The Combination Receiver

Radio Record, Volume II, Issue 43, 10 May 1929, Page 31

The Combination Receiver

Adding an Extra Stage (CORRESPONDENTS have been successful with this receiver, and we have been asked how another stage may be added. ‘This is quite a simple operation, but to make a first-class job the receiver should be dismantled and made up after the layout of the twoyalve receiver. If, however, this is not intended, the following short description will be of value to those who want merely to add another stage to the existing set. All that is necessary in the way of components is a transformer, a valve socket (and valve), another "B" and a "O" battery, 9 volts or two 4} volt C’s. Take a baseboard measuring 6in., x 4in., and place the transformer and the valve socket close to one another. Place this board at the back of the existing set. Arrange the transformer so that it will be almost opposite the valve socket of the "Combination" set, but with its axis at right angles to the axis of the transformer now in use. Turn it roynd so that "B" plus and "P" are facing the assembled receiver. The valve socket is to the left of this, with "P" and "G" facing the transformer. Serew these into position. Extend the terminal strip to allow three more terminals, "C-1" and "C-2" and "B plus 2." #Discon-

nect the "F’ terminal of the valve socket, which is connected to the jack, connecting it (the terminal) instead to "A" plus. The wire so disconnected is taken to "EF" plus of the new valve socket. Take the other "I" terminal of this socket to the terminal of the rheostat which connects directly with the valve, If the valve is inserted now (with the plug in) and the rheostat turned on, it should light, indicating that the connections with the filament, at least,. are corrett. Lift the connection between the R.F.C, and jack number 2, taking the lead from the choke instead to "P" of the new transformer. Connect the vacaney so made at the jack to "Pp" of the new valve socket. Connect to "B" of the transformer to the voltage now applied to the jack. This point of the jack now is joined to the highest "B" plus voltage available. Connect negative of one "RB". battery to the positive of the other and the free negative to the binding post "B-," The "B" of the transformer will require from 223-45 volts. The last stage (to jack) about 90 for Satisfactory volume and quality, though it may be reduced to 45. Connect "G" of the new transformer to "G" of the new valve socket, Remove the connection existing between the rheostat and "Q-" of the transformer in the original "Combination" set. Take this instead to "C-" 4; (a new battery) (or to C-1 and thus to the battery), and connect its positive to "B-" "Take another 44 battery, connect the positive ta the negative of the "C-1" battery, and its negative to "C-2" on the terminal strip. Connect this with "C-" on the new transformer.