WIRING THE SET

Hawke's Bay Tribune, Volume XIX, Issue 282, 13 November 1929, Page 9

WIRING THE SET

When wiring the set use fairly heavy gauge wire, as this has less resistance. Sixteen for eighteen gauge wire is excellent for the purpose, and it is very rigid. All wiring should bo perfectly rigid, as signals are liable to "waver” when the wiring vibrates. It is not so important that tno audio wiring be of bus-bar, and flexible wire may be used here. In all cases it is desirable to use soldering lugs. Solder all joints, and use little or no rosin, as they may cause poor connection. Where the constructor decides against the use of soldering lugs the end of the wire should be twisted round the terminal to which it is to be fastened in a clockwise manner, as otherwise, when the holding screw is mounted, the wire will be screwed off. Where metal bases, shields, etc., are used, leads that arc taken through holes should be encased in spaghetti. If this is not done, the rnbbed or insulation round the wire is liable to become worn, and cause a short, since the metal is earthed, and sometimes connected to ono sidq of tho filament. It is a mistake to test cut a receiver, without checking over wiring. The quickest way to du this is to connect up the "A” battery first and see if the valves all light. If the valves are of a type whose filaments do not visibly glow a voltmeter should be placed across the filament terminals of each valve socket in order with als of each valve socket in order to seo that each valve is being supplied with necessary filament voltage. If everything is in order, the two audio valves (and the r.f. valves, if these are being used) should be removed, end the "B” and "C” voltages applied. There will only be one valve in the set, so that this can be tried in each socket. Naturally, a cheap valve, or ono whose emission is practically useless, can bo used fqr the test. If the valve continues to behave normally, then the other valves can bo plugged in, and tho aoria) and earth attached. If the receiver doos not function properly place the aerial to the grid coil of the detector stage. If reception is now 0.K., yon will know that the trouble is in the r.f. stage. If reception is still "off” com nect the phone terminals to the plate terminal of the first audio valve socket and to B plus 90 volts If receptoin is 0.K., the trouble is in the last audio stage, but if reception is still poor connect the phone terminals across the primary of the first audio transformer. If reception is 0.K., then the trouble is in tho first audio stage. If still no signals are heard, or the signals are poor, the trouble is in the detector stage itself. In this way every stage of flic receiver is tested. It is a good idea to use n torch bulb in series with tho P. negative lend, as then nny short or wrong connection that would ordinarily burn out the filaments of the valves will merely blow the torch bulb. Tn order to test the B plus connections of tho amplifier the phonos or speaker should be plugged in. A loud click should bo heard each time this is done, and n similar or louder click should ho heard when any of the B plus voltages are adjusted.