Hello,
I had a number of NCH8200HV failures though specifically, this was when I was using a 12V power adapter, I have many more boards using a 5V supply and none of these have failed. I went straight to the designer who took a look at my board and came up with an answer. l *Root Cause:* Catastrophic MOSFET (NCH8200HV) failure observed across all modules. l *Power Delivery Concerns:* The 12V input bypasses critical bulk capacitance prior to distribution. Current PCB layout lacks immediate electrolytic buffer post power input l *Critical Design Recommendations* 1. *Capacitor Placement Protocol:* 12V rail must implement bulk electrolytic capacitor (≥470μF) within 10mm of input connector. Since then I have added a 470uf electrolytic as suggested and have had zero issues. What input voltage are you using: 12V, 5V, something else? - Richard On Sunday, 15 February 2026 at 11:58:25 UTC Max DN wrote: > Yes, I figured out electronics and windings of the transformer as I wanted > to embed it in my nixie clock design. Yes, the neon is just for fun, as an > indicator that HV is on. > > In my experience 8200 can take 30ma but not for long as the transformer is > very small and gets hot (I may be wrong). I think that even if you are only > using 13ma, the peak current (and in-rush current especially at start up > matters so much). If you have a way to check that, you’ll see. If you don’t > have an oscilloscope, try to use a power bench supply and limit the current > to, say 50mA. It’s a cheeky way to test peak current at start-up, not > accurate but gives you an idea. The power supply will enter into an > overcurrent mode, at least for a few seconds until the current stabilises > within the transformer. There are ways (hardware and software to minimise > in-rush current, but it’s not very simple and requires plenty of testing). > > > > On 15 Feb 2026, at 11:45, 'JBro63' via neonixie-l < > [email protected]> wrote: > > Thanks. They look similar in output to the 6300 but that would need a new > PCB :( > Curious what the neon is for? Power indicator? > > The 8200 is rated for 30ma - I measured 9ma on the prototype when it's > running 4 tubes, 13ma for 6 tubes so it should be within limits. > > On Sunday, 15 February 2026 at 11:19:34 UTC Max DN wrote: > >> You must have acceded peak current and the mosfet is gone. If they are >> both gone, no point repairing or replacing with same HVPS, it’ll happen >> again. >> >> If interested, I have a much more powerful power supply for sale here: >> High Voltage DC Power Supply Nixie Low Noise Audio Tubes 3.7-15V to >> 100-230V <https://www.ebay.co.uk/itm/276921910331> >> ebay.co.uk <https://www.ebay.co.uk/itm/276921910331> >> <https://www.ebay.co.uk/itm/276921910331> >> >> >> >> On 15 Feb 2026, at 10:54, 'JBro63' via neonixie-l < >> [email protected]> wrote: >> >> Hi all, looking for insight in to PSU problems. Have had two NCH8200s >> fail very close together after only a few weeks of use. >> >> In December, I finally got round to building four IN-12 4 tube clocks >> using a new PCB and some leftover tubes and drivers. They are driven using >> a K155ID1 for each tube (no multiplexing) and MJE340 for the INS-1 colons. >> Current limiting resistor is 18K. Each tube anode has a PC851 optocoupler >> to turn the tube off if no presence is detected. >> >> My previous IN-12, IN-14 & IN-18 clocks use the 8200 or 6300 and are >> still going strong. They are driven using HV5530s. >> >> Both 8200s have gone full short across the input. Anything about the >> K155ID1 / PC851 that is harsher on a HV supply? Anything I can check for >> with a scope? >> >> Thanks >> >> -- >> 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 view this discussion, visit >> https://groups.google.com/d/msgid/neonixie-l/a93fbd9d-36aa-4791-bffa-54f7d2514cdfn%40googlegroups.com >> >> <https://groups.google.com/d/msgid/neonixie-l/a93fbd9d-36aa-4791-bffa-54f7d2514cdfn%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> >> >> > -- > 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 view this discussion, visit > https://groups.google.com/d/msgid/neonixie-l/513d8a2a-cb3e-473e-a91f-45e6d50bb56cn%40googlegroups.com > > <https://groups.google.com/d/msgid/neonixie-l/513d8a2a-cb3e-473e-a91f-45e6d50bb56cn%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > -- 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 view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/2fe0e94c-244f-494b-938c-db201d6fdf50n%40googlegroups.com.
