The Type 43, is an audio output pentode that is designed for use in receivers with a series heater chain. It is electrically identical to the IO based 25A6. The valve is rated for use in low power single ended output stages.
Microscope image of the Type designation. The image has a clear outline to the figures with less dense material in the centre of the 3. This is typical of both letterpress and flexographic printing where a raised image is pressed into the substrate. Traditionally we think of these images as having been etched but the evidence suggests otherwise.
The pentode is mounted high up in the envelope.
The three wire grids extend below the anode box. The control grid is wound on copper supports and has a heat radiating fin attached to the top of the supports.
The control grid radiator, side micas that grip the envelope and prevent movement within the glass.
Another view of the top mica and radiating fin.
The classic envelope is 44 mm in diameter and, excluding the UX6 base pins, is 100 mm tall.
References: Data-sheet, 1040 & 1043. Type 43 was first introduced in 1932. See also1932 adverts.
