01-12-2016, 09:26 PM
Trevor has explained clearly that an additional diode is required in order the capacitive HT dropper will work. The extra diode is essentially a DC restorer and is wired so that the cathode is connected to the low potential end of the capacitor and the anode goes to chassis potential.
So it follows the AC waveform "sits up" above ground potential. Without the diode the anode of the rectifier will be hit with only DC pulses.
Actually if a 25Y5 or 25Z5 rectifier valve can be found then the classic all thermionic solution could be realised. These valves were designed for voltage doubler power supplies.
www.radiomuseum.org/tubes/tube_25z5.html or www.radiomuseum.org/tubes/tube_25y5.html
Picture of the reassembled set. The metal escutcheon can come into electrical contact with the chassis metalwork so before the job can be signed off something will have to be done about that.
Geordie McBoyne.
So it follows the AC waveform "sits up" above ground potential. Without the diode the anode of the rectifier will be hit with only DC pulses.
Actually if a 25Y5 or 25Z5 rectifier valve can be found then the classic all thermionic solution could be realised. These valves were designed for voltage doubler power supplies.
www.radiomuseum.org/tubes/tube_25z5.html or www.radiomuseum.org/tubes/tube_25y5.html
Picture of the reassembled set. The metal escutcheon can come into electrical contact with the chassis metalwork so before the job can be signed off something will have to be done about that.
Geordie McBoyne.
