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Radio Broadcast
fig. 5
If the bulbs light, pull the plug out, listening for a click in the loud speaker or phones. W hen these simple tests do not actually show you the way out of your difficulty, a description of the results will be of very great benefit to the Grid Department, or to your local expert in helping you out
lighted, the plate circuit in the last tube is, probably open. This may be additionally ascertained by
Test No. 4. — Pull the phone plug in and out, listening for a click. Change from phones to loud speaker and repeat the test. This will place the difficulty in either the output instrument or within the set. If one pair of telephones give a click in response, it is evident that the difficulty lies in the other. If the trouble is in the receiver proper, and neither phones or speaker work, try
Test No: 5 — Place another tube in the last socket and repeat Test No. 4. No response absolves the tube, placing the blame on an open B batten circuit, with the probability that the phones and speaker are in good condition.
Test No. 6 — This should be in the form of a momentary short, or, better, a voltmeter test across the B batten' posts on the set. If current is indicated, this shows the trouble is within the set; the current from the battery has succeeded in traveling as far as the binding posts. No deflection on the voltmeter or spark, if the voltmeter is not used, locates the difficulty on the battery side.
If tests No. 1 or No. 4 show that there is a plate circuit, that the batteries are O. K., the next test on non-regenerative sets (neutrodynes and stabilized radio frequency) is
Test No. 7 — It is then possible that there are no receivable stations on, which means that they are off schedule or shut down by an sos. More than one fan has decimated his set during the enforced silence accompanying a distress call at sea. Have someone ring your doorbell, or turn on and off your electric light, respectively while you listen for a rough buzz or clicks in the receivers or loud speaker. These will indicate that in all probability everything is O. K., or that the trouble is in the antenna or ground connections. No results or results below normal, suggest the radio frequency circuit is the source of difficulty.
Test No. 8 — With regenerative receivers, those employing detector feed-back and potentiometer or similarly controlled radio frequency circuits, this test will probably precede test No. 7. Turn up the regenerative or "volume" control. The usual oscillations, "plops", or squeal, show that the regenerative detector and audio frequency tubes are O. K. The operator will then proceed to Test No.