The N.Z. Vintage Radio Project

Valves (5): 6K8G, 6U7G, 6Q7G, 6V6GT, 6X5GT

Intermediate Frequency: 460kc/s

Frequency Bands: 2

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

The RA and RB chassis' were the first Radio Ltd designs to use a cord clamp rather than the previously used knot.  They were also the first Radio Ltd set to use a 6X5 rectifier.

The chassis was plated rather than painted as was previous practice.

Speakers on early models were EM, but this was quickly changed to use of a choke and PM Rola speaker with a diamond-shaped magnet. Later models used a Rola speaker with a round magnet.

The layout changed during production - notably the transformer is at the back on the right on some, and further forward with the output valve and rectifier at the back right.

On some later models the separate rectifier 6.3V winding was removed and the rectifier was run from the 6.3V winding for all other valves in the set.  Most likely this was a cost cutting exercise, however the 6X5 has a reputation for cathode shorts which could take out the power transformer, so this is not necessarily a good idea.  Anecdotal evidence suggests Australian (AWV) manufactured 6X5's were more robust than some of their US counterparts though.

Some models have different tuning parts meaning the dials are opposite (ie: some have the low end of the band at the bottom, some at the top)

Much of this information has come from Bill Farmer, who started work at Radio Ltd in 1945, by way of an article by Murray Stevenson in the NZVRS magazine in May 2000.

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.