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).
|
 |
Click picture for larger view |
| |
 
|
|
|
|
|
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.
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
|
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."
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
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).
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
|
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).
|
 |
Click picture for larger view |
| |
|
|
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)
|
 |
Click picture for larger view |
| |
|
|
Close-up top view of the Philco Model 912 table-top vacuum-tube hearing
aid showing how the earphone jacks were wired together.
|
 |
Click picture for larger view |
| |
|
|
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).
|
 |
Click picture for larger view |
| |
|
|
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.
|
 |
Click picture for larger view |
| |
|
(If a larger picture doesn't appear, you may have to
turn your pop-up blocker off)
|
|
|
