The Screen-Grid Booster

Radio Record, Volume II, Issue 7, 31 August 1928, Page 28

The Screen-Grid Booster

| pete 7 erereperwne Success. and Otherwise N Auckland reader having made inquiries regarding the construction of the booster, writes as follows: "Without waiting for a reply to my last’ queries re booster attaching to five-valve, I am enclosing further queries, as I have made booster, and will. state results. My friend also made. one, and’ has attached it to a four-valve circuit he built himself. similat.t6 a Browning-Drake, and gee! it, has proved beyond expectations. He never had the Japs. or Americans before, and now -he has had two of each on loudspeaker, and the small stations in Aussie he now hears on speaker. Well, you have to hear it to believe it, and. three degrees will tune them ut. I came straight home and started mine."

Our correspondent then proceeds to state that so far his booster has not functioned when connected to his fac-tory-built receiver. Unfortunately, some constructors have bad luck or adverse circumstances of some. kind. It appears to be inevitable with any circuit that is published. In the majority of cases the trouble may be caused by a "resin" soldered joint or some equally simple matter, bad contact on valve legs, coils, ete. Then there is the valve itself. This should always be carefully tested for contact between plate and screen and. screen ‘and control grid in the case of the 222. Some constructors, of course, make considerable alterations in the lay-out, components, etc, and where _ the screen-grid valve is concerned, this is eertainly risky. "3 As a rule it is wise to place a 2 mfd. condenser across the B battery, and also across the detector voltage, in order to minimise any chance of feedback through the battery, which the H.F. choke is also used.to prevent. a