10-08-2016, 11:22 AM
Rob's circuit shows that the heaters are series connected and need 7.5V. Not the nicest of designs, a live chassis mains/battery set. More or less inherently unsafe. All too easy to get too much voltage on the heaters, especially as the HT and heaters partially share a dropper. Using a capcitative dropper with this set would be tricky as there's a rectifier and smoother caps involved. Cap droppers work fine for pure AC but you can't use AC to heat these valves.
Cap droppers have occasionally been used for heater chains in TVs but diode droppers were much more common. Neither approach will really work with this set. I'd prefer to run it on batteries - the valves will be safer that way and so will you.
Cap droppers have occasionally been used for heater chains in TVs but diode droppers were much more common. Neither approach will really work with this set. I'd prefer to run it on batteries - the valves will be safer that way and so will you.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
