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

Philco Model 912 Table-Top Vacuum Tube Hearing Aid (disguised as a radio)

The Philco Model 912 table-top vacuum tube hearing aid was made by the Philco Corp. of Philadelphia, PA in 1939.

The Model 912 was Philco Corp's first and only vacuum tube hearing aid. It was a 4-vacuum tube model.

The Philco Model 912 measured  8⅜" x 5⅜" x 3⅞" deep (21.3 x 13.7 x 9.9 cm) and weighed 4 lbs 4˝ oz. (1940 g).

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Front view of the Philco Model 912 table-top vacuum-tube hearing aid. Philco disguised this hearing aid as what appeared to be a radio. Thus a person wearing earphones looked for all the world to be privately listening to a radio.


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Close-up view of the "dial" of the Philco Model 912 table-top vacuum-tube hearing aid. There it clearly states , "Philco" and below it "Hearing Aid"

This plastic plate replaced the dial of the normal Philco radio. Apart from this, it looked exactly like a radio, although if you think about it, the tuning knob is also missing.


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Front view of the Philco Model 912 table-top vacuum-tube hearing aid. The microphone grill is on the left. The on-off/volume control is at the bottom center and the tone control is to the right of it.


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Front view of the Philco Model 912 table-top vacuum-tube hearing aid showing the 6' long (198 cm) power cord (left).

Since it was quite hefty, it had a strong handle on the top for carrying it from place to place.


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Close-up view of the label on the bottom of the Philco Model 912 table-top vacuum-tube hearing aid showing the manufacturer (Philco), the model (912) and the code (121).  Below that "50-60 cycles" and "115 volts A.C. or D.C.  30 watts"

In the center is a diagram showing the placement of the 4 tubes. Below the diagram it reads, "To maintain original performance always specify genuine PHILCO tubes." and "To remove tubes, rock them gently in their sockets"

At the bottom is the year (39 for 1939) and serial number (7470) and "Printed in U.S.A."

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Inside front view of the Philco Model 912 table-top vacuum-tube hearing aid showing the loudspeaker which in this case was run "backwards" to make it into a microphone so there wasn't a separate microphone. To the right is a small light to lighten the "dial" just like it would have in a real radio.


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Inside top view of the Philco Model 912 table-top vacuum-tube hearing aid showing the power transformer (upper left) and below it a 7C6 vacuum tube. Another 7C6 vacuum tube is in the lower center. The microphone (loudspeaker) and associated transformer are on the right. On the extreme right is the 35Z3 rectifier vacuum tube (upper right) and 35A5 vacuum tube (lower right).

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Bottom inside view of the Philco Model 912 table-top vacuum-tube hearing aid showing the two large electrolytic capacitors (bottom left and right) and other electronic circuitry.

 


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Rear inside view of the Philco Model 912 table-top vacuum-tube hearing aid giving a different perspective of the components. Note the phenolic board with the 3 earphone jacks on it (left of center).

 


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Close-up rear view of the Philco Model 912 table-top vacuum-tube hearing aid showing the 3 earphone jacks. You either used two separate plugs for the red (1) and black (3) jacks, or, if your earphones ended in an RCA plug, you plugged it into the center jack (2)

 


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Close-up top view of the Philco Model 912 table-top vacuum-tube hearing aid showing how the earphone jacks were wired together.

 


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Rear view of the Philco Model 912 table-top vacuum-tube hearing aid showing the vent slots all across the upper back to dissipate the heat generated by the 4 vacuum tubes.

The earphone jacks are to the left of center, and the power cord comes out (bottom center).


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Close-up rear view of the bottom left corner of the Philco Model 912 table-top vacuum-tube hearing aid showing the number (27-9931) stamped there. Probably this was a part number.

 

 

 


 

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