13-02-2014, 02:45 PM
An autotransformer would be a good option, assuming there's the space for it, but finding a source for one could be a problem. As far as the caps go, motor-run quality types are in my opinion ideal but other good quality and well rated caps should serve OK. Motor-run capacitors do tend to be bulky. I fitted a capacitive dropper in a small Cameo table model receiver and also one in a Little Maestro to replace a line cord. Both very successful, both using motor-run caps.
Also perhaps worth considering is the use of a wattless dropper, i.e. a diode in series with the heater chain and backed up with a wire-wound ballast resistor. Advantages include less heat generation and a physically smaller ballast resistor when compared to a standard dropper. You need to pick a reliable diode, though!
A wattless dropper was used for the heaters of the Thorn 1400 monochrome TV series. It was a BY126 and regularly failed but on failure it caused field rolling, so rendered the set unwatchable until repaired. The probable moral might be: don't use a BY126...
Tony
Also perhaps worth considering is the use of a wattless dropper, i.e. a diode in series with the heater chain and backed up with a wire-wound ballast resistor. Advantages include less heat generation and a physically smaller ballast resistor when compared to a standard dropper. You need to pick a reliable diode, though!
A wattless dropper was used for the heaters of the Thorn 1400 monochrome TV series. It was a BY126 and regularly failed but on failure it caused field rolling, so rendered the set unwatchable until repaired. The probable moral might be: don't use a BY126...
Tony
