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RADIO INSTRUMENTS V4A

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Top View [33K]Waveband SwitchReaction ControlTuning controlAerial and earth connectionsH.T. battery connectionsHeadphone connectionsValve socketsL.T. battery connectionsFilament current control

  • 1923
  • Wavebands not known.
  • 4 Valves (unknown types)
  • Powered by three batteries.
  • Original cost unknown.
NOTES 1.5V Grid Bias BatteryTypical 20's styling where the radio is looks like a scientific instrument and certainly not something to find on the sideboard of a family home.

The set required three batteries, one for the main H.T., one for the valve heaters (circa 6V) plus a small one used soley to apply a -ve bias to the grid of the valves. This latter battery didn't have to supply much in the way of current and in this set the small battery (about the size of two PP3's side-by-side) is permanently attached inside the set whereas the other two batteries are connected via subtantial brass screw terminals.

This set is a T.R.F. design ; at this time superhets were yet to be sufficiently developed for commercial sale. The set includes a reaction control which is used to rotate a coil so as to vary its alignment (and hence coupling to) the main tuning winding.

The filament supply is connected to the valves via a reostat which, when rotated fully anti-clockwise, disconnects the filament supply. In this state there would be no need to disconnect the H.T. or grid bias batteries since all the valves would be switched off. An advantage of this arrangement is that when the set is switched on, the reostat will be at maximum resistance, this reducing the initial surge of current into the valve heaters. This was far more important with early valves whose filaments operated at higher temperatures than later valves (making the ratio of initial current to steady state current that much higher), and also the heater construction was more fragile than with later valves.

Two very similar sets from the same manufacturer are illustrated in the book "Radio Radio", the sets being the V2A (2-valve) and V3A (3-valve) so I guess this V4A must have had four valves (not necessarily obvious from the four valve sockets as some could have been for plug-in coils).
SERVICE DATA Nope :-(
CURRENT STATE The set is minus its valves. There should also be a wooden lid to cover the set, but only the holes for the hinges remain.
WHERE FOUND The watery skip antique shop for £19

Interior components [35K]Rotating reaction controlTuning capacitorGrid bias batteryFilament control rheostatTapped tuning coilInter-stage coupling transformers
Reaction coil can be seen approximately center top.


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J.Evans 2003
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Last updated
14th April 2003