Photocell Phonograph Needle

162

01:29:02

Philco Engineers used tiny floating jewel in record groove to rotate a paper thin mirror ( shown as vertical switch) covered with vaporized aluminum to send audio light signals to photocell ( shown as NPN transistor) to increase sound fidelity and reduce sharp needle wear on records.

Design considerations: Lamp is a special gas-filled lamp to eliminate flicker which would register as hum at high frequency (1.8 MHz) to get rid of hum.  Note: bulb filament supports are extra heavy to prevent "howl" from filament shaking.

Circuit shown in simulator is inside head of pick up arm.

published 9 years ago

faceblast

9 years ago

ah I was wondering how records could be read optically instead of physical

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