Eico 377 Audio Generator

I bought this Eico Audio Generator at a local Ham flea market.

I did not have a real requirement for another audio generator but the price was right and I like collecting old test equipment. It came with 3 spare tubes (used) and an audio cable. A comprehensive manual is available on the BAMA website. A total of 5 tubes are used including a 6X5 rectifier. The generator was capable of either sine or square wave outputs.

Before powering it up I did a visual inspection of the circuitry and checked for any obvious shorts etc. I power it up slowly using a Variac on the ac line. The generator worked without doing any repairs. It was stable and surprisingly flat across the frequency ranges. I checked the sine wave output distortion using my HP Distortion Analyzer. It was typically less than 1% at the various output voltages and frequencies that I checked. The distortion was tested across a 1000 ohm load. The dial accuracy is OK but not great. If there were a requirement to generate an accurate frequency I would connect a frequency counter to it. The generator is stable enough to produce usable CTCSS (PL) tones but a counter is needed to set the frequency. The square wave performance is OK and seems to be optimal around 1000 Hz.

Sometime in the past someone modified the generator to include a 20 dB (voltage ratio) step attenuator. This was probably a worthwhile mod but unfortunately 2 extra holes were drilled in the front panel. The output jacks were also rearranged to conform with the standard 3/4" spacing. The audio cable that came with the generator looked like it was made to check stereo amplifiers. I am guessing that in stock form the generator could not be adjusted low enough in level or precisely enough for the application without some additional attenuation.

This generator has become my preferred generator for use over my HP oscillator. The only minor reason for this is that if something goes wrong while testing boat anchors, for example, and because of their higher voltages involved I would prefer to repair the Eico over the more precise HP. The Eico is also likely more forgiving. Overall the HP is a much better oscillator but the Eico is definitely a usable piece of test equipment.

I have four other pieces of Eico equipment. They are the Model 950B Capacitance Bridge, the Model 221 VTVM, the 720 H.F. transmitter with the 730 modulator.

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