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 <[email protected]> wrote: > > > On Mon, Oct 27, 2025 at 4:31 PM Mac Doktor <[email protected]> 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 [email protected]. To view this discussion, visit https://groups.google.com/d/msgid/neonixie-l/CAArLthczeXYLQnthL6gLGVEt%3DsTB1P%2B%2BfOzE-bRh82g2gZEmtA%40mail.gmail.com.
