Puzzled by VariCool behavior

[Rickajho]

I bought a VariCool VV box from smoktek last year and it's worked ok.

Last month I decided to get another one now that a different box color was an option.

The first new one worked for about 6 days and then "shut down." Of course I just thought the batteries were depleted. Put freshly charged batteries in it and... not firing. The LED comes on but it wasn't firing. Ok, try the atty on a different PV and the atty is working ok so that wasn't the problem. Atty back on the VariCool - not firing.

At this point I get out the meter. The LED lights but the VariCool is showing zero volts at the 510 connector.

I got an RMA to return it but the box sat for about a week before I could get to mailing it out. Sat there with nothing on the 510 connector, with the same batteries it would not fire with, power switch off. Decided to give it a "what the heck" and put the very same atty back on it and... now it's working again.

For five days... and then it shuts down again.

Got the replacement box and guess what? Worked for 5 to 6 days and the same thing happened. Shut down - LED lights but reads zero volts at the 510 connector. I will be checking it daily to see when it decides to work again.

It's not like I'm beating on these things either. The only thing I've used on them are SR JoyeTech eGo MEGA cylinder attys. (Liberty Flights calls these eGo XL type B attys.) The two attys used on the boxes only meter at 2.6 and 2.8 ohms respectively so I can't see that as the source of an issue. This highest voltage I've pushed on the boxes has been around 4.2 volts

For such a relatively simple VV design, can anyone hazard a guess as to what's going on here. I could understand component failure leaving a box dead and gone. But why this "works 5-6 days, shuts down 5-6 days, works again 5-6 days..." cycle.

I could understand a regulator shutting down due to some kind of internal protection. But shutting down for nearly a week at a time?

I really want this thing to work. But this is just baffling.

 

[Gldnmom]

I had the same experience! A few months ago I sent one back (which they told me was working fine when they got it)! The replacement worked for only a couple of days before it stopped. I gave up!

 

[Rickajho]

I certainly can't fault SmokTek when it comes to customer service. And they did replace the box no questions asked. But I did caution them to check out this problematic box for an extended period of use since mine was exhibiting a "5 day on, 5 day off" kind of cycle.

But now to have it happen to two boxes in a row? And both do the same thing in under a week of use?

What could possibly be going on here?

The only thing obvious between my original box and the newer, problematic ones I got is on the latest boxes the regulator PCB is now buried under a coat of hot glue. On my original box there was no glue at all on top of the regulator board. Could that make a difference?

Any technical people peeking at this thread?

 

[Rader2146]

That is quite puzzling. Without taking readings with a multimeter it is nearly impossible to diagnose. Since its covered in hot melt, it's even worse without voiding any warranty.

The regulator used in the VariCool has 2 shutdown modes, undervoltage and thermal, and a current limited short circuit mode. Obviously fresh batteries will remedy the undervoltage, and if it were a the thermal issue you should be able to feel at least a little heat from the regulator. Thermal is very unlikely seeing as we don't run continuous output and it certainly wouldn't take days to cool down and be operable again.

Short circuit could be a possibility. Maybe a new batch of connectors that didn't match well with your atty. Did you try different atty's? Do you screw the atty all the way down tight? In short circuit mode the regulator limits output and continuously checks to see if the over current condition is still there. Once the condition is gone it will automatically resume normal operation. Maybe try holding the fire button and Slowly unscrewing the to see if there is a point at which it will fire; I believe the technical term is "fiddle with it" while holding the button.

 

[Rickajho]

Yes, I have done the fiddle thing but will fiddle more. (What else can I do with it?) Tried hitting the button repeatedly with power off, button repeatedly with power on, brand new batteries, new atty... zippo.

Regarding the connector, ST is using a different one. My original box had an unsealed connector. The new boxes both had sealed connectors. I'll take a good hard look at the center post later to see if anything obvious is showing. But this last time it went from working to not working with nothing having been fiddled with on the connector. One hit it worked, the next hit - not working.

Odd point: The last time I checked the voltage at the 510 connector I got a very short jump to 0.24 volts - for a split second - and then it rapidly dropped to zero volts and stayed at zero volts. Does that mean anything?

 

[Rickajho]

Fiddle, fiddle, fiddle. Ta Da! Ok, it's something to do with the 510 connector. (Gldnmom take note...) But what's it all mean?

Looking down into the 510, the center post appeared all perfectly centered and nice and shiny and clean. In another "what the heck" moment I decided to pull the center post. I barely manipulated the center post - just the tiniest bit - slapped my atty back on it and it's working again. Ok, that's good.

BUT...

I'm puzzled about this. It seems to make sense that something about the 510 connector was shorting out. But where? A hair's push in and it's shorting something at the back of the 510 connector? Shining a really strong light through the glue surrounding the 510 and switch wiring I suspect it's the center post wiring tab. It looks like it's riding awfully close to the outer part of the 510 connector. (With some admitted optical interference going on from the glue.)

So I fixed it - for now. Question is: Is it safe to use until it shorts out again?

The idea that this happened at all - with two boxes no less - really surprises me. I'm one of these people on ECF always lecturing noobs about the perils of overzealous screwing - the problems associated with screwing cartos etc. on too tight. And how to fix things if they have pushed a post into a battery, a center connector into a charger etc. I'm not the type of vaper putting stuff on that practically needs vice grips to remove it. Far from it. Barely finger tight and no more. So the idea that a center post got pushed in on either of these boxes within a week wasn't on my radar. And I didn't think, based on their construction, that you could short the 510 connector on a VariCool.

This also explains the works... doesn't work... works... doesn't work... cycling. Tiny push in - it was shorting. Let it sit and tension on/from the center post o-ring pulls the post back up. Use it some more and the post moved again and shorted. And repeat. We're probably talking the tiniest fraction of a millimeter in movement making and breaking the short I saw.

Anyway, it's back to working for now. This is gonna have to be one of those "time will tell" scenarios.

For anyone who experiences similar weirdness with a VariCool pulling the center post - even just a hair - is definitely worth trying. I hope Gldnmom still has the box so they can see if this fix works on theirs.

Noodles to say I will be in touch with SmokTek.