Blue Ring Sporadic multiple lighting...

stocknic

Hello! I've built a few of the bulbdial clocks already but haven't come across this issue before and wondered if you could help me? On setting up the Blue LED ring, there are a couple of LED's that seem to flicker with another..for instance D35 causes D34 to flicker a little..I've checked all the solder joints, checked the microcontroller (by swapping out another chip, problem still persists) and am wondering if there's a micro short somewhere that I can't see...any ideas where I should look?

Many thanks for any assistance you can provide!

Cheers,

Nick

Windell Oskay

I have seen my share of bulbdial oddities-- we've learned to help debug all of the different things that can go wrong --but I can't recall seeing anything that someone might describe as "flickering."  Can you say a bit more about exactly what it is that you're seeing?

D35 and D34 do share a line in common, which is the LED5 signal, originating at the right side of R3. If one or both of those LEDs is electrically bad, it could (I suppose) cause something like this.  

I'd also suggest carefully checking the area at those two LEDs and around them for possible solder debris such as actual little bits of metal or excess solder flux. And, try stressing the LEDs mechanically (just a little push-- not enough to rebend them) to see if that affects it.

stocknic

Thanks for the quick reply Windell! What I mean by flickering is that when the unexpected LED lights up it flickers on and off randomly (like you have a poor connection on something), then the next time around the ring it wont light and then it may again the next time, it's kind of random....odd. I will check the areas you mention and check for stray debris with the magnifier...I'll also give the LED's a gentle 'tweak'.

Cheers,

Nick

Windell Oskay

That's odd; it definitely sounds like a bad connection or bad LED type of problem.  

You might consider putting it into the "manual" LED alignment mode, to see if you can leave just that one LED on for a while and observe its behavior as you tap on stuff.

stocknic

Hi Windell. I've been trying to figure this out and I've come up short. I've replaced a couple of suspect LED's, still the same issue...in fact I've now seen completely unrelated LED's illuminate unexpectedly...it's like there's a ghost in the system! Just to make sure I'm not completely crazy, I just finished the Blue ring on another kit and its working flawlessly (a few of these boards were in a backlog of kits I had...and Xmas is coming up...these things make pretty nice Xmas gifts!). This board appears to be particularly sensitive to touch capacitance from my fingers and will occasionally shut the LED's off or even advance an LED or two at a go....not sure what to do next...any ideas?

Thanks,

Nick

Windell Oskay

If it's sensitive to capacitance, it could be that there's an issue with the capacitors on the board-- in which case a small change in external capacitance could cause a large shift.  Check to make sure that all of the caps are in the right places, with the right orientation (for the big electrolytic), not cracked, and soldered cleanly. And again, see if you can stimulate a failure by tapping or prodding any particular component. Try to use something like a plastic pen to tap them, to minimize the capacitive issues. 

stocknic

Hi Windell, I've replaced C3 and C6, played with the mechanical side of things (tapping, bending LED's etc) and it still does it..I've checked and double checked the layout, the other capacitors, swapped IC's (as I'd mentioned before) and I can't see anything untoward. I'm stumped. It's probably something obvious, but in my defense ;-) I just finished the other bulbdial and it's working fine...any chance I could send the board your way for a look?

Thanks,

Nick

Windell Oskay

My best guess is that there's a damaged LED that's not acting like an LED.  But yes, please contact our shop directly about returning it for examination and repair. 

stocknic

Thanks Windell, I've sent an email...just hope it's not an embarrassingly easy fix that I should have spotted!

Cheers,

Nick

stocknic

Hi Windell....did you receive the board OK? Any idea what was wrong?

Cheers,

Nick

Windell Oskay

We did receive the board, and found that several LEDs had failed-- either not lighting up or lighting up, but somehow connecting two of the LED lines together.  We swapped those out, and it seemed okay, but on letting it run a little longer, we've found that a few of the others are now flickering or otherwise.  And, I must say that we have _never_ seen anything like this before.  (The Bulbdials at our shop are running fine after years...)

We can keep replacing the LEDs until we've got them all, but I'm absolutely lacking any kind of explanation about what could have caused this. Is there anything "unusual" that you might have exposed the circuit to?  (I don't imagine there is, but again, I'd really like to get to the bottom of this.) Can you say what kind of soldering iron you use?  The other solder joints look good, but I am curious if there could have been some electrical damage.

stocknic

Hi Windell, I wish I could give you more info, but as I mentioned I was building this PCB along with two other bulbdial kits and the others went together fine....haven't changed my rig or solder in anyway for many years...Just finished building some more nixie tube clocks with the same equipment too, no issues there either...not sure what to say! My bulbdial is still working after many years too! ;-) Perhaps a PCB solder track short to ground somewhere that's very very tiny?

Nick

Windell Oskay

Well, it was worth asking.  

One way or the other, we'll get you taken care of-- I'm just hoping that we can understand the failure mode, too.

stocknic

Cosmic ray? ;-)

BTW, I use an Edsyn 951SX solder station (or sometimes an AOYUE 968A with SMD rework).

No rush on the PCB....I'd be very happy to hear what's wrong with it (or me!) too.

Cheers,

Nick

stocknic

Hi Windell, any further progress on this?

Cheers,

Nick

Windell Oskay

*At the moment* it is working perfectly, with a couple of asterisks.  We'll be contacting you offline about it.

Windell Oskay

So my best guess as to the root cause: You pressed the bent-over LEDs down to the board *really well,* enough so that the little barbs just below the lens plastic cut through the solder mask, and into the traces below, causing some sort of short circuit.  It may have damaged the IC, or the LEDs-- not sure.  I don't see any other signs that point to a possible cause.  Your soldering job was impeccable, and all of the components *seemed* okay otherwise.  

And again, this is a new failure mode for us to see-- we'll obviously keep an eye out for things like this in the future.

stocknic

Thanks for the feedback Windell. Good news is that the replacement has been constructed and completed without issue, so hooray!

All the best,

Nick