Protect your device by adding this to the input. Reduces noise, spikes and protects the NCH8200HV. The HV module is sensitive to spikes. Wall-wart power supplies are not all created equally. No failures since adding - had a couple nixie clock failures with the NCH8200HV before doing this. Jeff -------- Original message --------From: 'Richard Scales' via neonixie-l <[email protected]> Date: 2/15/26 11:15 PM (GMT-06:00) To: neonixie-l <[email protected]> Subject: Re: [neonixie-l] HV Power Supply failues 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 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? - RichardOn 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 100-230Vebay.co.ukOn 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. -- 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. -- 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. -- 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/6992b40b.050a0220.89ccd.137f%40mx.google.com.
