unrealdave wrote:... why is the anode always connected to HT +ve in my battery sets?
When heated, the filament or cathode has a special coating that emits electrons, which are negatively charged particles. As with magnetism, like fields repel and unlike fields attract thus, when a positive charge is applied to the anode, the electrons are attracted to it and a current flows. If we introduce a grid between filament/cathode and the anode, a
negative voltage can be applied to control the electron flow through the valve, the more negative it is, the more it repels the electrons and less current flows.
unrealdave wrote:...Is it correct then to connect the -ve of the electrolytic to the anode line and the +ve to the line I consider the earth?
Only if you like big bangs and the prospect of picking out innumerable strands of tinfoil from inside your radio! In a word, no! The positive connection of an electrolytic must always be positive with respect to the negative terminal or at the same potential but
never reverse polarised.
unrealdave wrote:...Why would I get 240v when its all connected up but 120v with no smoothing?

- Rectifier.png (2.68 KiB) Viewed 1900 times
As the AC input rises, the diode conducts and the smoothing charges up to the peak positive voltage. When the input drops, the diode stops conducting and the charge on the smoothing capacitor keeps the voltage constant.
If you remove the smoothing, the diode output will rise up to the peak of the input and then drop down to zero again, where it remains for the negative half cycle because the diode no longer conducts. I assume you have a full wave rectifier, the other half of which repeats the action during the other half cycle. Your meter tries to follow this but effectively only sees an input for roughly half of the time, so it averages this out and reads 50% of the peak voltage.