The 7B5 on a Loctal (B8B) base is electrically equivalent to the 6K6GT on the International Octal base. The valve is an audio output pentode designed for the final audio stage of television and radio receivers. Strapped as a triode it is also rated for service as a frame (vertical) output valve.
Electrically it is identical to type 41 it was also released in 1950 (UK) with a Loctal base under the type number of 7B5E.
Sylvania introduced the Loctal base in 1939 to provide positive holding of the pins in the socket.
This example was made in the USA by Sylvania and supplied to the UK during WWII under the Lease/Lend scheme. In the UK distribution was by Brimar (commercial brand name of STC).
The Sylvania name under the orange overprint.
The Sylvania logo.
The 7B5 is placed on the dome.
The paper sticker on the box gives the Type designation and the price 12 shillings and ten pence.
The Lease/Lend details: maximum price and endorsed by the BVA - to stop profiteering.
The rest of the label. Retail Price Maintenance was abolished in 1964. The practice of setting a minimum price protected UK industry from the effects of lower cost imports. Protectionism leads to reduced manufacturing efficiency and ultimately to the collapse of the protected industry as it is left with only the home market.
The wide glass tube envelope is 29 mm in diameter, and excluding the B8B base pins is 65 mm tall.
References: Data-sheet, 1040 & 1043. Type 7B5 was first introduced in 1949. See also1949 adverts.
