I purchased the NK104B HV power supply from here to power some IN-4 nixie tubes. Whenever I turn it on, the 3.3 uF 200 V capacitor explodes. The first few times I used it (for a cumulative ~5 minutes or so) it worked fine. Then, I attached it to an SN74141 nixie driver IC and arduino. I used this to cycle through the digits of the tube; after ~5 minutes of this one of the capacitors began smoking. I turned it off and attached it directly to the nixie tube again, and after a few minutes the capacitor suddenly emitted a large amount of smoke (although the nixie tube stayed on).
I thought this might have been for two reasons. First, I had replaced a missing component (the 200 uF 25V capacitor) in the kit with one of the same specs from amazon. However, I realized the one specified by the kit was actually supposed to be low ESR. Second, I had been running the kit at maximum voltage, and a voltmeter showed something more like 205 V. The blown capacitor was rated for 200 V, so perhaps it was overvolted? I ordered a replacement for both capacitors (getting the exact models on the BoM this time) and tried it again at 160 V. Like before, after a few minutes the 3.3 uF 200 V capacitor blew up (and again the nixie tube stayed on, even though I quickly disconnected the power).
Does anyone have any ideas on what might be wrong? Since the converter worked until I hooked it up to the arduino, I think I might have damaged it. But I'm not sure what components, other than these two capacitors, would be susceptible to damage. Is there an obvious component failure that might be causing overvoltage on the capacitor?
Any idea what might be causing this? Should I just buy a new supply? Thanks for any advice you guys have. Below is a schematic of the HV supply, a schematic of how I hooked it up to just the nixie tube, and a schematic of how I hooked it up to the arduino and SN74141.
This last one is how I attached it to the arduino, except without the coupling capacitor to ground attached to the SN74141 Vcc. Vcc came from the arduino +5V, and I powered the arduino with the same +12V and ground as the HV power supply (both are from a 12V AC adaptor). The power supply had the same setup as the previous schematic, except pin 5 on the supply was connected where it says 180V, and R32 = 10K.