SY4307A
Encyclopedia
The type SY4307A is a power output pentode
possessing a similar power ratings, but significantly different characteristics to the far more common type 807
thermionic valve/vacuum tube.
), this type was usually used for the latter.
This tube/valve is a pentode with a 'directly heated cathode', meaning that the cathode consists of an emissive oxide coated filament. These features suggest the SY4307A could predate and is contemporary with, the 807 which is a beam power tetrode, a more advanced design with a more linear transfer characteristic and a more complex 'indirectly heated cathode'.
It is possible to interchange the two with the relatively minor alteration involving the linking of pins 4 and 5 and ensuring the heater supply is "floating". If the heater is supplied from an A.C.
source, linking pin 4 to the centre of that source and the cathode bootstrap minimizes hum pickup.
Two SY4307As were used, wired in parallel, as the output stage, or "final
", in a transmitter constructed clandestinely by the Australian soldiers of Sparrow Force in Japanese occupied Portuguese Timor in 1942. This transmitter became known affectionately as "Winnie the War Winner", named after the British wartime Prime Minister, Winston Churchill
.
Pentode
A pentode is an electronic device having five active electrodes. The term most commonly applies to a three-grid vacuum tube , which was invented by the Dutchman Bernhard D.H. Tellegen in 1926...
possessing a similar power ratings, but significantly different characteristics to the far more common type 807
807/ATS25
The 807 is a beam tetrode vacuum tube, widely used in AF and RF power amplifier applications. The 807 is one of the most ubiquitous and recognizable of thermionic valves/vacuum tubes.-Audio uses:...
thermionic valve/vacuum tube.
Uses
Although the 807 is used for both audio amplification, (usually class AB, and radio frequency amplification in the 1-30 MHz range, (usually class CClass C
The term Class C may refer to:* Class C amplifier, a category of electronic amplifier*Class C , a defunct class in minor league baseball in North America* Class C stellar classification for a carbon star...
), this type was usually used for the latter.
This tube/valve is a pentode with a 'directly heated cathode', meaning that the cathode consists of an emissive oxide coated filament. These features suggest the SY4307A could predate and is contemporary with, the 807 which is a beam power tetrode, a more advanced design with a more linear transfer characteristic and a more complex 'indirectly heated cathode'.
Similarity to 807
If the pinout of the SY4307A is compared to that of the 807 the similarity is striking. All pins are assigned equivalent electrodes with the exception of pin 4, which is the suppressor grid, g3, in this type but in the 807 pin 4 is the connected to equivalent of a suppressor grid, the 'beam plates' and also the separate indirectly heated cathode.It is possible to interchange the two with the relatively minor alteration involving the linking of pins 4 and 5 and ensuring the heater supply is "floating". If the heater is supplied from an A.C.
Alternating current
In alternating current the movement of electric charge periodically reverses direction. In direct current , the flow of electric charge is only in one direction....
source, linking pin 4 to the centre of that source and the cathode bootstrap minimizes hum pickup.
Historical significance
The SY4307A was used extensively during World War II by the Australian armed forces and the example depicted is marked on the Bakelite collar of its base with the "D broad arrow D" commonwealth department of defense mark.Two SY4307As were used, wired in parallel, as the output stage, or "final
Finality
Finality may refer to:* Extrinsic finality* Intrinsic finality* Finality...
", in a transmitter constructed clandestinely by the Australian soldiers of Sparrow Force in Japanese occupied Portuguese Timor in 1942. This transmitter became known affectionately as "Winnie the War Winner", named after the British wartime Prime Minister, Winston Churchill
Winston Churchill
Sir Winston Leonard Spencer-Churchill, was a predominantly Conservative British politician and statesman known for his leadership of the United Kingdom during the Second World War. He is widely regarded as one of the greatest wartime leaders of the century and served as Prime Minister twice...
.