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 receiver.

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 SX-88 chassis.

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.