Sparton Equasonne Radios

930 Equasonne Tuning Selector Module:
Also used in model 39, 49, 69, 79-A, 89, 89-A, 99 and 109 deluxe.

There were two overall 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 930 shown here was the early version.  Later models contained a very similar looking but slightly modified tuner (931 type), these two tuners really only differ in two small details.  The earlier 930 and later 931 "tubeless" tuners are fully interchangeable.

 

View of the tuning selector unit from a 930 equasonne.  The "stringing" of the dial wire is visible.

 

 

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 selector units antenna compensating and equalizing condensers.

Inside the selector unit

View of the selector unit from a 930 Equasonne with the bottom shielding removed.  The 4 coils which couple the tuned circuits are visible.  A tiny fifth coil (not visible in this picture) is present in this selector.  The tubeless selector used in later models (301 591, 593, 931 etc) did not include this coil.

Binding posts

 

A view of the rear of the 930 tuning selector unit.  The early 930 type tuning selectors have the two upright binding posts (A, G) visible, in the picture.. Later model tuning selectors  from Models 301, 931 etc. can be easily distinguished from the earlier 930 type as the binding posts are a very different style..

The antenna is attached to the binding post labeled A. A ground wire can be attached to the post labeled G.

The antenna compensating condenser ACC, can be adjusted with a common flat head screwdriver to maximize reception.

The three equalizing condensers are located underneath the top shielding and are not visible in this picture.  They can be adjusted while the shielding is in place by inserting a special tool into each of the 3 access holes labeled in the picture.  Adjust trimmer 3 first, then 1 and finally 2.  Instructions on making adjustments to all of these trimmers are given elsewhere in this website.

 

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 Radio Daze, or from Radiola Guy.
  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 can often age very badly, becoming incredibly fragile and sometimes 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 bottom 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. In some cases, it may be necessary to replace the braided metal wire that turns the dial. Sparton Service Bulletin 9B describes how to do this. Not a lot of sources out there for replacement cables, but Adams Manufacturing does sell the stuff.

A description of how to adjust the antenna compensating and equalizing condensers on the selector unit is given elsewhere on this site.

Pot metal spools

 

 

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!