▼ Menu

    
Extras ▼

This ML4 looks to be an early example as it is enclosed in a balloon envelope. We have another ML4 in the later classic envelope.

Although sometimes listed as a triode output valve, the ML4 was the definitive descendent of the famous (or infamous) Type KL1 of 1926 and was primarily a professional and military type, little used in domestic radios.

The ML4 was quite widely used as an RF oscillator, as a single-valve phase splitter, and as a driver for larger valves.

As close a view as is possible with the Olympus E20 plus 4 dioptre lenses.

The mesh anode, grid, cathode tube and heater are all visible.

The Marconi Valve logo is etched into the envelope as is the BVA logo.

This close-up was taken with a new Nikon D80 camera. The electrodes are fully revealed.

The balloon envelope is 50 mm in diameter and, excluding the B5 base pins, is 105 mm tall.

References: Data-sheet, ¹⁰⁴⁰ & ¹⁰⁴³. Type ML4 was first introduced in 1929. See also 1929 adverts.

Pin Connections

Absolute Maximum Operating Conditions^¶

Thanks to Frank Philipse for supplying the above PDF datasheet.