I still think the capacitor coupling will work as long as you use an AC signal to modulate the Z-axis. Putting a DC level-shifter into the circuit that needs to isolate 1000 volts is going to require some very careful design. From what I can see, the time-constant for the Z-axis is pretty long (around 100msec ??), and it's very likely whatever you are displaying is much faster, so DC coupling isn't needed.
An op-amp circuit driven from TTL-level can easily translate from 0-to-5volts to -10 to +10 volts (20V p-p per above target), for example, and that can hook directly to the Z axis jack. Basically, a gain of 4, with an offset of 2.5V if your TTL-level swing the full 0-to-5, though 7400 series TTL devices typically drive out 4V, so a gain of 5 and an offset of 2.0V. LTspice is a good way to simulate your design before building it. The nice thing about inverting OPamps is that the (-) input is already a summing point, so adding the offset is trivial. Thinking about it more, you might not even need an offset. It functions the same as a contrast control, though I dont see such a control on the schematic. Having adjustable offset wont hurt if you dont need it, but not having it if you do need it means another round of circuit changes. On Wednesday, November 5, 2025 at 3:58:38 PM UTC-8 Tom Katt wrote: > On Wednesday, November 5, 2025 at 5:59:08 PM UTC-5 gregebert wrote: > > If you have a very-high impedance voltmeter, you might want to check the > voltages while the CRT appears "normal". I suspect you will see notable > differences between your measurements and the schematic. > > > Yeah - I learned the hard way many years ago working on tube amps that > normal meters and tube voltages don't mix well. I may try the 10X resistor > method, if only to compare ratios and not worry about exact accuracy. > Thanks for the suggestion. > > And yes - the goal is to achieve ttl level signal control, so the > capacitor arrangement needs to go. I've seen a few examples of using > transistor switching, but the trick seems to be getting a manageable > potential difference of maybe 40V to be able to sneak in an optocoupler. > -- 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/1178684a-8916-4102-97c0-ff620c84a3cdn%40googlegroups.com.
