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Electronic Valve - Marconi, Pentode, Type W81, circa 1945 Object Reg. No: ST 028556

Remote contrl pentode, made by Marconi in England.
Possibly similar to Type W81/M.
Metal enveloped valve with non-standard loctal style base
Remains of paper label on aluminium can with glass valve inside
Acquisition Information:
Exchange from P. Thomas, 1972
Discipline: Technology
Dimensions: 74 mm (Length), 37 mm (Diameter)

More information

Tagged with: thermionic electron valves
Themes this item is part of: Engineering Collection, Information & Communication Collection
Primary Classification: ELECTRONICS
Secondary Classification: Vacuum Technology
Tertiary Classification: amplification
Inscriptions: Metal can: W81/Made & patented in England
Manufacturer: Marconi, England, Great Britain, circa 1945


Chris Parry Posted on 01 Dec 2010 4:34 AM
Type W81 is indeed the same as type W81M. Used as RF & IF amplifiers in early examples of the GEC BRT400 comms receiver. The base is standard UK type B8G, functionally equivalent to Loktal/Loctal. Early W81s have a metal spigot. Late ones such as this have a black plastic moulding. Type W81 can be replaced by 7A7, or EF22 in most applications - or by type 7H7 for more gain. Best regards, Chris Parry in Portsmouth, UK.

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