Heathkit IO-12 Oscilloscope  
Written by AnubisTTP on 2007-04-03  


The Heathkit IO-12 is a single-trace vacuum tube oscilloscope. The IO-12 has horizontal and vertical inputs on the front panel, as well as a place to connect an external trigger. The IO-12 also has a z-axis input, though it is well-concealed. The user must unscrew a small metal hatch from the back of the unit to gain access to the z-axis connector. All connectors are the banana plug style common on older scopes, instead of more modern BNC connectors. The screen diameter is an ample five inches, and rotary knobs are used for all front panel operations. The horizontal frequency scale has two user presets, which can be set by inserting a screwdriver into a pair of holes on the right of the timebase control.


Like all things Heathkit, the IO-12 oscilloscope started its life as a box of capacitors, resistors, and other electronic minutae that the original owner would have been required to assemble, using the included instructions, into a working piece of test equipment. Since every piece of Heathkit gear was built by a different, random person, build quality of Heathkit equipment varies widely. Unlike most of the other Heathkit equipment in our possession, the IO-12 pictured here seems to have been competently assembled. All of the controls function properly and the scope displays accurate readings. Despite this, it is quite obvious that the device was assembled by someone with minimal training in soldering.

The display is a large RCA 5UP1 electrostatic deflection CRT that is securely supported at both ends. Wire bundles have been tied back for a clean assembly. Other tubes in the scope are spit into three distinct sections: a 12AU7, 12BH7 and 6AN8 on the rear board, a 6AB4, 6J6, 6C4 and 2 12AU7's on the lower board, and a 6CA4 and 1V2 mounted directly to the metal chassis.

Heathkit IO-12 Oscilloscope
Heathkit IO-12 vacuum tube oscilloscope.

Heathkit 10-12 Oscilloscope
The interior of the IO-12 is clean and fairly well designed, but not exactly HP build quality.

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