|TL/12: BBC Versions|
The BBC ordered many TL/12 amplifiers from Leak. To meet BBC requirements, Leak introduced special circuit variations to the TL/12. For example, input transformers were introduced to add a balanced-input for 600 Ohm circuits. Output transformers can vary too, in some cases featuring high-impedance windings for driving the modulation stages of BBC transmitters, and tertiary windings for the feedback loop (as in the TL/25A).
Included here is one circuit schematic for just one of the BBC Leak TL/12 amplifiers (the BBC LSM/8A of 1952). I would like to thank David Porter of the UK for forwarding this to me. He informs me that there were instances of TL/12 amplifiers still being used for transmitter modulation up to the early 1990's!
Above: The heat-shield shown on the BBC TL/12 was a factory
fitted modification by Leak,
as was the input transformer and gain-control.