931 Equasonne Tuning Selector Module:
Also used in models 101, 110, 111 and 301.
View of the tuning selector unit from a 931 equasonne.  The "stringing" of the dial wire is visible.  The upper and lower shielding has been removed to show internal components.  Numbers shown are Sparton part numbers.  This same tuning selector was also used on both the AC and DC versions of Models 301, 591 and 593.  Notice that the third tuning coil has a different part number than the other three coils.  This third coil contains a tap part way along the windings, the other 3 coils do not.  The earlier 930 type of tuning selector differs from the 931 type in that it uses 4 identical coils, but includes an additional tiny fifth coil.
There were two overal types of tuning selector Module used in Equasonne radios.  The first type (of which this is an example) contains no vacuum tubes.  The second type, that was used in the majority of Models contained a socket for a 485 tube, and possessed a four wire cable for integrating this tube to the rest of the Equasonne circuit.

To further complicate things, there are actually two main versions of the "tubeless" type of Equasonne selector.  The "tubeless" selector from the model 931 shown here was the version used in later models.  Earlier models contained a very similar looking but slightly different (930 type) unit.  These two tuners really only differ from each other in two small details.  The earlier 930 and later 931 "tubless" tuners are fully interchangeable.
View of the back of the selector unit showing the antenna and ground binding posts.  On 931 type tuners the posts are spring like in construction.  The antenna wire connects to post A, and a ground wire can be connected to post G.

The RF amplifier circuits of the equasonne cannot be aligned as can those of many TRF radios, as they are untuned.  It is however possible to make minor adjustments to the antenna compensating and equalizing condensers.

The Antenna compensating condenser which can be adjusted with a flat head screwdriver until maximum signal strength is achieved is indicated (ACC).

The three equalizing condensers are not visible with the upper shielding installed.  The adjusting nuts are accessible through the 3 access holes in the top of the shielding.  These condensers are numbered 1 thru 3, with number 1 being the farthest from the tuning drum.  Adjust condenser 3 first, then 1, and finally 2.

Instructions on adjusting all four of these trimmer condensers is given elsewhere in this website.
Front view of the selector unit of a 931 Equasonne.  "Stringing" of the dial wire can be seen.  The metal prong under the tuning drum inserts through a small hole in the end of the RF amplifier and passes on the radio signal directly to the grid of the first 484 RF amplifier tube.  The shared connection to ground is made through a metal plate (not present in photo) that sits under the metal mounting brackets and is held in place by one of the 4 mounting bolts that hold this unit to the wooden board  inside the cabinet.
Problems with the Selector unit
The selector unit should be the most trouble free part of the entire set, possessing no electronics that should be in need or repair or replacement.

The original plastic scale on the tuning drum may have become very fragile over time.  If it is broken or needs replacing, a reproduction scale can be obtained from Rock Sea Enterprises.   The dial scale used in the all the Equasonne models described on this website are the same (Sparton part no. A-4584).  The dial lamp that sits inside the drum is actually part of the RF amplifier unit.

The selector unit contains a few pot metal castings.  Pot metal is notorious, and generally ages very badly, becoming incredibly fragile and often puffing up and splitting like popcorn in the process.  In the radios I have come across, the castings generally seem to age well, however I do have one tuner where the two threaded spools that take up the dial cord have puffed up and cracked so much as to become unusable.

Generally a good cleaning seems to be in order with these selector units.  The bottom shielding box that encases the coils tends to serve as an excellent home for all sorts of fauna!  Be very careful when removing the botton shielding box, so as not to touch or scratch the fine wire on the 4 coupling coils inside.  Unsolder the connector wire that protrudes through the shielding to the long connector prong before removing this shielding. 

A description of how to adjust the antenna compensating and equalizing condensors on the selector unit is given elsewhere on this site.
Pot metal take up spools from the tuning selector.  The spool on the left has not aged quite so gracefully as the one on the right!
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