Murphy Radio Model A4 From 1933

For 1933 Murphy introduced the model A4 (and derivatives D4 for DC mains and battery set B5). This A4 was an AC Table superhet costing £14.10.0. It was available in a Walnut cabinet inlaid with rosewood designed by R.D.Russell. This set included a high quality back (shown below left), rather than the hardboard seen on the A3. It can be noted that the wood frame has been stained and cloth provided for ventilation. A metal plate is provided on the back and the chassis giving the model and serial number information. A paragraph on page 5 of the Murphy Technical Notes booklet for the receiver informs service engineers that care should be taken to ensure the same chassis is returned to the correct cabinet if two or more receivers are dismantled at the same time. The booklet warns that tuning calibration may be compromised if cabinets are swapped as the cursor remains in the cabinet and not on the chassis. This seems somewhat unlikely though since a greater margin for error would surely result from the position of the chassis itself even in its original cabinet. Murphy themselves appear to realise this since the same warning appears a year later in the A24 Technical Notes, but the reference to tuning accuracy has disappeared. The insert picture (below right) shows the control knob fixing method for the receiver, which was unique to Murphy. Right from the early days Frank Murphy pursued excellence in quality of build, even if it meant having parts made especially. Most manufacturers of the time fixed their control knobs with a small grub screw, which had the disadvantage that the grub screw became “chewed up” and difficult to remove after a while. However Murphy’s method of using a threaded nut securing the knob meant that all the knobs could be removed and refitted speedily without the use of a screwdriver, (providing the securing nut was not lost!). The major disadvantage was that all the controls required specially threaded shafts, which made for difficulties when fitting replacement parts. The idea was discontinued during 1937 and Murphy went over to the more usual grub screw fixing. Murphy was noted for a different approach to advertising, and an advertisement run in 1933 for the A4 and A8 receivers epitomises this by using unemployment as the reason to buy. It listed several observations on the nature of unemployment and how the purchaser could potentially help by buying a set now. For example one line from the ad reads “There is no point in waiting if you want a Murphy set, for we will bring out no new models nor will we reduce our prices during 1933” The valve line up used was AC/PEN, AC/SGVM, AC/HL, AC/PEN, 1807.

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