09-12-2021, 09:49 PM
OK thanks for that. Not sure why but I tend to look at peak levels as I seem to always work on voltage swings such as the anode voltage swing etc. So I may be able to use a smaller transformer core then I am thinking???
Anyway what I was thinking is that I have a 220 V primary transformer with two 24 Volt secondary windings, so I can wire them up to give 48 Volt output in normal rms values it is normal 40VA transformer.
If I wired the frame scan coils across the 48 Volt section and the 220 Volt primary between EL84 anode and 250 Volts HT, I was thinking that to get my 50 Volts peak to peak I would need a voltage swing on the anode of 230 Volts, if the flyback voltage manages to get the anode Voltage above HT as in the line drive then I could be working with an anode swing from 135 Volts to 365 Volts even though the sweep rate is 12.5Hz the flyback time is the same as the line stage at 0.23mS. Hence hoping I still get some higher voltage on the anode.
If it does show some promise I will then look to winding a transformer for it. If it shows no promise then I may have to look at using the transformer to provide a + /- 25 Volt spilt rail supply using a valve/semiconductor hybrid circuit to drive the scan coils between rails to get the required swing.
The last option that I do not think would work, was to wind some more frame scan coils with lots more turns but finer wire, getting the peak current down into the 15mA range, this would require two scan coils of approx 11,000 turns each of 38awg wire and the physical size of the coils could be prohibitive for me to hand make. The total resistance would be around 9.4K ohms and online calculators suggest the total inductance would be 23 H !
Think it is time to play over the next few days.
Adrian
Anyway what I was thinking is that I have a 220 V primary transformer with two 24 Volt secondary windings, so I can wire them up to give 48 Volt output in normal rms values it is normal 40VA transformer.
If I wired the frame scan coils across the 48 Volt section and the 220 Volt primary between EL84 anode and 250 Volts HT, I was thinking that to get my 50 Volts peak to peak I would need a voltage swing on the anode of 230 Volts, if the flyback voltage manages to get the anode Voltage above HT as in the line drive then I could be working with an anode swing from 135 Volts to 365 Volts even though the sweep rate is 12.5Hz the flyback time is the same as the line stage at 0.23mS. Hence hoping I still get some higher voltage on the anode.
If it does show some promise I will then look to winding a transformer for it. If it shows no promise then I may have to look at using the transformer to provide a + /- 25 Volt spilt rail supply using a valve/semiconductor hybrid circuit to drive the scan coils between rails to get the required swing.
The last option that I do not think would work, was to wind some more frame scan coils with lots more turns but finer wire, getting the peak current down into the 15mA range, this would require two scan coils of approx 11,000 turns each of 38awg wire and the physical size of the coils could be prohibitive for me to hand make. The total resistance would be around 9.4K ohms and online calculators suggest the total inductance would be 23 H !
Think it is time to play over the next few days.
Adrian
Learning as I go!
Youtube EF91 Valve
Youtube EF91 Valve
