HP 200CD Audio Generator (1955)
the Hewlett-Packard 200CD is a "wide range oscillator" that
generates a sine wave in the subsonic, audio, and ultrasonic frequencies
(5 Hz to 600 KHz). I bought my HP 200CD for one task:
aligning the second IF (intermediate frequency) section of my
Hallicrafters SX-88 communications
The SX-88's second IF stage operates at the unusually low
frequency of 50 kilohertz. My everyday signal generator can't
operate that low, but the HP 200CD produces a beautiful
sine wave at that frequency.
This photograph shows the 200CD in use. I'm using a multimeter
to double-check its output frequency and an oscilloscope to
view the waveform.
The next photo shows the generator during the alignment, next to my Hallicrafters
The 200CD is built like a battleship, like many Hewlett-Packard products
of the time. Since buying it for the Hallicrafters restoration,
I have occasionally used it when working on audio gear.
You can download the detailed HP
Operating and Service Manual from the hparchive website.
I own one other Hewlett-Packard device, a model
428B DC Milliammeter. It's roughly the same
size and shape as the 200CD, but it serves a very different purpose.