The 1H5GT is a dry battery diode triode for receiver use. The 1LH4 is the same valve but on a B8B base. In a TRF receiver the diode would provide AM signal demodulation and the high μ triode would be the first audio voltage amplifier.
Normally the Glass Tubular (GT) valves are made as short as practical and our Sylvania 1H5GT is 15 mm shorter.
The lower box screens the diode anode. The anode is the rod near the right side of the screen box. In the centre is the filament support. The single strand filament passes through the central mica sheet and into the triode at the top.
The supports on the right are for the filament. The lower rod is secured in the pinch and welded to it is the longer support that is topped by the spring that maintains filament tension.
Here the control grid can be seen to connect to the top cap. The thin wire spring holds the filament in a closed loop.
The lower screen box with the diode anode rod within. The base of the filament can be seen to be oxide coated.
The wide glass tube envelope is 30 mm in diameter, and excluding the IO base pins is 85 mm tall.
References: Data-sheet, 1040 & 1043. Type 1H5GT was first introduced in 1940. See also1940 adverts.
