The Columbus model 91 was manufactured for Columbus Radio Centre Ltd by Radio Corporation of New Zealand Ltd in 1950.

Other radios based on the same chassis:

Third of the 'Big Bandspread' models (the Model 75 was the first in 1940, the model 90 was the next, in 1948 and this models big improvement was push-pull output, perfect for high output.  Some of the console-model 91's came with a big Goodmans 12" speaker, but most had an EM 10" speaker (91P had a permanent magnet 10" version).

1950 Columbus model 91

The Listener 8 May 1953

Technical Information

Valves (7 + magic eye): 6SK7, ECH35, 6B8, 6SL7, 6V6, 6V6, 5Y3 and 6U5 Magic Eye

Intermediate Frequency: 455kc/s (to be confirmed)

Frequency Bands: 5

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

Notes on service material suggest HT is too high and to insert a 250Ω 10W wirewound just prior to the reservoir cap / field coil junction to drop the 300V to around 260V.  Also use 5V4 as 5Y3 is possibly stretched in this role.  Other notes on the schematics in the service PDF - some are difficult to read.

Service information (RCNZ_-_model_91_-_7V_PP_AC_-_1950.pdf) here

1950 Columbus model 91

1950 Columbus model 91

1950 Columbus model 91

General Construction Notes for Radio Corporation of New Zealand Ltd:

The first digit of the serial number typically indicates the year of manufacture of RCNZ chassis' (although not the decade - that requires a little knowledge of the valves, construction, etc). Sets from around 1934 onwards were often (but not always) constructed in a distinctive pressed 'baking pan' style chassis, seemingly unique to RCNZ.

Model codes beginning with a 0, for example the model 051, are Osram valve versions of the model without the leading 0. Technically the 0 should be an O (for Osram), however the digit 0 was used throughout the site before this fact was discovered.

The E suffix indicates a magic eye option is fitted (in models which were available with or without, such as the model 25).

A and B suffixes appear to be simply updates to the current model, R also appears to be simply an updated model ('R'edesign, perhaps?)

P indicates either a permanent magnet speaker version of a model which also came with an electromagnet speaker (the model 26 for example), or a portable model (like the model 694P).

N and M indicated miniature valve versions of a model which started with all (or a mix, ie: model 5) of larger valves. One of these two codes may indicate a transitional mixture of octal and miniature - clarification is required.

S often indicates a stereo model.  It can also indicate 'self-biased' in the transition period between back-biased and self biased sets where there were models with both methods employed (53S for example)

Finally, other suffixes and prefixes make occasional appearances in the RCNZ lineup - like the 66W (a variant of the long-running model 66) and the 75XA (a 10-valve version of the model 75 with a separate amplifier chassis).

Model nicknames are often sourced from either newspaper advertising, company literature or the NZ Radio Traders Federation official trade-in price books (Particularly Courtenay models from this publication)

Other documented models using this chassis (3 in total)

1950 Courtenay model 91
1950 Columbus model 91 'Warwick'