Quote:
Originally Posted by Viewmaster
But I cannot get any sparks. I thought that my feedback coil was wired back to front but if this was so why all the energy and warmth !
As its DC high tension supply rather than 50 hertz, maybe it needs an interrupter to kick it off?
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Hello, with this might rig, you should be getting effects that are spectacular! An established rule of thumb for spark length is L=1.7 *(Sqr root power in)
Where L= spark length in inches
Or about 50 inches with 1kW in. Your two valves there can manage 2kW as a pair but I don’t know exactly if your power supply can support that.
*If you can’t get a break out, it can mean you need more capacitance in your topload or generally a mismatch between the resonant frequency of your tank circuit and the self-resonant frequency of your secondary.
*you need a very good capacitor in the tank. Strontium titanate doorknob types are the best.
*try reversing the phasing of the grid feedback coil.
* try moving the feedback coil closer to the primary, but watch for flashover as huge voltages can appear here when tuning is out.
*Also check and maybe adjust the period of your grid leak circuit. The capacitor here has to be a decent RF power type. Make sure it’s rated 2kV minimum.
*Most importantly, check that you have a very good RF bypass capacitor across the EHT power supply as the RF circuit is critical and without it, nothing will happen. The capacitor should be rated 15kV or higher.
This advice is based on multiple builds over the years with transmitting valves.
Good luck!