Glad to finally get this question in front of people who might be able to help. Sorry in advance for the long post; just trying to be thorough for good measure :)
I very recently dove into the circuit-building hobby, specifically Nixie clocks. The PV Electronics kit seemed like a pretty good starting point for someone with undeveloped solder skills, and even less electronics knowledge, to work at expanding both. I would say this has definitely been the case, but it hasn't been without the expected learning curve. I completed the low voltage and high circuits per their directions (QTC clock instructions & diagram pdf <http://www.pvelectronics.co.uk/kits/qtc/qtc_v11a.pdf>) and ran the simple voltage tests across the 5V and 175V portions, all went well. I subsequently added the remaining components, and began the final test to light up a tube. The seconds-place position worked great, just as I'd hoped, but moving to the minutes position didn't work out so well. Plugging the power supply into wall yielded a number of effects, none of them good. -Something going sizzle... -The minutes tube either drawing voltage backward, or cathode-to--cathode, with purple flashes at its lower interior portion (this the same tube that ran fine in the seconds position) -All RGB LEDs which had previously illuminated blue (the default start condition, I assume) were now fully lit to make a violet color (all elements full blast) -Before promptly yanking the power supply after a second or so, I saw all these signs start to fade or draw down (brightness and sizzle) So, the project fried, I discharged all capacitors and set to (more) carefully inspecting my handiwork. I found what I thought was a single tiny solder bridge that may have shorted one of the resistors in series with an RGB LED and fixed it, but I wouldn't think that would cause such theatrics. I assume that there was a short or polarity-swap in the second Nixie socket, which I guess could allow more driving current than desired and cook some things (the transistor at each Nixie that I assume is acting as a control relay, the logic IC controlling those transistors, the MOSFET supplying the high voltage, or the voltage regulator supplying the low) -As best I can tell, the switching transistors for each tube look intact (no obvious burns, cracks, etc.) but I don't think I can test them easily while soldered in place -The anode IC and cathode IC look intact, though again, no way to tell if they are burned internally -I did a resistance check across all capacitors, and they are charging/discharging, though I don't have a great way to measure Faradays (just a multimeter) -All diodes appear to still be resisting current in the right direction -The 5V power supply circuit is still testing good -The high voltage power supply was not amplifying (12V in, 13V out instead of ~175V) The last point suggested that voltage amplifying transistor was shorted and non-functional, so I removed it (it easily broke apart as I did so) and replaced it. The high voltage circuit still reads the same afterwards, as are the fully lit LEDs (no sizzle, though, and only the 'red' is illuminated after removing the solder bridge), and that is as far as my problem solving has carried me. One point worth mentioning, is that the board is attempting to draw too much current, which causes the self-resetting fuse to disengage (the "fading" I saw initially also occurred during this subsequent testing of the HV circuit, but momentarily shorting the fuse lit the LEDs right back up). I'm a mechanical design engineer. This stuff ain't my bag, not yet anyway. But as best I can tell, the logic side of the circuit diagram suggests the 'anode' IC can tell it's not getting 175V and may be lighting the LEDs fully by default (as opposed to those connections being cooked, which I'd assume would cook the LEDs themselves). The 'cathode' IC directly meters the needed juice to the Nixies, so it is possible/likely it was damaged during the high current excursion, but there is not the visible/olfactory signs I'd expect of the distinct sizzling I caused. I don't think the 'anode' IC could be exposed to damaging current from the Nixie portion of the board, unless both layers of switching transistors shorted source-drain (I'd think this would also cause some dramatic results in the 6 transistors involved). So, my theory is that the problem still lies in the high voltage generation circuit...somewhere. I suppose I could blindly start replacing stuff, but I'd like to at least chase the most likely issues first. To anyone who made it this far, and has a suggestion, I salute you. Many thanks, regardless. TCB -- You received this message because you are subscribed to the Google Groups "neonixie-l" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send an email to [email protected]. To view this discussion on the web, visit https://groups.google.com/d/msgid/neonixie-l/7cf1fb99-10ae-4260-9a93-402c3ee04d0e%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
