Here's a manual for it!
https://www.ebay.com/itm/HP-Hewlett-Packard-59309A-HP-IB-Digital-Clock-Operating-Service-Manual/391791021156?epid=1462831819=item5b38908c64:g:WiYAAOxydB1Sk9jC
On Sunday, September 15, 2019 at 6:55:26 PM UTC-7, Kevin A. wrote:
>
> Wow. From the days when HP actually
Yes! That's exactly what happens. The current through the center-tap is the
sum of the anode (segment) current and the grid current. And the peak
current through the filament wires is actually *greater* than just the
current to heat the filaments.
*Tomasz* - As you found out, those VFDs draw
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
