Re: [neonixie-l] Re: CRT "Scope Clock" - Power Supply Question

[padlernpedler]

Tom, Can you post a link to the eBay listing for the 3RP1A tubes?  I was not able to find it searching with the “I” or “1”, looking in both current and completed listings. Thanks, Randy On Oct 28, 2025, at 6:15 AM, TomJ <tomkat...@gmail.com> wrote:  Forgot to mention - if anyone else is considering a crt clock project, brand new Chinese 3RP1A tubes are available from US sellers on eBay (3 for $85 shipped).  But they are listed with the letter "I" instead of the numeral "1" - the eBay search doesn't pick up on that, so they are easily overlooked.  I think these are the same ones that Sphere used to sell. On Tue, Oct 28, 2025 at 6:07 AM TomJ <tomkat...@gmail.com> wrote: On Mon, Oct 27, 2025 at 4:31 PM Mac Doktor <themacdok...@gmail.com> wrote: Note that over at the GeigerCounters group talking about building negative HV power supplies can get you banned. A couple of people found that out the hard way after having been warned. The -900V supplies in Geiger counters are grandfathered in, of course, and the currents are very low. Certainly, the voltages involved are no joke and can be lethal.  CRT voltages typically are very low current as well, but I suspect still very dangerous.  Though it seems a bit  nanny-state' to ban legitimate scientific discussions - you can just as easily discover mortality working on your car or a home appliance. In any event, I also received a very informative email from the gentleman at Sgitheach...  My understanding is that the crt tube doesn't really care - it comes down how you want to design your circuit.  Having the high potential at the cathode makes the deflection circuit easier to implement because the voltages are lower.  BUT, if you desire to incorporate some kind of intensity modulation or Z axis, you now have to manage that end with high voltages.  The end result from a performance perspective will be the same.   Thanks for the insight! -- 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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/CAArLthczeXYLQnthL6gLGVEt%3DsTB1P%2B%2BfOzE-bRh82g2gZEmtA%40mail.gmail.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 neonixie-l+unsubscr...@googlegroups.com. To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/118EBFC9-49A0-49DB-8224-32380BEE58FF%40gmail.com.