Hewlett Packard 200CD Audio Oscillator

HP200 inside view

This is the more early HP200AB, with it’s 4 gang variable capacitor and octal tubes. The later model dropped back to a 3 gang capacitor and smaller tubes.

Service manual for Hewlett Packard 200CD Audio Oscillator with block diagram of the RC Bridge / Wien Bridge Oscillator, detailed operation and circuit schematic
This is a collectible item of test equipment today, beautifully built with it’s ganged variable capacitor and very low distortion output into 600Ω impedance, transformer coupled.
Please allow time for the PDF manual to load into Google Docs viewer. You can do a full screen view which is very clear

HP200 front view