So far we tested the faulty station and guess what: It is working perfectly well, each and evry time!
Do you believe this?
Needles to mention that we don`t know anything about what caused the problem and which component failed. Was it a good idea to call all the units back? I am not sure about this anymore but what else should a company do in such a situation?
Of course I can believe it, in fact it's what I would have expected. An intermittent as opposed to a hard failure. In all likelihood no component has failed in the conventional sense. A design/programing error perhaps, or assembly workmanship error, but not a defective part. They tend to fail hard, or at least repeat reliably.
No common part defect I know can explain the symptoms.
Was it right to 'call them back'? Absolutely. Advise folks of the risk. IMO no choice until 'we' know more, right now the product doesn't meet spec under as yet not understood conditions that can cause safety issues.
Exactly the sort of hand Murphy (of 'Murphy's Law' fame) would deal given the chance.
My feelings are telling me, that the problem must be somewhere around the heating cartridge with the thermocouple, I don`t think that the electronics failed. These days, electronics are very reliable, thinking about all the electronics we are using at all times, like now when I am typing these words into the computer.
Anything is possible, but I doubt it highly. Failures in such devices are generally hard, they don't suddenly 'get better'. An open or shorted heater or T/C is generally very easy to spot. And the design of the unit should be such that it "
fails safe" in such cases. I assume it is. That is a defective heater should (more commonly) go open and stop heating. If it suddenly goes 'too hot' (like shorted turns in the heater) that should be sensed by the still working T/C and compensated by the controller in due course (the owner might not even know it's happened as a duty cycle shift is all that happens 'on the outside'.
Likewise a
T/C failure should be safe by design. In the event of an open the logic should recognize out of range readings and shut down. T/Cs should accurately return readings (one of the reasons they're so popular) or be easily detected for shorts and opens by design.
Other failure modes, like say leakage current rise in the pass element (electronic switch that turns the heater on and off) can be a hardware issue (perhaps related to heat) are more likely IMO. Software can of course cause this as well by 'forgetting' to turn the heater back off by being distracted or stalled. A common 'belt and suspenders' approach here is to have the processor key 'a hardware one shot'. That is a timer that independently turns the heater off again some short time later. As long as the processor keeps cycling it (resetting the timer), fine, but if that cycling stops after a 'timeout' of say half a second hardware shuts it down anyway.
While modern electronics is indeed very reliable in an appropriate design, that last part is not yet a given. Dell and Apple have made huge numbers of products, many 'first attempts' have these sorts of issues crop up. This is, of course, exactly why you do pilot runs and Beta testing? To prove the design solid in the real world.
By all means break it into pieces and examine each, "divide and conquer", a powerful troubleshooting approach. The answer is out there somewhere. If it's a rogue component that will be a job to catch. You'll need to identify and isolate it, then get that part to repeat the failure when transplanted into a different (problem free) unit. "Root Cause Analysis" can make you old before your time for sure, but confidence can only happen after that. IMO a 'top down' design review might be key. Examine carefully how the software handles things. How it controls duty cycle, does 'reality checks' and so on.
Until then, as the saying goes, "problems that go away by themselves come back by themselves". Not a good thing to leave running unattended.......
Regards and best wishes. IMO the HS is just too cool, the vape world really needs this one......or at least wants it mighty bad......or should if they know what's good for 'em.
OF