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Test – Connect a speaker or headphones to the "SPKR" jack. Apply power to the board.
Advance the volume control to maximum. Touch the top (ungrounded end) of diode D2; 60 Hz
hum should be heard coming from the speaker or headphones. Rotate volume control R80
counter clock wise (CCW) to verify the hum level changes. At full volume, jumper the pads
marked "KEY" and verify that the 60 Hz hum is muted.
Your Measurements/Observations - ______________________________________________
____________________________________________________________________________
Receive Audio Preamplifier
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Install transistor Q10.
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Install resistors R19, R20, R21, R22, R23 and R24.
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Install capacitors C27 and C28.
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Install tantalum (tan color, both leads on one end) capacitors C26 and C30 matching the polarity
markings on the case with those on the PCB.
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Install electrolytic capacitors C23 and C29 matching the polarity markings on the case with
those on the PCB.
Your PCB should look like that shown in the next figure.
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