COURTENAY MODEL 91 (1950)

The Courtenay model 91 was manufactured for Turnbull & Jones Ltd by Radio Corporation of New Zealand Ltd in 1950.

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).

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.

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).

All documented models using this chassis (2 in total)

YEARMODEL NAME
1950Columbus model 91
1950Courtenay model 91 - this set