation and had the same problem. I called BatteryStation and the gentleman told me that it is a potting compound used to seal the electronics on the head of the light. Some of them had too much put in when manufactured and it got on the contact for the battery. I took a plastic putty knife and scraped it off then cleaned it with alcohol. It's working fine now.

Re: Mysterious black stuff on + contact of Infinit

Thanks PJ, but I'm almost certain it's not potting compound. It was a coating on the positive battery contact on the printed circuit board in the head of the light. It indeed looked like what others have suggested above, a carbon-based material with slightly lubricious (real word?? /ubbthreads/images/graemlins/icon3.gif) properties that was placed on the contact on purpose. What the problem was that caused my Tasklight to malfunction I'm not sure. All I can say is that after I scraped the material off, the light worked fine. Perhaps long term exposure to moist salty atmospheric conditions (it was my sea kayaking light) in combination with the lithium battery being in there for basically years caused some chemical wierdness that screwed things up electrically. I let the light run for several hours after removing the material, and the light does seem to work fine.

Re: Mysterious black stuff on + contact of Infinit

[ QUOTE ]
PJ said:
I bought one of the green Infinity lights from BatteryStation and had the same problem. I called BatteryStation and the gentleman told me that it is a potting compound used to seal the electronics on the head of the light. Some of them had too much put in when manufactured and it got on the contact for the battery...

[/ QUOTE ]

Emphasis mine.

This does not appear to be the case with my lights. On my lights that have it, it is applied in a perfectly circular manner, only on the + contact. If it were an accident I would expect it to be more randomized in shape and placement. This is not the case.

Here is a link to Quickbeam's review of the Infinity Task Light. While he does not mention the goop, note that his excellent review contains two photos of the circuit board with the goop plainly visible. As on my Infinities, it appears to have been applied very carefully, in a perfect circle, and only on the contact.

Every one that I've seen look as though a great deal of care went into applying it. If it was the result of an accidental application we could reasonably expect to see little 'swirly trails' and blobs in places other than perfectly covering the circular + contact. I would think that an excess of potting material might show itself by squirting out around the edge of the board rather than appearing mysteriously in the center every time without even leaving a trail from its origin. I would also expect an accidental application to not be of uniform thickness on each light. If it were thicker on some lights than others I would expect to see deformation of the goop in one direction or another the first time it is assembled with a battery and turned on. This is not the case in mine or in the photos of Quickbeam's review. If anyone has pics of an old Infinity with any goop that looks in any way randomized, and not just worn, I'd like to see it.

It is certainly possible that the discription of events that the guy at BatteryStation gave you has, in fact, happened at one time or another. I would expect so. I just don't see anything in my lights or in the pics in Quickbeam's review that would indicate that that is what is going on in most of these lights.

Re: Mysterious black stuff on + contact of Infinit

Now that I have taken it apart and looked at it again it does appear that the compound was applied on the contact only. There is some of the compound that appears to have leaked out on the side of the board. It doesn't seem to have any lubricating quality to it, more like a thick tar. If I recall it took a little effort to scrape it from the positive contact. I have a picture of it and I'll try to post it to this thread.

Re: Mysterious black stuff on + contact of Infinit

Wow! You guys don't know what that stuff is, eh? It actually serves as a sort of RESISTOR! Scraping it off (or actually heating it carefully and wiping it off) would allow the battery direct contact with the light's contact and it should be about as bright as an infinity ultra, along with the resulting decrease in battery life. With the black blob, the light is dimmer but has a much longer battery life. Carefully twisting the light on until it just turns on (with the black crud on the contact) and then gently increasing tightness will allow it to come on dim and gradually increase in brightness (that's your dimming capability).

The newer infinities and Gerber branded infinities just use a different boost circuit instead of the goop to get the longer batter life/dimmer light.

Re: Mysterious black stuff on + contact of Infinit

Cool! That means I have three cuasi-Ultras on my way from Kevin... hmmm...

Is this "misterious black stuff" (to use the techincal term) something we could apply to a newer Infinity Ultra to prolong batt life, with reduced output? Why would someone want to do this? Well, just 'cuz it can be done (I think). Seriously, if you really wanted to use the Infinity (or any other light for that matter) as a disaster-only light, you could apply this stuff a priori to maximize batt life. Is this stuff really the same as what comes in the back of the calculator pads?

Re: Mysterious black stuff on + contact of Infinit

I wonder if it's a 'two part mix' or can be used out of a tube?

I'd love to have some to play with if it could be had in consumer quantities.

Re: Mysterious black stuff on + contact of Infinit

Sorry guys, you've reached the limit of my knowledge. No idea what it is or how to get some... /ubbthreads/images/graemlins/frown.gif

Re: Mysterious black stuff on + contact of Infinit

Try Caig.com - Caikote 44.

Re: Mysterious black stuff on + contact of Infinit

Scraped off the "black stuff" from my Infinity a long time ago and applied a drop of solder to the contact. My Infinity is still half the brightness of an Ultra, but reaches a consistent level as soon as it's turned on. While the "black" was there I had to crank it down.

Perhaps someone left over from CMG could shed some "light" on the real reason for the "black"?