VFDs are basically directly heated triodes. To reach cutoff, the grid has to be at some negative potential in respect to the cathode. It is just easier to elevate the cathode above ground and swing the grids to ground than creating yet another voltage rail. The question is - if the filaments were heated by a transformer with center tap connected to, let's say, 5V, would there be any current flow from or into the 5V rail? The grid + anode current has to go somewhere, after all. It might mean that the elevated voltage has to be low impedance, and most likely - it has to be able to sink current, which standard linear regulators can't do. This is something that concerns me, as I own four ILC1-1/7 and plan to make a clock out of them. Their anode and grid currents are dominant compared to any other circuitry.
W dniu sobota, 14 września 2019 14:22:36 UTC+2 użytkownik Paul Andrews napisał: > > Papers I have read also emphasize the need to bias the filament above the > cutoff voltage of the grid or anode, so I assume if the center tap is > attached to ground, that the cutoff voltage of the anode or grid is > significantly below that? In fact it would have to be below the negative > swing of the AC. It might be easier to connect the center tap to a positive > voltage? See the diagram in the "Cutoff bias voltage" section here: > https://www.futaba.co.jp/en/display/vfdinfo/vinfo_kudo_1.html -- 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 on the web, visit https://groups.google.com/d/msgid/neonixie-l/5050bdef-b0ce-4ddf-a281-4f9aaf277152%40googlegroups.com.
