Final result, driving a IV-25 VFD tube!
PCB came back from Osh Park within 2 weeks, and I quickly put it together after getting genuine LP2985 voltage regulators (previous ones from Aliexpress were dodgy):
I left two decoupling caps unsoldered so I can use the pads as reliable test points, and they don’t play a big role anyway. Compared to the original design, I ended up not using the MJD122 darlington transistor and the power transistor you can see above is a ST Microelectronics 2STD1665T4 which is a part that is made exactly for the purpose of building drivers.
I regret not adding a LED to indicate the board is on but oh well… This was just a validation of the design before I add it to a bigger project.
As you can see above, the resulting signal is amazing. Not having noise from the perf board, female headers, etc. etc. makes this truly remarkable. Very happy with the result here!
The board behind the tube is an ESP32 dev board; and each pixel of the tubes is driven by big DIP40 SN75518.
That concludes the “bulding a VFD filament driver series”. Mission accomplished here! I can now start working on the bulk of this VFD project!