UK Vintage Radio Repair and Restoration Discussion Forum - View Single Post - Jonell Radio. A cheaper version of the Ace 50.

Mike. Watterson · 20th Jun 2018, 7:34 pm

US AC/DC sets, or USA AC sets with only transformer for heaters, or USA battery/mains tube sets use a -Ve bus bar (a heavier naked wire stood on tags) connected to one side of mains. The chassis is connected to that via a capacitor and the smoothing cap common are not connected to chassis (often have a card sleeve), but to the -ve bus wire.
Some even have a metal case, also connected via capacitor. Just two core flex, often unpolarised.
An RCA I got had an additional dropper fitted for 240V in battery compartment. The larger "World" radios Zenith Transoceanic and RCA and Hallicrafter versions often had a barreter or dropper for 220V to 110V. These are not safe on 220V - 240V. Sensibly the adaptor for one Hallicrafters (S72) was an isolating transformer.
I run the USA battery/mains sets off shaver transformers / outlets in a standalone box.

Obviously any "live" set with no transformer for HT needs suitable modern capacitors for any external connections or capacitors making metalwork be an RF earth.

Didn't some KB sets have heater transformers and direct rectified HT?
Some USA sets with NO transformers, not even heater, are AC only as a voltage doubler is used to give decent HT and that needs AC input.

20th Jun 2018, 7:34 pm	#44
Mike. Watterson Heptode Join Date: Dec 2014 Location: Limerick, Ireland. Posts: 901	Re: Jonell Radio. A cheaper version of the Ace 50. US AC/DC sets, or USA AC sets with only transformer for heaters, or USA battery/mains tube sets use a -Ve bus bar (a heavier naked wire stood on tags) connected to one side of mains. The chassis is connected to that via a capacitor and the smoothing cap common are not connected to chassis (often have a card sleeve), but to the -ve bus wire. Some even have a metal case, also connected via capacitor. Just two core flex, often unpolarised. An RCA I got had an additional dropper fitted for 240V in battery compartment. The larger "World" radios Zenith Transoceanic and RCA and Hallicrafter versions often had a barreter or dropper for 220V to 110V. These are not safe on 220V - 240V. Sensibly the adaptor for one Hallicrafters (S72) was an isolating transformer. I run the USA battery/mains sets off shaver transformers / outlets in a standalone box. Obviously any "live" set with no transformer for HT needs suitable modern capacitors for any external connections or capacitors making metalwork be an RF earth. Didn't some KB sets have heater transformers and direct rectified HT? Some USA sets with NO transformers, not even heater, are AC only as a voltage doubler is used to give decent HT and that needs AC input.