HP200A

from Wikipedia, the free encyclopedia
Front view
Interior construction

The HP200A was the first product manufactured by Hewlett-Packard in David Packard's garage in Palo Alto in 1939. It is a tube-fitted audio frequency generator whose sinusoidal signal could be used to test electronic audio systems.

The device delivered 1 watt output power with an adjustable frequency from 35 Hz to 35 kHz. It consisted of two pentodes 6F6 and 6V7 in the oscillator part and a single-ended A output stage (6V6) with output transformer .

As a special feature, this oscillator uses a Wien-Robinson bridge with variable capacitors as frequency-determining elements and an incandescent lamp for amplitude stabilization. The temperature-dependent electrical resistance of this lamp (3 W 120 V, operated at around 3 V) creates negative feedback that is dependent on the cathode current of one of the oscillator tubes and prevents non-linear distortion of the sound frequencies generated. See also Vienna-Robinson Bridge # amplitude control .

The device is based on the Hewlett patent. A small incandescent lamp was already used here to stabilize the amplitude. This amplitude stabilization is a key method for the use of a Wien bridge for low-distortion sine oscillators, as these are not inherently stable.

The HP200B was later manufactured with a slightly different frequency range (20 Hz to 20 kHz). Tone generators based on exactly this principle, the same frequency range and also with variable capacitors, but later with transistors instead of electron tubes, were built until the 1980s.

The product name HP200A was chosen to give the impression that HP is already an established company. The first customer is Walt Disney Studios , which acquired eight HP200A audio frequency generators and used them in the production of the first cartoon Fantasia , which appeared in 1940 and was recorded in a multi-channel sound system .

Web links

Commons : HP200A  - collection of pictures, videos and audio files

Individual evidence

  1. http://www.hp.com/hpinfo/abouthp/histnfacts/museum/earlyinstruments/0002/other/0002patent.pdf William H. Hewlett's patent with circuit and more detailed description on page 2, left line 31ff.
  2. GF22 from VEB Präcitronic Dresden
  3. Laurie Pasiuk: Vault guide to the top tech employers . Vault Inc., 2006, ISBN 9781581313390 , p. 111 (Retrieved May 10, 2010).