Simple PSU for a few valves

[glowinganode]

The only other point I will stress is the importance of thoroughly 'soak testing' the finished item on full load before declaring that the item is Fit For Purpose. This is particularly relevant when solid-state devices are employed, since Vbe junctions (and similar - like Zener diodes) can vary substantially at elevated temperatures compared to the 'nominal' 25°C.

Al.

Also a failure of the series regulator or control circuit of a stabilised power supply can lead to the full un-regulated voltage appearing at the output terminals.
Take it out on a lamp bulb for a few hours first.
Rob.