Later version of the model 5. Note also the factory (presumed) motel version with 6d coin slot.The Columbus 5M is part of the RCNZ Model 5 series of radios.
The first model 5's appeared in 1950, and the model lasted for around 4-5 years with various changes along the way. The first model used a mix of miniature and octal valves, but subsequent models used all miniatures. Externally they all looked much the same aside from the model 5B which had a slightly wider dial scale, and a slightly narrower speaker grill to make up for it.
By the mid-50's Radio Corporation of NZ was producing new plastic-cabinet radios like the 504 and 565, and this new versatile and colourful material was rapidly replacing timber as the cabinet style of choice - the model 5 being one of the last wooden mantle radios from Radio Corp NZ.
The radios in this series are:
1950 Courtenay model 5 Talisman
1950 Columbus model 5 Bristol
circa 1951 Courtenay 5M
circa 1951 Columbus 5M
1951 Columbus 5A Bristol
circa 1953 Columbus 5B
circa 1954 Courtenay 5B Talisman
Intermediate Frequency: 455kc/s
Frequency Bands: 1
Chassis Notes(most schematics can be clicked to download a full size version)
The model 5 was originally spec'd to use an octal 6K6** output valve, although its likely that most have a 6V6. There is also a release note stating it would most likely change to be a 6AQ5 in time. It also showed an octal 6X5GT rectifier. All subsequent models have a full miniature valve lineup. The early schematic showing octal output and rectifier valves has no date or drawing number and may be a lab drawing, or an unofficial release to meet requests from service departments around the country. A subsequently released 'Model 5' drawing dated August 1951, almost a year after the release note, shows all miniature valves. Its unclear if RCNZ was referring to the original model 5 or all available variants at that time (although not all variants had the shown loop antenna).
The later versions also had a better spread of the frequency band as can be seen in the comparison photo of the early model 5 dial and the later ones.
The model 5B has a wider dial, with a narrower speaker grill to compensate, and uses a standard aerial coil rather than the loop aerial the other models have.
**Of interest is the valve lineup provided by the release notice sent to Columbus Radio Centres (see below) - the output valve is listed as a 6K6, which may be updated later to a 6AQ5. The 6K6 is a lesser known cousin of the venerable 6V6 and RCNZ must have had a few of these rarer output valves for them to spec it into the set - although the official RCNZ schematic shows a 6V6GT. Of course, all subsequent variants of the model 5 used 6AQ5 miniature output pentode.
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).
|1950||Courtenay model 5|
|1950||Columbus model 5|
|1951||Columbus 5M - this set|