an attempt to decide whether to use sine or square-wave drive
- though the overall efficiency for this circuit is below 10% - then right now i keep preferring it
- simply coz setting up a consistent pulse drive is a way more complex (unless you have a separate supply to drive the pulse TF from)
- still the peculiarity of the desired output (center tapped winding) sets extra requirements to this drive (you actually can't drive it from the single switch reliably for balanced output or then making it reliable seems at this point more complex ((error prone in practice)) than using a sine-wave drive)
anyway what we got
(winding resistances usually are orders of magnitude lower than the corresponding impedances - so we likely shouldn't care) but here the R.primary much affects a lot of "operationals" that have to fit !optimally&practically for 6LR61 - this in turn requires to redesign the secondary winding -- is quite lengthy error trial chain + in addition to confirm/re adjust in practice (possibly start the design over and over again . . . !!!)
+ did some quick static measurements on . . .
| Name | ИВ-28А | 7-BT-295GNK |
| image |  |  |
| Gate voltage | +9V | +9V & *more |
| Anode voltage | +18V | 2× +9V & *more |
| Filament current DC-driven to neg. from GND | 25÷28mA | 52÷62mA |
| Anode brightness adjustment ► increase voltage for edge segments ◄ | not required for parameter values shown above | required by unknown factor ► required less for gate , anode voltages *exceeding the ones shown above |
if you increase the AN GT voltages the filament feed may be lesser but there seems to be a threshold A-G voltage and filament power starting from where the fade left/-right is reduced and the seeming symbol brightness does not much increase
also - when i experimentally found the FUTABA's operating parameters i didn't expected so high filament current so i had to reduce a lot the gate/-anode voltages to get their apx. min./-normal values -- what was studied is that while the anodes did glow most bright at AN set to 27÷36 V (gate same or 9V less) then going up from there they seemed to start dimming again ?? !!!
[Eop]
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