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Nagra I (1)

Country:  Switzerland
Manufacturer / Brand:  Kudelski SA; Cheseaux-sur-Lausanne
Year: 1951 ? Category: Sound/Video Recorder and/or Player
Valves / Tubes 4:
Main principle Audio-Amplification
Wave bands - without
Details Tape Recorder
Power type and voltage Dry Batteries / 2 x 1.5 & 135 Volt
Loudspeaker Permanent Magnet Dynamic (PDyn) Loudspeaker (moving coil) / Ø 2 inch = 5.1 cm
Power out
from Model: Nagra I - Kudelski SA; Cheseaux-sur-
Material Metal case
Shape Portable set > 8 inch (also usable without mains)
Dimensions (WHD) 300 x 150 x 110 mm / 11.8 x 5.9 x 4.3 inch

The Nagra I is a self-contained clockwork-driven  tape recorder using 1/4 " magnetic tape in reels of 5", powered by two batteries of 2 x 1.5 V for the tube filaments and one of 135 V.

During the year of 1951 Stefan Kudelski developed the Nagra I equipped with clockwork motor (Thorens) and low power electronic tubes. Kudelski sold some unities of the Nagra I for Radio Broadcast Stations and reporters with highly acclaimed success. At this time Nagra I was the most compact and best tape recorder for broadcasting reporters.

In 1953, in a new facility, Nagra began the production of the Nagra II (a Nagra I with the option to have an external modulometer [a kind of a VU meter] in the sidewall and a tape available /time recording indicator in front panel. Very few (5) machines were produced without silk screen printing on the chassis indicating the tape path.   Later in the end of 1953  Nagra, employing  only 7 workers, improves the Nagra II  to the Nagra II b and, after this, in 1955, to the Nagra II c (a Nagra II with some improvements in electronics  and using the first Nagra printed circuit).

In Nagra I and Nagra II tape transport is done using a mechanical spring (steel tape) motor (Thorens 144\F).  Electronics is hand wired within a very compact volume of 110 mm x 110 mm x 90 mm where the four tubes (pentodes), two DAF96 and two DL94, are assembled.

The spring motor provides about 6 minutes of continuous recording and the battery discharge in about 5 hours of continuous use of electronics. The recorder has a mechanical indicator of available tape (or recording time) that is based on the number of revolutions available of spring tape of the motor. 

With the help of the hand crank, the spring strength may be recharged. Rewind of tape is done manually by using a small key that can be plugged in a hole in the back of recorder.

Net weight (2.2 lb = 1 kg) 4.5 kg / 9 lb 14.6 oz (9.912 lb)
Mentioned in Clockwork-Driven Tape Recorders, by Roland Schellin

Model page created by Moisés Piedade. See "Data change" for further contributors.

All listed radios etc. from Kudelski SA; Cheseaux-sur-Lausanne
Here you find 48 models, 45 with images and 19 with schematics for wireless sets etc. In French: TSF for Télégraphie sans fil.