The Cromwell model 520 was manufactured for H. W. Clarke Ltd by Collier & Beale Ltd in 1940.

Other radios based on the same chassis:

5-valve dual wave radio.

No schematic held, possibly similar to C&B 5-LS?  Chassis info based on that, so take with a grain of salt.  If you have information to add, please do.

Actually, its referred to in literature as a C520 (even though the badge only states '520'), so please note that the service information has been updated to reflect that.

The C520 name could be to differentiate it in service literature from the Gulbransen version, which is referred to as the G425.

Technical Information

Valves (5 + magic eye on some): 6A7, 6D6, 6B7, 42, 80 and 6E5 on some

Intermediate Frequency: 465kc/s

Frequency Bands: 2

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

Service information cb-model-g425-and-c520-5v-dw-ac-1940.pdf

1940 Gulbransen  model 425

1940 Gulbransen  model 425

General Construction Notes for Collier & Beale Ltd:

Model numbering followed no real sensible scheme until around 1940 - and prior to 1934 apparently no model numbers were assigned at all.

From 1940 a 3- or 4-digit system was employed where the first digit indicates the number of valves, the second digit is the number of bands and the third is the year of manufacture.  From 1950 the last digit became two digits, eg: 5151 is a 5-valve broadcast-band only from 1951.

From 1957 model numbers were replaced with model names, ie the Pacemaker Buffalo - which makes the year of manufacture hard to determine unless service info is consulted (although C&B often released service info after the radio, and the date on the service info was for its release, not that of the model.

Other documented models using this chassis (2 in total)

1940 Gulbransen model 425 'Clipper'