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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