Test Gear Teardown: HP 209A Oscillator

The HP 209A Oscillator generates sine and square waves over a range of 4Hz to 2MHz. It's a later-generation oscillator and features a moulded plastic front panel and plug-together PCB construction. I've already removed the outer case parts before starting the video. The schematic in the manual is dated 1968, and the date stamp inside the instrument is June 4th 1973. It's all discrete transistors (no ICs) in a Wien Bridge configuration. Unlike other HP instruments, there's no long rod-operated mains switch; instead, the mains transformer is always on and the front-panel switch just turns off the DC supply.