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In the R. B. Lab
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7. Negative results from Test No. 8 show a fault in the regenerative tube or tubes or in any of the audio stages except the last, which Tests 1 and 4 proved O. K.
Test No. 9 — Tap the bulbs with a pencil, moving progressively toward the antenna connection. This generally means from right to left: second audio, first audio, detector, etc. No ring will be heard in the loud speaker when the fault}' tube or stage is reached.
Test No. 10 — Changing tubes will almost always eliminate or define the bulbs as the source of difficulty.
Try all these tests when your set is working, immediately when the trouble is discovered if possible, in order to acquaint yourself with the response you may expect from a working receiver.
BUILDING YOUR OWN LAB
WIRE your lab. with an eye for convenience in testing and operating more than one receiver in different parts of the laboratory. The arrangement developed in the R. B. Lab can be enlarged or reduced to suit individual convenience.
Filament and plate batteries are centrally located with charging apparatus, and are wired to the benches using colored wire, often called "code wire. "
Six outlets are desirable, which provide for the connections to as many receivers or test apparatus. Seven wires are used. Two differently colored heavy stranded wires carry the A battery current. Four No. 18 annunciator wires of variegated hues, provide plus B battery from 22 J to 140 volts. The negative B is connected to positive A on the battery table. The seventh wire connects to an outside antenna which may be disconnected by a switch at each of the six outlets.
One hundred and ten volt lines are run in metal moulding along the edges of the benches with similar outlets. The moulding itself affords the ground. The moulding should be installed according to underwriter's requirements, who, however, have no jurisdiction over the other wiring.
If desired, fuses, switches, and meters (volt, ampere and milli-ampere), can be installed at the batten table. Several photographs taken in the Lab. depict the utility of this arrangement.
FIG. 6
Tap the bulbs and listen for the usual ring. A ring from any of the r. f. or detector tubes shows that the audio amplifier is O. K.