Hickok 277X Signal Generator restoration

The Hickok 277X is identical to the 288X, except that it omits the output meter (what Hickok calls the decibel meter).

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The Boatanchor Manual Archive (BAMA) has a good scan of the manual.

Hickok calls it a “Universal Crystal Controlled Signal Generator”. The “Crystal Controlled” part is a bit of marketing hype – it just has a built-in crystal calibrator.

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These Hickok generators remind me a bit of the General Radio Unit Instrument line. The Unit Instruments were essentially modules that the user was supposed to assemble into a custom test instrument. It took some skill to use them. 

The Hickok 288X/277X are similar in that the instrument contains a number of sub-modules along with switching to combine them in different ways. The user has to have some skill to apply the resulting combinations. Here’s the block diagram.

Hickok 288X block diagram

In addition to supplying unmodulated or AM modulated RF, the 288X/277X can output frequency modulated RF, frequency swept RF, a variable audio frequency, 400 Hz fixed audio frequency, a swept audio frequency, and modulated or unmodulated crystal calibrator RF at 100 KHz and 1 MHz. 

Here is the operation chart for the 288X/277X. Click the thumbnail for the PDF.

Hickok 288X chart

The FM modulated and swept RF, variable audio, and swept audio frequency signals are produced by beating the main oscillator against a second oscillator, either the FM oscillator in the block diagram or the 400 cycle audio oscillator reconfigured as a beat frequency oscillator.

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I picked this 277X up on Craigslist, restored it, and passed it on. I’m trying hard to avoid creating a Hickok test equipment collection.

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The resistors were in tolerance, or close enough, but the electrolytic and paper capacitors had to be replaced.

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I didn’t restuff the filter capacitor can on this restoration. Instead, I soldered a terminal strip to one of the ground lugs on the filter can. I mounted the replacement electrolytics on the terminal strip.

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I cleaned up the old hardware using a wire wheel on my Dremel Moto-tool.

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They cleaned up nicely.

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The dial window had broken loose from its mounting flange. Fortunately it was still rattling around inside the case. I glued it to the dial bezel with superglue.

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The power switch wasn’t working, so I had to remove it, open it up, and clean the contacts.

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All back together and working nicely. The frequency dial was still accurate.

© Steve Byan 2011-2019