COLUMBUS 5B (CIRCA 1953)

The Columbus 5B was manufactured for Columbus Radio Centre Ltd by Radio Corporation of New Zealand Ltd in about 1953, production ran for 2 years.
This model is part of the RCNZ Model 5 series of radios.

Wider dial scale than the original model 5 or the 5M but otherwise appears to be very similar to the model 5M.

No loop aerial, this model has a compact aerial coil mounted to the back of the dial assembly.

Valves (5): Model 5
6BE6, 6BA6, 6AV6, 6K6 or 6V6GT, 6X5GT

Subsequent models:
6BE6, 6BA6, 6AV6, 6AQ5, 6X4

Intermediate Frequency: 455kc/s

Frequency Bands: 1

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

The model 5 lasted for a few years and was released in four different variants with two valve lineups.  The models were the 55A, 5B and 5M.

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.

 

Release notes for the Columbus model 5

1950 Columbus model 5 Schematic

1950 Columbus model 5 later schematic

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.

All documented models using this chassis (6 in total)

YEARMODEL NAME
1950Courtenay model 5
1950Columbus model 5
1951Columbus 5M
1953Columbus 5B - this set
1951Columbus 5A
1954Courtenay 5B