Adjustment of Aerial and Equalizing Condensers, Equasonne Receiver.
SPARTON EQUASONNE MODEL 931
Adjustments of Aerial and Equalizing Condensers, Equasonne Receiver
The Equasonne receiver consists of three separate units, the selector, radio frequency amplifier and power converter.
The selector consisting of four variable condensers and coils, is of the band pass filter type, making four tuned circuits loosely coupled to each other.  The coupling is adjusted so as to give a flat top selectivity curve about 10 kilocycles wide.
The radio-frequency amplifier is a five-stage untuned radio-frequency amplifier with a plate rectifier type detector, using six tubes in all.  This amplifier amplifies approximately equally well all frequencies within the broadcast band.
The power converter consists of the conventional type rectifier and filter system as well as the one stage of audio-frequency amplification.  The power converters are of different construction in each respective model ranging from one power tube to two power tubes in push-pull.
The antenna compensating condenser is located nearest the antenna binding post.  To adjust this condenser a broadcasting station operating on approximately 1250 kilocycles should be tuned in and the condenser adjusted until maximum signal strength is obtained on the speaker.  Another station should then be tuned in on a low frequency and the condenser again adjusted.  It sometimes happens that it will be necessary to adjust the condenser to a point midway between these two adjustments in order to obtain best operation over the entire wavelength range.
The equalizing condensers are immediately back of the 3 tuning condensers nearest the tuning dial.  The third equalizing condenser is the closest to the dial while the first equalizing condenser is nearest the antenna compensating condenser.
The third equalizing condenser should first be adjusted for loudest signal strength using the special wrench supplied by the Sparks-Witherington Company.  Equalizing condenser number 1 should then be adjusted and then condenser number 2.  When making these adjustments, use about 10 feet of antenna wire if a local station is used and the regular antenna if a distance station is used.  A modulated oscillator can, of course be used for supplying the signal strength which will give sharp tuning effects.
These adjustments can be accomplished by pulling the chassis out from the cabinet.  It is not necessary to disconnect any of the connections.
Service Data Measurements for Sparton Equasonne Receiver, Model 931
The Model 931 receiver uses six Cardon tubes No. 484.  These tubes are practically the same as the standard five-prong 27 type tube but having filament voltage rating of 3 volts and a filament current reading of 1.1 amperes.  The power tubes in this receiver are Cardon 182 type tubes, two of which are connected in push-pull.  The Cardon 182 tube is similar to the 245 tube having a standard four-prong base and a filament rated voltage of 5 volts and a filament current of 0.8 amperes.  These tubes can be tested in any regular testing instrument.  The rectifying tube used in this receiver is the standard 280-type tube.
Copyright 1931 by National Radio Institute, D.C.
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