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GMB · 30th Jul 2018, 10:39 am

A capacitive dropper alone for a series chain with HW rectified HT is a disaster unless the HT current is massively less than the heater current.

I tried knocking this about in a circuit simulator and it looked to me that it was hard to get a viable solution, so I think the FW bridge to even out the cycles is absolutely necessary. Even then there is a problem of waveform distortion generated by the HT so a little care may be needed to get the right heater power rather than the right peak voltage.

I would start by measuring the HT current and then either using a circuit simulator or building a little testbed to try some experiments before you go for the real thing.

The bridge will make it a true live chassis set of course so there absolutely has to be no accessible metal (don't forget aerial and grub screws).

30th Jul 2018, 10:39 am	#2
GMB Dekatron Join Date: Aug 2003 Location: near Reading (and sometimes Torquay) Posts: 3,094	Re: Cap. dropper + full wave bridged set A capacitive dropper alone for a series chain with HW rectified HT is a disaster unless the HT current is massively less than the heater current. I tried knocking this about in a circuit simulator and it looked to me that it was hard to get a viable solution, so I think the FW bridge to even out the cycles is absolutely necessary. Even then there is a problem of waveform distortion generated by the HT so a little care may be needed to get the right heater power rather than the right peak voltage. I would start by measuring the HT current and then either using a circuit simulator or building a little testbed to try some experiments before you go for the real thing. The bridge will make it a true live chassis set of course so there absolutely has to be no accessible metal (don't forget aerial and grub screws).