Hugh Hetherington Hearing Aid Museum
Hugh Hetherington Hearing Aid Museum

The Hearing Aid Museum

Hearing Aids of all types—Ear Trumpets, Carbon Hearing Aids, Vacuum Tube Hearing Aids, Transistor Hearing Aids, Body Hearing Aids, Eyeglass Hearing Aids and much more!

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Click on the "General Information" button (top button above) for an overview and general information on this category of hearing aid.

 

Vacuum Tube Hearing Aids: 1921-1953

Precision Table Aid Model 3AC21 Vacuum Tube Hearing Aid

The Precision Table Aid Model 3AC21 vacuum-tube hearing aid was made by the Precision Electronics Co. of Chicago, IL in 1948

The Model 3AC21 was Precision Electronics first and only hearing aid. It was a 3-vacuum tube model.

The Precision Model 3AC21 measured  8⅞" x 5⅛" x 5⅞" (22.5 x 13.1 x 15.0 cm) high and weighed 6 lbs 13 oz. (3090 g).

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Front view of the Precision Table Aid Model 3AC21 vacuum-tube hearing aid. This hearing aid looked much like a radio of the time. The microphone grill is on the left. The on-off/volume control is at the bottom center and the tone control is in the bottom right corner.


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Bottom right rear view of the Precision Model 3AC21 vacuum-tube hearing aid showing the Make and model. It's called a Precision Table Aid" and below that "A Desk Model Hearing Aid" and "Model 3AC21    115 Volt AC - 60 Cycle".

 


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Bottom right rear corner  view of the Precision Model 3AC21 vacuum-tube hearing aid showing the LO-HI switch of unknown function. It may be a Low or High power switch for people that needed more volume, or a low or high frequency bandpass switch.

 


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Bottom left corner view of the back of the Precision Model 3AC21 vacuum-tube hearing aid showing the ?serial number (12112). The power cord comes out directly below the serial number and the earphone jack is to the right.

 


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Rear view of the Precision Model 3AC21 vacuum-tube hearing aid showing the ¼" phone plug for the earphone.

 


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Rear view of the Precision Model 3AC21 vacuum-tube hearing aid with the earphone cord plugged in.

 

 


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Front view of the Precision Model 3AC21 vacuum-tube hearing aid's earphone. Note the 6 tiny holes around the periphery of the "circle" to let the sound out.

 


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Rear view of the Precision Model 3AC21 vacuum-tube hearing aid earphone. The headband is missing.

 

 


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Close-up rear view of the Precision Model 3AC21 vacuum-tube hearing aid earphone. Embossed on it are the words, "Receiver", "ANB-H-1", "Made in U.S.A. by Utah-Chicago".

 


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Rear view of the earphone of the Precision Model 3AC21 vacuum-tube hearing aid showing the model number (MC-162-A) of the rubber earphone cup.

 


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Rear view of the Precision Model 3AC21 vacuum-tube hearing aid with the wooden back removed to see inside. What gave this hearing aid most of its weight was the large power transformer (left).

 


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Inside rear left view of the Precision Model 3AC21 vacuum-tube hearing aid showing two of the three vacuum tubes. At the left is a Sylvania 6X5 GT vacuum tube and at the back (behind it) is a Raytheon 280  9-04 vacuum tube.

 


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Inside rear right view of the Precision Model 3AC21 vacuum-tube hearing aid showing the large electrolytic capacitor (right) and behind it, the black Radiotron 6J7 vacuum tube. The microphone (behind the round metal plate at the back) is connected to the grid cap of this vacuum tube. The Sylvania 6X5 GT vacuum tube is on the right.


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Bottom left rear view of the Precision Model 3AC21 vacuum-tube hearing aid showing the 9' 3" long (282 cm) power cord.

 

 


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Top view of the Precision Model 3AC21 vacuum-tube hearing aid. Since it was quite hefty, it had a strong handle—what looked like a cupboard door handle—for carrying it.

 


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Rear view of the Precision Model 3AC21 vacuum-tube hearing aid showing the 6 slots to dissipate the heat from the tubes..

 

 

 


 

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