ULTIMATE SG4 'SCREEN GRID 4' (1928)

The Ultimate SG4 was manufactured by Radio (1936) Ltd in 1928, production ran for about 3 years.

4-valve multi-band model (using plug in coils for different bands) using the (then) awesome new technology of a screen grid output valve. Initially battery powered, a 230V AC version was added to the lineup in 1929.

Reportedly designed and built by Radio Ltd's famous design engineer, Reginald "Jack" Orbell, who bought it with him when he came to work at Radio Ltd in 1927.  Production started in 1928, with around 200 produced in that year.

The model ran for a few years, gaining cosmetic improvements over that time, with later models having an updated dial.  Internally there seems to have been constant improvements / changes with several different chassis layouts seen - including one disc-style dial (while most were drum-dials).

The AC power pack that was made available in 1929 was manufactured by the Sexton Radio Co. (See Golden Age of Radio, p69)

Ultimate Screen Grid 4 from 1927-30ish

1928 Ultimate SG4

1928 Ultimate SG4

1928 Ultimate SG4

Valves (4):

Chassis Notes(most schematics can be clicked to download a full size version)

All-wave TRF set - plug in coils

Reportedly the early circuit:

1928 Ultimate SG4

Reportedly a later circuit:

1928 Ultimate SG4

Coil Wiring:

1928 Ultimate SG4

General Construction Notes for Radio (1936) Ltd: Early Radio Ltd. schematics did not show the models, just the year, valves and bands, so some sleuthing is required to find the right one.

Early 30's Ultimate models with three digit model numbers indicated both the number of valves in the set, and the price it retailed for - for example, the model 856 was an 8-valve radio which retailed for $56 pounds. The equivalent Courier models were reversed, so an Ultimate 856 was a Courier 568 (theoretically, at least). This was the Auckland price though, and often the sets would retail for 1 or 2 pounds more in other centres, presumably to cover the freight cost of moving them around the country from the Auckland factory.

Note the use of old resistance terminology on older schematics: ω means ohms and Ω means megohms.

Some 1936-onward 3-letter chassis codes vary the last letter between brands, for example:
BBU - Ultimate model BB
BBR - Rolls (and Golden Knight) model BB
BBC - Courier model BB
All use the same chassis.

Golden Knight, Courier and Rolls appear to use the same copper-painted chassis while Ultimate chassis' are painted silver

After the war a new model code system was introduced, whereby radio models all began with R - the first model being the RA, a dual-wave 5-valve set commonly released in a pressed tin cabinet.