Useful valve base adapters, vintage to modern.
I find these very useful. They are B7G valv-holders inserted into either B4 of B5 bases taken from defunct 2Volt valves. The centre spigot is removed from the B7G valve-holders. I 6ba threaded spacer is bolted into the base from underneath with a countersunk bolt. The B7G valve-holder is mounted in an acrylic ring that is slightly bigger than the B4 or B5 base. Each adapter has a dropping resistor inserted in the positive filament lead to allow the chosen 1.4V valve to run on the 2 Volts normally required by vintage wireless sets. In the case of the B5 adapter, the centre pin is used, so the B7G valve-holder is secured by two 6ba threaded spacers under the two normal valve-holder securing holes. What would have been the anode cap of a screen grid valve, is taken to a terminal on the side of the B4 base. In the B4 triode adapter, the screen grid of the B7G valve is strapped to the anode, thus running it as a triode.